Trading in soil carbon stocks

Soil carbon has become a hot topic, with carbon sequestration in soil a possible method for reducing atmospheric CO2. But this isn’t an easy task, and there’s a lot more to soil carbon than just sequestration. Here, we provide an overview of soil carbon flows and what they mean in the context of the global food system.

The term soil carbon refers to carbon stocks, in various forms, present in the world’s soil. Soil carbon can be organic (e.g. living or decomposing organisms, humus) or inorganic (e.g. carbon-containing minerals such as calcite).

The amount of carbon in the world’s soils is estimated in the region of 2500 gigatons, more than three times that present in the atmosphere and more than four times that in all living organisms. Organic matter in the soil, including soil carbon, is vital to good soil health, improving water and nutrient retention, maintaining soil structure and as nutrient sources for plant and microbial life.

Soil carbon content can be understood as the balance between carbon inputs and carbon losses. A major contributor to soil carbon inputs is photosynthesis. Plants capture atmospheric CO2, which is transferred below the soil surface via the roots. As well as contributing to the structure of the plant, some carbon is passed to rhizobial microorganisms, the microbial populations that live in close association with plant roots. As root structures and microbial populations in the soil grow, so too does the bound soil carbon.

Carbon can also be added to the soil through decomposing plant and animal material. The process of decomposition involves microbial respiration, which releases CO2 into the atmosphere, but some of the carbon in the decomposing material remains in the soil. The net balance between carbon inputs and losses to the atmosphere determine whether the soil carbon concentration increases or decreases.

However, further complexity is added to the system by other, abiotic factors. Soil composition, temperature, water content and erosion all influence soil carbon cycling. Naturally, this means that soil carbon stocks vary enormously between different parts of the world, from less than 1 tonne of carbon per hectare in desert environments to several hundred tonnes in tropical forests. Even within local regions, soil type can result in significant differences in soil carbon concentrations. This variation makes quantifying soil carbon challenging.

Agriculture directly influences soil carbon stocks. Clearing of land for agriculture, and tillage and cropping are generally considered to reduce soil carbon concentrations. However, this is not always the case: in certain systems, conversion of forest to grassland results in increased soil carbon concentrations, but it is uncertain how permanent this change is.

A number of activities exist that can increase carbon sequestration in the soil, or decrease the rate of carbon loss incurred by agriculture. Reducing tillage and soil erosion minimises carbon loss to the atmosphere or to waterways, while organic fertiliser application can add to the carbon input on agricultural land. The use of cover crops, which prevent leaving the soil bare between cropping cycles, can also help to maintain or even increase soil organic carbon.

The benefits of such practices are both local and global. Increased soil carbon benefits soil health, increasing crop yields in some systems. The benefits to soil structure of high soil carbon also allow for better retention of micronutrients, such as iron and zinc. This can result in higher concentrations of these mineral in crops, and thus in our own nutrition.

However, there are challenges in increasing agricultural soil carbon stocks in many areas. It is far easier to add to soil carbon in areas where the current concentration is low than in areas with relatively high existing stocks, which may be close to saturation with carbon. Moreover, it is easier for agricultural interventions to increase carbon concentrations in the upper layers of soil than the deeper layers.

Perhaps the greatest driver of recent interest in soil carbon is for its potential in sequestering atmospheric carbon emissions from human activity. Atmospheric carbon, in the form of CO2, is well known as a greenhouse gas. Thus, the possibility of using soil as a carbon sink is gaining momentum.

The potential of this possibility has recently been demonstrated in Australia. Australia has an existing Carbon Farming Initiative that provides the legislation for obtaining carbon credits by demonstrating increases in soil carbon on owned land. Recently, an Australian cattle farm sold carbon credits to Microsoft to the value of $500,000, obtained entirely from soil carbon sequestration from the management of the farm’s grazing land.

Schemes like the Carbon Farming Initiative have the potential to spread. However, in order to quantify changes in soil carbon stocks, it is essential to measure changes in soil carbon over time. This can be done by taking soil samples from a number of representative sites and quantifying the carbon present. These measurements can then be repeated to establish changes in soil carbon concentration over time. However, the wide variation in soil carbon even within a small area makes generalisation of carbon concentrations difficult. Currently, work is underway to benchmark New Zealand soil carbon concentrations, with a view to tracking changes in the future. This work will have to contend with the difficulties of varied concentrations, but may ultimately lead to some form of soil carbon credit system in New Zealand.

Study of soil carbon is benefiting from the interest sparked by the need to reduce atmospheric carbon concentrations. However, its importance to the global food system reaches beyond carbon sequestration. Healthy soils play a role in reducing the environmental impacts of agriculture by retaining nutrients and structure, and enabling optimum crop yield and nutrient content. In the future, the drive for carbon sequestration may also influence land management and provide another source of income for food producers.

Glossary

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GMO crops in the global food system

Genetically modified organisms (GMO) are already major contributors to the global food system since their commercial introduction in the 1990s. For example, over 90% of US corn and soy acreage is planted with GMO seeds. Despite this, the use of GMO is still controversial, with many individuals against their use and many authorities strictly regulating their production and consumption. Here, the arguments for and against GMO use in crop production are presented. 

GMO are defined as organisms, and products thereof, that are produced through techniques in which the genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination. 

The process in which GMO are created differs depending on the degree of modification required but generally, a desirable trait is identified in one organism that could be of benefit in another. The trait is studied and, if possible, the gene(s) responsible for the trait are isolated. These genes are then introduced to the target organism, either via bacterial or viral infection, where the microorganism carries the target gene into the organism for uptake, or by bombarding the organism with particles coated in the target gene. 

The outcome of the process is a GMO that expresses the desired trait isolated from the original organism. 

Advantages of GMO  

The ability to transfer desirable traits between distantly related crops that cannot be interbred has obvious benefits. Examples of GMO use include the ability to increase photosynthetic rate, develop crops that are drought-tolerant with increased yields, and produce crops with disease resistance, such as blight-resistant potatoes

Moreover, crops can be developed that have greater nutritional value than conventional varieties. There exists a long list of such biofortified crops, including cassava with increased zinc, iron, protein and vitamin A content, high lysine maize, high provitamin A rice, and corn with increased provitamin A and folate. These crops are of particular value in global regions where nutrient deficiencies are a high priority public health issue. 

One widely used GMO is Bt-maize. This crop takes its name from Bacillus thuringiensis, the bacterium that donated to the maize plant the trait of producing an insecticidal toxin. Thus, Bt-maize is more resistant to pest insects than conventional maize, leading to higher yields and reduced pesticide use. As a result, 82% of the crop grown in the US in 2020 was the Bt variety. 

Disadvantages of GMO  

The arguments against GMO are largely based on health and environmental risks. The approval process for GMO is nationally administered, so differs between countries. Largely, these processes are more rigorous than for conventional foods and assess both the health and environmental risks of the GMO. 

The World Health Organisation states that no negative health consequences of approved GMO have been shown to date. However, concerns and risks do exist. One health concern raised is the possibility of allergenicity being unintentionally transferred between organisms. An example of this was when early GMO researchers, hoping to increase methionine content, found that the main allergen from Brazil nuts retained its allergenicity after transfer into a GMO soybean. As a result, the GMO soybean was never released commercially and allergenicity is now an important consideration when selecting donor crops. 

From an environmental perspective, there is the possibility that the GMO crop itself, or the introduced gene via cross-breeding or gene transfer, could escape the farmed environment and become a pest. The implications of this would depend entirely on the nature of the GMO crop; for example, transfer of a herbicide resistance gene to a non-target organism could lead to difficulties in controlling its growth. Alternatively, GMO crops could outcompete other plants due to the introduced trait, resulting in decreased biodiversity with unknown downstream implications. While the risk of these unintended consequences is low, they should be considered in the design and management of GMO. 

Finally, some express the opinion that GMO are morally wrong, as they involve too great an interference with living organisms. Such a decision can only be weighed by the individual but will likely mean that a proportion of the population will continue to avoid foods containing GMO products. 

This avoidance is challenging given the ubiquity of GMO products in many foods and by the difficulty for a consumer in identifying GMO foods. Different authorities take different stances on GMO labelling. For example, GMO are not specifically labelled in the US, rather foods that contain ‘bioengineered’ ingredients must be labelled as such. However, specific food labelling for certain types of GMO is on the horizon. The EU has stricter rules, with a requirement for GMO ingredients to be listed on food packaging. However, major food retailers have previously been forced to change their GMO policies due to the increasing “risk of finding GM material in non-GM food”. 

Conclusion 

GMO are widespread in the global food system, but not equally distributed.  

Moreover, regulation of GMO production varies and is not always clear and explicit. There are countries, like the US, where GMO crop production is widespread. Contrastingly, 19 member countries of the European Union have previously voted to either partially or fully ban the use of GMO. In New Zealand, no GMO crops are commercially grown. These variations in use and acceptance will certainly limit investment and development of future GMO. However, there is the opportunity for countries that have a GMO-free stance to use this status to market their products at a premium. 

GMO crops generally result in decreased pesticide use, coupled with increased yields and profitability. Moreover, there are those that believe that GMO will be necessary to adequately nourish a growing population and to adapt production to changing climates. The risks of GMO largely relate to unintended and uncertain consequences that must certainly be properly managed if GMO use and development is to increase. 

This Thought for Food was written by Cody Garton, a summer intern from Pūhoro STEM academy

Glossary

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Saturated facts

For nearly 50 years it has been believed that saturated fat is linked to heart disease. However, the scientific evidence does not universally support this assertion and recommendations are being made to change dietary guidelines and public knowledge around saturated fat. 

In response to increasing rates of heart disease in Western populations in the mid-20th century, the results of epidemiological studies comparing diets in different countries suggested that saturated fat intake could be a risk factor. Minimising the intake of saturated fat-containing foods such as red meat, dairy and chocolate was advised as a result. Currently, the NZ and UK dietary guidelines recommend reducing saturated fat intake, while the US and Australian Dietary Guidelines recommend the restriction of saturated fatty acids (SFAs) to less than 10% of total calorie intake in order to reduce the risk of cardiovascular disease (CVD). 

Saturated fatty acids (SFA), colloquially termed saturated fat, are molecules found in many common foods, especially animal fats and certain plant oils. Saturated refers to the molecular structure of the fatty acids, which have only single bonds between the carbon atoms, which cannot bond with any more hydrogen: thus, saturated with hydrogen. 

The claim that saturated fats were linked to negative health outcomes was accepted by public health institutes such as the World Health Organisation and the American Heart Association, and quickly caught on as a widespread belief. This has become so ingrained that, despite evidence to the contrary, it is proving difficult to change nutritional guidelines and the opinions of medical professionals, nutritionists, and consumers.  

A recent study, published in the Journal of the American College of Cardiology (JACC), performed a meta-analysis of randomized trials and observational studies on saturated fat. It was found that there were no beneficial effects of reducing SFA intake on cardiovascular disease and total mortality. While it was found that SFAs do increase cholesterol in most individuals, they increase concentrations of large particles of low-density lipoprotein (LDL) cholesterol, which is less correlated with CVD risk than the small, dense particles.  

An important finding of this study was that health effects could not be predicted from the SFA nutrient group alone; consideration of the overall macronutrient distribution and food matrix was necessary. Different SFAs have different physiological effects, which are further influenced by the foods they are found in and the carbohydrate content of the diet. Several foods relatively rich in SFAs but also rich in other nutrients, such as whole-fat dairy, dark chocolate, and unprocessed meat, were not associated with increased CVD or diabetes risk. 

There are calls to examine the overall risks of foods containing SFA, rather than SFA themselves. Likewise, the replacement of SFA-containing foods with those containing other fatty acids, often recommended in nutritional guidelines, was found unlikely to reduce CVD events or mortality. The authors of this last publication warned that current recommendations to replace SFA with alternative fatty acids may hinder efforts to get people to adopt more beneficial lifestyle changes, thinking that this single dietary change may be sufficient to reduce their CVD risk. 

One of the studies included in the JACC meta-analysis was the PURE (Prospective Urban Rural Epidemiological) study of 135,000 people from 18 countries on five continents. It found all types of fat (saturated, mono-unsaturated and polyunsaturated) were not associated with CVD, and saturated fat had an inverse association with stroke. Additionally, fat intake was associated with lower risk of total mortality. In contrast, a diet high in carbohydrates was associated with higher overall mortality risk.  

The claims around the negative consequences of fat intake may themselves have caused health problems. Reduction of saturated fat in the diet can lead to excessive consumption of carbohydrates as a replacement. Prevalence of obesity and type 2 diabetes has exploded in recent years, as seen in the chart below. Dr James Muecke, 2020 Australian of the Year, wrote in the Canberra Times“A flawed dietary guideline, which we have obediently and blindly followed for 40 years, is literally killing us. We’ve been encouraged to eat less fat and consume more carbs and yet we’ve never been fatter, our teeth never more rotten, and type 2 diabetes and its complications never more prevalent.” Dr Mueke makes clear the far greater need to prioritise reductions in excess carbohydrate consumption, rather than reductions in fat, to reduce the rate of non-communicable diseases in developed nations like Australia.

Rapidly increasing prevalence of obesity globally over the last 40 years. Source: World Health Organisation

In addition, advice to reduce consumption of nutrient-rich foods such as dairy and meat risks limiting the intake of nutrients such as calcium, iron, zinc, riboflavin and Vitamin B12. The Global Burden of Disease study shows that in the main, global health problems are caused more by what people do not eat – either through poor choice or through lack of choice – rather than an excess of certain foods. With the exception of excess sodium, the highest association of mortality and disability-adjusted life years globally was with insufficient intake of nutrient-rich foods. The study also showed the problems of consuming excess sugars. Consuming calorie-rich but nutrient-poor foods (e.g., sugary drinks) can displace nutrient-rich foods in the diet. The Global Burden of Disease study demonstrates that diets low in nutrient-rich foods are correlated with higher mortality. Importantly, saturated fat intake did not appear with any link to higher burden of disease. 

Number of deaths per 100 000 population attributable to individual dietary risks at the global level in 2017. Reproduced from the Global Burden of Disease study.

It is important for policy makers and health institutes to take all evidence into account when- designing nutritional guidelines. Arbitrary recommended intake levels for saturated fat will be less useful for the prevention of CVD or reduced mortality than targeting excess consumption, particularly of carbohydrates, and micronutrient deficiencies. Foods containing saturated fat, such as meat and dairy, can contribute to a nutritious balanced diet. They certainly should not be removed from the diet due to their saturated fat content, which has inconsistent links to modest impacts on CVD. Replacing these foods with carbohydrates will likely cause greater damage. 


Glossary

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The requirement for balanced global diets that connect 9 billion consumers


Wayne Martindale, Associate Professor of Food Insights and Sustainability at the University of Lincoln, provides a perspective on sustainable diets and how we should think about them.

The food and beverage system functions globally; we all source our meals from a global marketplace. The responsibility for a nutritious and balanced diet begins with producers and manufacturers before it is presented to consumers. The flow of foods and ingredients in the global food system provides many surprises.  

This article is a viewpoint from Europe and the United Kingdom, where our nation is soon to realise the impact of globally sourcing our food. Sustainability and security are inseparable attributes here and we believe a sustainable diet must provide balanced nutrition and security. This article will develop this relationship using existing evidence and demonstrate that limiting the discussion to a single attribute of sustainability such as greenhouse gas emissions, biodiversity or land use change will only result in polarised debates that will never get us to where we need to be. 

Best practice in the food and beverage industry has been transformed by sustainability. It resonates across industry and consumers as an ideal we should rightly strive to achieve. Much of what we have been aiming for is to reduce the greenhouse gas emissions associated with the production and consumption of foods. Manufacturers are now reporting carbon zero product categories including whole milk and beef, which was unthinkable ten years ago. Our improved understanding of how resources flow through food systems has made carbon zero a reality. Programmes that sought to reduce greenhouse gas emissions ten years ago exposed many gaps in our understanding of food systems.  

The initial debates tended to demonise food and beverage products with higher carbon footprints – namely livestock products and beef (Cederberg et al., 2011). What these studies did not consider was nutritional delivery and consumer experience, both of which are important because without them sustainability will never be delivered (Haddad, 2018). This is because every meal must deliver balanced nutrition and a favourable experience. If it does these two things, it is more likely it will result in optimal health and not be wasted. I was working with CSIRO in Melbourne as a McMaster Fellow when I realised that these relationships were critical. This was in part due to the publication of the Total Well Being Diet (TWD) book by CSIRO (Noakes and Clifton, 2005). What influenced me here was the fact that a formalised and scientifically formulated diet for health – the TWD – could resonate so strongly with consumers that a Government Science Agency publication on dietary change became a best seller! In the UK, this was only achieved by our best celebrity chefs, with the science part often in second place for editorial decision making. The TWD demonstrated the requirement for a healthy diet is clearly resonant with consumers. The notion of what is a sustainable one was less so, but it raised the issue of whether the two are related in any way? 

The issue of sustainability in food has often been associated with carbon footprint. The first studies of crop and livestock production that calculated what we now recognise as a carbon footprint were reported over 20 years ago (Brentrup et al., 2000). These were transformative in that they identified production processes that could reduce greenhouse gas emissions. In the case of agricultural products, their application resulted in reductions in diesel and fertiliser nitrogen used in sustainable farming.  

However, in terms of guiding responsible consumption, carbon footprints can be cumbersome. Such direct measures of carbon footprints for food lead to comparing livestock and plant proteins without considering any dietary requirements. Consumers are often told to not eat specific products, with beef being the main target for such attacks. This leads to a ‘stand-off’ in the sustainability arena, stifling innovation in manufacturing. Nutrition, consumer experience and taste all play an important role in quantifying what is sustainable, and they need to be accounted for when we place carbon footprinting into diets, meals and lifestyles. 

Carbon zero thinking has been transformative in breaking this deadlock and the launch of branded zero carbon livestock products such as whole milk, beef and lamb have shown that food producers and manufacturers are confident in claiming it (read more here). The subsequent re-thinking of carbon footprinting is enlightening because it can be related to achievable and nutritious diets and lifestyles so that responsible consumption is possible.  

Plant products typically have a lower carbon footprint than livestock products. Converting plant protein into livestock protein as efficiently as possible often means an increased carbon footprint. But even here there are exceptions. For example, rice has a greater footprint than whole milk (Clune et al., 2017). This is because of the requirement to flood and drain the soils used to grow rice, resulting in methane emissions (Burney et al., 2010). 

Consideration of production volume can provide a transformative view of the global food system carbon footprint. Production of the ‘big four global commodity crops’: rice (0.7 billion tonnes per year), wheat (0.7 Bn t/yr), maize (1.0 Bn t/yr) and soy bean (0.3 Bn t/yr) account for around 2.8 billion tonnes of production each year (Clune et al., 2017). Three of these crops have a carbon footprint of 0.5 tonnes CO2-equivalent per tonne production, and rice has 2.6 tCO2-e/t, summing to 2.8 Billion tCO2-e associated with the big four each year. The mean or average carbon footprint for beef globally is around 25 tCO2-e/t, some 50 times that of wheat, maize and soybean crops, used for both feed and food. However, only 64 million tonnes of beef are produced globally each year, which accounts for some 1.5 Bn tCO2-e. The GHG ratio of the ‘big three’ (‘big four’ excluding rice) to beef is therefore not 50 but 1.5! If we include rice, beef has half the global carbon footprint of the big four crops. This means we are being mis-led by slavishly following carbon footprint data alone. 

There is also much more here, in that a number of studies on beef for the reported average carbon footprint include the prime production of Wagyu beef under extremely intensive conditions (beer and massages) that holds no resemblance to grass fed and finished beef systems including typical Wagyu systems. The issue of production volume together with variation in carbon footprint data is overlooked in simplistic carbon footprint assessments. If we include variation in livestock production systems, the idea of a typical carbon footprint becomes unrealistic at best! Moreover, the spotlighting effect of carbon footprint will often leave the issue of nutrition aside and this is another reason there is a requirement to look at how carbon footprints of food are measured.

If we were to eat the lowest carbon footprint food group per calorie it would be cake and confectionery alone, because these foods have a carbon footprint of around 80 gCO2-e/100 kcal, whereas fruit and vegetables produce over 400 gCO2-e/100 kcal (Drewnowski et al., 2014). This is surely the opposite to what we are told as consumers. Milk and dairy products are in the middle of this range, lower than meat. And this is only considering calories; considering other essential nutrients such as protein would likely paint a different picture again. The dietary context for carbon footprint clearly needs to be clarified and that is why the Sustainable Nutrition Initiative seeks to find methods of providing robust evidence that will guide realistic, sustainable consumption that provides good health. 

An improved ability to access data has brought energy balance and carbon footprinting into the consumer goods arena and the drive for carbon zero is creating much innovation in food and beverage. It has brought sustainability closer to the consumer in that the consumption of a nutritionally balanced diet can be delivered sustainably even if we do not choose or eat food based on carbon footprints.  

It is important that improvements do not get lost in purely carbon footprinting diets. We are developing models for the UK that identify where critical points and connectivity in the food system control resource flows (Martindale, Duong, et al., 2020). These can be integrated with the nutritional insights of the DELTA Model developed by the Sustainable Nutrition Initiative and build on established indices of food sustainability. New Product Development (NPD) is the operational activity we are focusing on because, if product developers and technologists build in sustainability at the concept stages, there is an increased possibility that the final product will deliver it (Jagtap and Duong, 2019). One of our models – Centreplate – is currently being tested with respect to NPD strategies, improving protein supply and reducing waste (Martindale, Swainson, et al., 2020).  

We are currently at a point where food system insights have the potential to bring sustainability and nutritional datasets together because of two technological advances we would consider most notable. The first is the ability to embed digital technologies into resource packaging so that traceability and analysis of supply chain data can be enabled securely for most food companies (Martindale et al., 2018). The other is the projection of dietary impact of nutrition on populations. This changed forever a generation ago in response to the newly sequenced human genome. What followed was a scramble for therapeutics but the interaction of health and nutrition through our diet was largely overlooked (King et al., 2017). We now have a greater understanding of how genes and metabolism interact with what we choose to eat. It is essential to keep the food system lens, and this is what the Sustainable Nutrition Initiative’s DELTA Model does. Connecting datasets and making sure we speak to each other is becoming increasingly important. This is otherwise known as interoperability in the digital arenas. We have the capability to deliver a net zero sustainable food system, but without interoperability it will not happen. 

Our food future depends on all partners in the global system connecting methods and data that will guide sustainable dietary choices. At present the sustainable diet arena is noisy and confusing for many consumers because polarised views can dominate. This is why actions such as the Sustainable Nutrition Initiative are so important; they lay bare facts and guide routes to sustainable and secure global consumption that still provide the choice and experience that consumers require.

Wayne Martindale directs the Food Insights and Sustainability Service at the National Centre for Food Manufacturing at the University of Lincoln. Wayne has been working in sustainability since 1998, after eight years of doctoral research in biochemistry in the UK, Japan and USA. He started his sustainability practice with the BASIS/FACTS leadership team delivering certification programmes for UK agriculture and has held visiting scientist roles at CSIRO Australia and the OECD in Paris.


Glossary

Photo courtesy of Wayne Martindale.

Protein: we need quality, not just quantity


Getting enough protein in our diets is essential for adequate nutrition. What is less well known is that protein represents a group of nutrients, the amino acids, each of which needs to be consumed in sufficient amounts. Here, we look at how we digest protein, the importance of amino acids, and show that protein quality, not just quantity, is vital.

Protein, alongside carbohydrates and fat, is one of the dietary macronutrients found on the nutrition label of all commercially-produced food. The recommended daily intake (RDI) for protein on these labels varies between authorities, but is usually around 50 g. This allows food companies to easily calculate and display on packaging what percentage of your protein RDI is supplied by their product.

But what is meant by ‘protein’ on these labels? And where do these RDIs come from?

Protein and amino acids

Proteins are a group of molecules essential to all life, distinguishable from carbohydrates and fats by containing nitrogen. The use of proteins in our bodies is broad: they form our tendons and ligaments as collagen, break down our food as digestive enzymes, and protect from infection as antibodies, among many other roles.

Every protein is composed of a string of smaller molecules, amino acids, folded into a functional shape. The amino acids in the string and the folded shape of the protein are specific to the function of that protein.

When we discuss protein as a dietary macronutrient, we are really referring to the supply of amino acids in the foods we eat, rather than the protein per se. The protein content seen on food packaging should really be seen as the sum of the amounts of each amino acid in the food.

Protein digestion and use

Protein is present in the majority of foods we eat. The amount and type of protein varies depending on the food, but all are subjected to the same digestive processes once eaten.

Protein digestion begins in the stomach. The body produces the enzyme pepsin, which starts the breakdown of proteins with the help of the stomach’s acidic conditions. Digestion continues in the small intestine, with the enzymes trypsin and chymotrypsin continuing the breakdown of proteins to individual or very short strings of amino acids (dipeptides and tripeptides).

These small molecules, rather than the original proteins, are absorbed by the intestine and transported around the body in the bloodstream. Once absorbed, amino acids are used to construct the many proteins needed by the body.

Consuming adequate protein in the diet is essential. Our bodies do not store protein in the way we can store fat or carbohydrates. Instead, there is a constant cycling of protein construction, breakdown and excretion. This protein turnover cycle leads to around 250 grams of new protein being produced each day, either using recycled amino acids from body protein breakdown, or from the amino acids derived from newly digested dietary protein. If dietary protein is lacking, this can lead to an overall depletion of body protein over time.

The importance of each amino acid

The most common way of calculating protein RDI is by bodyweight. For example, a frequently heard recommendation is that you should eat 0.8 g of protein each day for each kg of bodyweight. Thus, a 75 kg man should consume 0.8 x 75 = 60 g of protein each day. However, there is a lack of consensus around the value of 0.8 g, with many arguing that intake should be at least 1 g, particularly for athletes and older adults.

This calculation around protein RDI hides the more specific amino acid requirements of the body. There are 20 common amino acids, 9 of which are essential. Essential means that the body cannot effectively make these amino acids itself, so must obtain them from the diet.

There are RDIs for each essential amino acid, based on the amount required for body protein production. However, these RDIs are not displayed on food products, as this would be difficult to calculate for each food and make understanding nutrition labels more difficult. Instead, the protein RDI approximates what is needed based on the amino acid content of an average diet. This approximation was designed for a population that consumes a diverse diet over time. It is less fitting for day-to-day protein consumption of the individual, particularly those who consume only a limited range of protein sources. As an individual, it’s important you obtain enough of each essential amino acid each day.

What happens if we don’t get enough of a certain amino acid?

The result of deficiency in amino acids is best explained through an analogy.

Imagine you are assembling toy cars. The process involves painting the body of the car green, and then putting on the wheels. You have a box of car bodies, a pot of green paint, and a box of wheels.

As you are assembling these cars, you come to a point where you still have car bodies and wheels, but you have run out of green paint. However, with a little more effort, you can make more green paint by mixing some blue and yellow paint you have. With this newly made green paint, the assembly process can continue.

However, if you come to a point where you have car bodies and paint, but have run out of wheels, you cannot continue to assemble the cars. No matter how much of the other two components you have, the wheels are essential, so car assembly must stop until you have more wheels.

The construction of the toy cars from components is analogous to the construction of a protein in the body from individual amino acids. In the assembly of a protein, several different amino acids are required. Like the green paint, if the body runs out of a non-essential amino acid, then it can produce more from other amino acids, although less efficiently. However, if the body runs out of an essential amino acid (those that must be derived from the diet), protein synthesis is halted – much like running out of wheels in the toy car assembly.

If you do not obtain sufficient essential amino acids from your diet, synthesis of necessary proteins can be halted. The wheels in the toy car analogy are the ‘first limiting’ component in car assembly. In humans, it is often the amino acid lysine that is the first limiting amino acid to protein synthesis. This is because lysine is required in a large number of proteins and is not always readily available from the diet. A person can be protein deficient by being deficient in just one essential amino acid, regardless of the amount of the other amino acids they consume. And since the body is unable to store protein, an excess of unused amino acids consumed will be wasted by the body when it cannot immediately use them. Getting enough of each essential amino acid is required for optimal health.

How do I ensure I get enough of each amino acid?

Different foods contain different distributions of amino acids. For example, chickpeas are higher in lysine than oats, but the reverse is true for the amino acid cysteine. Plant foods are more often limited in certain essential amino acids than animal foods, due to the similar proteins required by animals and our own bodies. If plant-sourced foods are your main source of protein, it is important to understand their amino acid profile. Plant foods with complementary amino acid profiles can be consumed together to make up for their individual deficiencies.

Another important consideration is amino acid bioavailability; the percentage of the total amino acid that is available to the body from different food protein sources. The efficiency of the protein digestion process varies depending on the structure of the protein consumed and the food matrix proteins are contained in. Extensive research has been performed on the bioavailability of each amino acid in human foods. The table below gives a summary of bioavailability values for some selected foods.

FoodAmino acid bioavailability
(% of total consumption that is absorbed)
Roasted beef94 – 99  
Fish81 – 94
Cooked kidney beans64 – 100
Oats70 – 88
Potatoes47 – 66
Rice75 – 99
Skim milk78 – 97
Cooked soyabeans71 – 90

Bioavailability of amino acids can vary widely between foods. Therefore, it is useful to have a score for each food reflective of the overall amino acid availability, commonly referred to as protein quality. The DIAAS score (Digestible Indispensable Amino Acid Score) is recommended by the UN Food and Agriculture Organisation for this purpose. The digestibility of each essential amino acid in a food is calculated and compared to a reference protein, and the DIAAS is the lowest of these calculated values. The score is thus reflective of the digestibility of the most limiting essential amino acids in the food.

A DIAAS score of 100 or more indicates excellent protein quality, with high digestibility of all the essential amino acids. Scores between 75 and 100 are considered good sources of protein, but consuming complementary proteins would improve their profile. Scores below 75 are of lower quality. Some example foods with their DIAAS are given below.

FoodDIAASLimiting amino acid(s)
Beef (roasted)99Leucine and Valine
Pea protein concentrate82Methionine and Cysteine
Rice (cooked)60Lysine
Skim milk powder105Methionine and Cysteine
Soya protein isolate84Methionine and Cysteine
Wheat45Lysine

Generally, animal-sourced foods have higher DIAAS scores than plant-sourced foods. This means that the profile of amino acids is better suited to human digestion and to fulfilling our needs for protein synthesis.

At a global scale, producing enough of each amino acid is critical to the ability of the food system to meet nutrient needs. When considering possible future scenarios, the DELTA Model predicts the supply and bioavailability of essential amino acids, as well as total protein.

Take home message

The single macronutrient protein consists of a group of essential nutrients: the amino acids. These molecules are what is needed in our diet to construct the diverse body proteins, essential to bodily function, health and life.

Getting enough protein in your diet is not just about reaching the protein RDI. Instead, you need to reach the RDI for each essential amino acid. This is most easily achieved by eating high-quality protein, or combinations of protein sources with complementary amino acid contents.


Glossary

References for DIAAS values: 1, 2, 3, 4

Green car photo by MW on Pixabay. All other photos courtesy of the Riddet Institute.

Microbiomes and Sustainable Nutrition


Did you know that around 10% of your daily energy intake is supplied by intestinal microbes? Or that many plants and animals that we rely on for food are dependent on microbes for their survival? Although the connections between the microscopic world and the global scale of sustainable nutrition are not obvious, microbes play a significant role in the way our food is produced, processed and digested.

The term microbiome refers to a collection of microbes in a certain location. For example, the human gut microbiome consists of the microbial population living in our intestinal tract, which is receiving increasing attention as we recognise its importance in human health.

Microbiomes exist in diverse locations, many of which form part of the global food system. The role of these microbiomes in delivering sustainable nutrition for the global population is increasingly clear.

Cereal crops are a staple food source for the global population, providing predominantly energy and protein. These crops rely on soil nutrients, such as nitrogen, to grow and produce the protein we then consume. Often these nutrients are applied to cropland as fertiliser, produced either industrially or from animal sources. Management of fertiliser application is essential to avoid environmental damage caused by excess nutrients in soils and waterways.

Nitrogen can also be captured directly from the air by soil and root microbiomes, and microbes associated with roots can increase the availability of micronutrients to the plant. These microbes also increase the resistance of crops to soil pathogens. Moreover, soil microbes play a role in reducing soil erosion by producing products that bind the soil together. Current soil microbiome research is tackling the problem of reduced crop yields due to microbiome depletion and working to understand how the beneficial impacts of soil microbes can be harnessed. Learn more

In addition to plant-sourced food products, microbiomes are essential in the production of animal-sourced foods. An example of this is the rumen microbiome. Much of the forage consumed by ruminants cannot be digested by the animal’s own digestive enzymes; instead, the action of rumen microbes converts resistant plant matter, such as cellulose, to nutrients that can be absorbed by the animal’s digestive tract. These microbial products form the majority of energy intake for many domesticated ruminants. The action of the rumen microbiome is thus an important step in converting inedible plant material into animal-sourced food products in our own diet.

Rumen microbiome research currently has a strong focus on minimising the production of methane, a greenhouse gas and by-product of digesting plant material, by the rumen microbiome. This research is unpacking what causes certain microbiomes to produce less methane than others, and what the impact of different animal feeds is on methane production. Learn more

Continuing along the food supply chain, microbes are responsible for the production of common fermented foods. Fermented foods include cheeses, yoghurts, kimchi, sourdough and fermented meats, and are produced via the introduction of microbial populations to the raw food material. Apart from changing the taste, texture and appearance of these foods, the fermentation process enables perishable foods to be stored for longer periods, which can reduce food waste. The nutritional value of fermented foods is also enhanced in many cases. For example, the fermentation of cabbage to sauerkraut results in vitamin B12 synthesis, a nutrient not available in unfermented cabbage. There is also the probiotic capacity of fermented foods: their consumption can introduce beneficial bacteria to the human gut microbiome. Learn more

Microbiomes continue to play a role in the food system even after food is eaten. Although there are microbiomes in different sections of the human digestive system, the gut microbiome is intensively studied for its impacts on human nutrition and health. The make-up of our microbiome is in part determined by our diet, which forms the major food source for intestinal microbes. Just as our own ten trillion human cells require the nutrients we eat to carry out their function, so too do our equally numerous microbial cells. Current research is demonstrating increasing links between gut microbiome composition and various outcomes for human nutrition and health. This includes links to energy and nutrient yield from the diet, roles in intestinal disease and even impacts on brain function and mood. It is now recognised that we cannot have a full appreciation of human nutritional health without consideration of the gut microbiome. Learn more

A sustainable food system is one that ensures food security and nutrition for all, without compromising the future of the economic, social and environmental bases that the system depends on. Microbiomes are a critical element of a sustainable food system. Soil microbiomes enable and enhance crop growth, while playing a protective role in minimising the environmental damage of farming. Animal microbiomes are essential for the conversion of inedible plant material to animal-sourced foods, essential for food security in many developing parts of the world. Fermented foods are an integral constituent of the diet in many cultures and provide a means of preserving perishable foods, as well as adding nutritional and financial value. Finally, the human microbiome in part determines the nutrition we obtain from the foods we eat.

Microbiomes are present throughout the food system, and touch on all aspects of sustainability. As such, designing sustainable food systems for the future must involve consideration of the microbial element.


Glossary

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Build a food system from nutrient rich foods first


The philosophy of the Sustainable Nutrition Initiative (SNI) is to help create a better understanding of our food systems and identify opportunities for improvement. This is to ensure that in the future we can sustainably feed the global population. SNI has developed a modelling approach to test any range of possible scenarios that could contribute to globally sustainable food systems; The DELTA Model. This Model is unique because it explores the ability of different food production scenarios to provide the bioavailable nutrients needed to adequately feed the global population. The Model does not try to identify or prescribe options for diets for individuals, as there are many ways individuals, particularly those with money and access to different food types, can meet their nutrient requirements. Rather, it enables the creation of scenarios to inform discussions about possible future food production systems that meet the nutrient requirements of the entire population.

A critical feature of a sustainable food system is that the food produced is sufficient to provide the bioavailable nutrients required by the global population. However, there are imbalances in the production and consumption of these nutrients, causing a range of health issues. There is also sub-optimal use of resources, including environmental resources, to produce and distribute food. Globally, the current food system provides sufficient energy and macro-nutrients, but not sufficient micro-nutrients and trace elements, to meet global requirements. Therefore, production and consumption of nutrient-rich foods, particularly those that address micro-nutrient and trace element deficiencies, should be a priority.

There is an increasing challenge to feed the world within global resource constraints

The target of the global food system is to meet nutrient requirements of the global population. This includes all nutrients that humans must obtain from their diet to survive and thrive; energy, macro-nutrients – including essential amino acids as part of overall protein, micro-nutrients and trace elements. However, the earth has limited resources. There is a limit to the amount of food that can be produced before we run out of land, water and other resources. Not all food production scenarios are practical within these constraints. It is therefore a challenge to use resources optimally to ensure all nutrient requirements are met.

The global food production system produces enough energy to feed the world, but problems arise from lack of choice or poor choice

The current food system already has sufficient, even an abundance of energy and macro-nutrients to feed the global population. According to FAO, the world produces around 2,900 calories, 83 grams of protein, and 84 grams of fat per person, per day. This is more than enough to meet the average human requirements. There are however imbalances in the production and consumption of such nutrients. The reason that 11% of the world is undernourished is because of the inequality in access to food (distribution and affordability), rather than production scarcity. Other health issues caused by an under or over consumption of energy arise from a lack of choice or poor choice.

There is not enough production of some micro-nutrients to feed the world

While there is evidence that global food production can feed the world on a calorific basis, the micro-nutrient and trace element requirements of the global population may not be able to be met, even with perfect distribution and zero waste.

According to WHO, an estimated 2 billion people have a micro-nutrient or trace element deficiency (including clinical and sub-clinical deficiencies). Micro-nutrient and trace element deficiencies are common contributors to poor growth, intellectual impairments, and increased risk of morbidity and mortality. This is often referred to as ‘hidden hunger’; it doesn’t always cause death in the way protein-calorie hunger does. Instead it often results in individuals ‘surviving but not thriving’. Long-term consequences occur not only at the individual level but have detrimental impacts on national economic development and human capital. The most common deficiency is iron which affects a quarter of the global population. In some cases, these deficiencies are due to poor dietary choice, but others are due to a lack of choice resulting from limited access.

The DELTA Model shows that if all food that is currently produced was distributed evenly globally, there would still be shortages against requirements for some micro-nutrients and trace elements such as calcium, iron and zinc. In other words, the global food production system currently cannot provide sufficient micro-nutrients and trace elements to feed the world. This indicates resources are not being used to produce food that is optimal for meeting human requirements.

The food system should prioritise nutrient-rich foods

To ensure that the food we produce has sufficient nutrition to feed the global population, while still staying within the constraints of planet earth, nutrient-rich foods should be prioritised. The food system should be built from foods that deliver highly bioavailable quantities of micro-nutrients. This is particularly important for the nutrients in short supply (like calcium, iron and zinc), but as part of an overall nutrient-rich profile.

For example, the richest and best-absorbed source of calcium is cow’s milk and its derivatives. Other foods show high concentrations of calcium; however, bioavailability is variable. Milk is an efficient source of calcium in the food system. But the real benefit lies in dairy being a balanced source, rich in multiple nutrients other than calcium, including high-quality protein, zinc, vitamin B12 and riboflavin.  

For iron, the best sources come from animal-sourced foods, including red meat. This is because the bioavailability of haem iron from animals is much greater than non-haem iron from plant sources. Haem iron also helps the absorption of non-haem iron. Therefore, it is important to have sufficient red meat, alongside plant-sourced foods in the system to meet global iron requirements.

Of course, animal-sourced foods are not the richest source of every micro-nutrient and trace element. For example, vitamin C is best sourced from plants. The key is that starting with foods rich in bioavailable nutrients helps to ensure the global nutrient requirements are met, while using the limited production resources in the most efficient way.

If the food system is built up from the most nutrient rich foods first, energy as well as other macro-nutrients will naturally be met, as these are inherent in food groups. For example, milk also contains fat and protein, as well as the micro-nutrients and trace elements as explained above. Therefore, improvement and optimisation of food systems should place priority on nutrient rich foods.


Glossary

Photo by Louis Hansel @shotsoflouis on Unsplash

Food choice varies by individual context


The philosophy of the Sustainable Nutrition Initiative (SNI) is to help create a better understanding of our food systems and identify opportunities for optimisation and improvement. This is to ensure that in the future we can sustainably feed the global population. SNI has developed a modelling approach to test any range of possible scenarios that could contribute to globally sustainable future food systems; The DELTA Model. This Model is unique because it explores the ability of different food production scenarios to provide the bioavailable nutrients needed to adequately feed the global population. It does not try to provide the answer to the perfect sustainable diet for individuals. Rather, it uses scenario testing to generate informed discussion about possible future food production systems.

The options available to feed the world are not the same as the options available to feed individuals. Individuals, particularly those that can afford to, have a lot more choice in their foods and diets, including fortified foods and supplements to ensure their nutrient requirements are met. However, the world’s poorest already spend a large percentage of their income on food and have limited ability to spend more on food. This problem intensifies if food becomes more expensive as a result of changes in global production. Therefore, any recommended changes to food production systems need to ensure that the food they produce is affordable on a global basis. Furthermore, certain diets are not practical at a global level as they would require significant and costly changes to food production and distribution systems. The focus of improving and optimising food systems should be on how the world’s total food production can feed the world’s total population, not dictating an individual diet.

Some individuals have flexibility in their choice of diet

The primary focus of any sustainable food system is to meet nutrient requirements of the population. Looking on an individual scale, all nutrient requirements including macro-nutrients, essential amino acids, and micro-nutrients and trace elements must be satisfied to ensure health and wellbeing. An individual with the wealth and means is likely to be able to meet such requirements on any given diet. Those that can afford it can select a range of nutritious foods and take supplementation and fortified foods where required.

One example is a vegan diet. By omitting meat and dairy, it can be harder to reach the required intake of bioavailable essential amino acids and micro-nutrients, such as such as calcium, iron, zinc and vitamin B12. This is because such nutrients are best sourced from animal-based food groups. However, it is possible to meet nutrition requirements through plant-based foods only with the addition of processed fortified foods and/or supplements to provide the essential micro-nutrients that plant-based foods are often poor sources of. An individual with the wealth and means can consume a variety of nutrient-rich plant-based foods to meet the majority of their nutritional requirements. For example, nuts are high in protein, and pulses contain vitamins and minerals such as folate, iron and zinc. Individuals must also ensure they are consuming a variety of protein sources to ensure they meet their requirements for all essential amino acids, particularly lysine which is often the most limiting amino acid. Most plant-based foods are not complete sources of all essential amino acids. However, if a variety of sources are consumed as part of a meal, requirements can be satisfied.

Not all diets are affordable by everyone

However, some of these choices are only affordable and accessible to wealthier individuals in some parts of the world. The world’s poor spend a much higher proportion of their income on food. The lowest expenditure quintile of the population in Ghana for example, spend over 70% of their household budget on food. Within the US, the lowest income quintile spends approximately 35% of their income on food, while the highest quintile spends only 8% (figure 1). Those that are wealthy have greater flexibility to change their expenditure on food and supplementation as required to fit their chosen diet and lifestyle. Unfortunately, not everyone has this opportunity.

Food spending as a share of income declines as income rises
Figure 1: Food spending and share of disposable income spent on food across US households, 2018

Changes in global food production can make food even more expensive. For example, a significant increase in production of pulses and nuts to meet a global vegan diet would require increases in prices to incentivise suppliers to move away from production of other profitable crops or livestock. Supply of some products may not be able to react quick enough to meet demand, for example tree nuts can take 3 to 10 years before the trees start producing nuts. This will further drive up prices.

However, as prices increase, food unaffordability on a global scale will increase. Research that reviewed 1600 US-based studies on food price elasticity found the value of mean price elasticity to be about -0.60 for cereals and vegetables. This means if the price of cereals and vegetables were to increase by 25%, demand would decrease by approximately 15% globally. These drops in demand would be greater for lower-income households compared to higher-income households, as food is more likely to become unaffordable as prices increase. As a result, the poor, who already struggle to consume adequate nutrients, will be able to afford even less. Even more modest increases in price will render many households unable to afford the food they need.

Changes in diets on a global scale have impracticalities in terms of cost and time required to make the change

Making changes to diets on a global scale may require significant changes to the global food systems in terms of the size of the change and time required, and therefore may not be practical. For example, the world adopting a solely vegan diet as mentioned above, would require land and resources to be converted from livestock to crop production. Production of nutrient-rich plant-based foods such as nuts and legumes would need to be significantly increased. It is one thing to change attitudes, but physical changes to the food systems can be much more difficult. Physical resources would need to be re-allocated, bearing a large cost and requiring a significant amount of time. Cutting animal production would also affect the one billion people who rely on livestock for food and livelihoods.

The focus of improving and optimising the food system should be on the world feeding the world, not dictating an individual diet

Freedom of choice about food can work at an individual level where people have the wealth and means to select the food they want. However, there is no ‘one size fits all’ when it comes to what the world should eat. Diets will vary based on economic and social factors such as income, culture, religion, geographical location and so forth. Moving the entire world to a given diet can result in many being unable to afford nutrition, or costly and time-consuming changes to food systems. Instead, the focus of improving and optimising the food system should be on how the world can feed the world. The scenario-based approach that the DELTA Model allows users to analyse different possibilities of how the world’s total food production can feed the world’s total population. It does not dictate an individual diet, rather it focuses on improvement and optimisation of future food systems. 


Glossary

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An optimal food system is a practical one


The philosophy of the Sustainable Nutrition Initiative (SNI) is to help create a better understanding of our food systems and identify opportunities for optimisation and improvement. This is to ensure that in the future we can sustainably feed the global population. SNI has developed a modelling approach to test any range of possible scenarios that could contribute to globally sustainable future food systems; The DELTA Model. This model is unique because it explores the ability of different food production scenarios to provide the bioavailable nutrients needed to adequately feed the global population. It does not try to provide the answer to the perfect sustainable diet for individuals. Rather, it uses scenario testing to generate informed discussion about possible future food production systems.

A possible food system is one which provides sufficient nutrition to nourish the global population. Once a possible food system is identified, the practicality of implementing this must be considered in terms of the level of change required, the feasibility of the changes, and more importantly, the time taken to implement the required changes. Once possibility and practicality are considered, the food system can be optimised based on other environmental and socioeconomic factors. There is not necessarily one correct answer for what the optimal food systems are. However, it is important to think about the food system in the right way. A thinking failure today will lead to a system failure in the future.

A sustainable food system must deliver the bioavailable nutrients required to nourish the global population.

A possible food production scenario is one which provides sufficient nutrition to feed the global population. Nutrition must come first in any discussion of a food system. Therefore, only food systems that can adequately nourish the world can be considered as sustainable. Not only must the food system have sufficient energy (calories) to feed the world, it also must deliver sufficient fat, protein and carbohydrates (the macro-nutrients), sufficient essential amino acids as part of overall protein, and the required micro-nutrients and trace elements. Further to this, it must account for nutrient bioavailability – the proportion of a consumed nutrients that are actually utilised by the human body.

Based on these criteria, there are likely to be limited choices in what can be considered as “sustainable food systems”. The DELTA model allows users to test diverse scenarios and identify those that could contribute to sustainable global nutrition. The model uses food production information to predict the nutrition available to the average global citizen and compares this against requirements. Where a certain scenario meets requirements, it can be considered as possible.

It is worth noting that individuals are not limited in their choice to the same extent as the world is. Individuals, particularly those that can afford to, have a lot more choice in their foods and diets, including fortified foods and supplements to ensure their nutrient requirements are met. However, what might work for one individual does not necessarily work on a global level.

Not all possible food production scenarios are practical

Once possible food systems are identified, the practicality of implementing the system must be considered. A practical food system is one which has the ability to change and accommodate consequences over a quick enough time period to create a sustainable food system needed by future populations.

Any modification of the food production system will require changes in resource allocation and utilisation, food prices, consumption habits etc. The food system is very complex with multiple inputs, outputs and feedback loops. Planet earth’s resources are limited and are presently allocated for the food that is currently produced and consumed. One billion people currently rely on livestock for their livelihoods. Therefore, any material changes to the types and quantities of food produced will bear significant costs. It is one thing to change global attitudes but making changes in physical resources can be much more difficult. Some scenarios may simply not be feasible due to limited resources such as land.

It is critical to consider the time required to implement such changes. The world is looking to deliver the Sustainable Development Goals by 2030. It is important to be well on the path towards creating a sustainable food system by then. More importantly, while making any changes to feed future generations, current generations must still have access to affordable nutrition. In other words, we cannot put the food system “on hold” while re-inventing it.  If a food system cannot be implemented and make all the necessary changes quickly enough to meet the needs of future generations, then it cannot be considered practical.

Practicality in terms of affordability must be considered

As part of changes required, affordability must be considered. Changes in a food production system can impact the affordability of food. For example, if a proposed food system is higher in more expensive sources of nutrition then it may not be affordable for all. The EAT-Lancet reference diet suggests a diet that is healthy for people and for the planet. However, a recent study found this diet is unaffordable for 1.6 billion people. Moving to more expensive diets may mean a food system is not practical as many cannot afford to get the nutrition they require.

Further to this, as production levels of food groups change, food can become more expensive. Producers require a substantial increase in price to incentivise them to increase production, particularly if this means moving away from production of other profitable products. Supply of some products may also not be able to react quick enough, for example tree nuts can take 3 to 10 years before the trees start producing nuts. This will further drive up prices.

However, if prices increase, demand will start to drop off. Food will become unaffordable to many, particularly those already struggling to buy adequate, high-quality nutrition. A study found the value of mean price elasticity globally to be -0.60 for cereals and -0.58 for vegetables. This means if the price of cereals and vegetables were to increase by 25%, demand would decrease by approximately 15% globally. Lower income countries will experience greater decreases in demand, as food is more likely to become unaffordable as prices increase. Therefore, these regions which already struggle with meeting their nutrition requirements will be able to afford even less. As a result, the global population would not be sufficiently nourished, and that food system could not be considered practical. Practical food systems must be affordable.

The optimal food system must therefore be a practical one

Once possible and practical food systems are identified, they should be optimised based on other environmental and socioeconomic factors, such as greenhouse gas emissions, water utilisation and quality, economic growth etc. A food system that is possible and practical may have unacceptable environmental or socioeconomic consequences. This food system therefore cannot be considered optimal, or these consequences must become a focus for improvement.

There are no clear solutions as to what the optimal food systems are. However, what is important is that optimal food systems must be practical in terms of the changes required to implement them. And to be practical, it must be possible to provide sufficient nutrients to meet global requirements. Any discussion of an optimal food system needs to be constrained by what is practical or it becomes a utopian dream. The right thinking is essential, as a thinking failure today will lead to a system failure in the future. The scenario-based approach that DELTA Model takes enables the informed discussion and planning that is needed to avoid future failure.


Glossary

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The future food system must provide adequate nutrition to sustainably feed the global population


The philosophy of the Sustainable Nutrition Initiative (SNI) is to help create a better understanding of the food system and identify opportunities for improvement in order to sustainably feed the global population with the nutrients required. SNI has developed a modelling approach to test various scenarios for a globally sustainable future food system; The DELTA Model. This model is unique because it explores the ability of different food production scenarios to provide the bioavailable nutrients needed to adequately feed the global population. It does not try to provide the answer to the perfect sustainable diet for individuals. Rather, it aims to generate informed discussion about possible scenarios for future food production systems. This is critical, as a thinking failure today will lead to a system failure tomorrow. 

The fundamental principle of the DELTA Model is that for the global food system to be considered sustainable, it must deliver sufficient bioavailable nutrients to meet the nutritional needs of the global population. Having established the scenarios that can deliver this nutrition, it is essential to examine the associated environmental and socioeconomic consequences. Under such scenarios if the consequences are not acceptable, then a particular scenario is invalid and/or the performance of the environmental or socioeconomic outcomes need to be the focus for improvement.  However, a food system that optimises environmental and socioeconomic outcomes but fails to deliver the nutrition required is not sustainable. In this sense nutrition should come first in assessing future food production scenarios.

For the global food system to be considered sustainable it must deliver sufficient nutrients to meet the needs of the global population. 

According to FAO, a sustainable food system is defined as “a food system that delivers food security and nutrition for all in such a way that the economic, social and environmental bases to generate food security and nutrition for future generations are not compromised. This means that:

  • It is profitable throughout (economic sustainability)
  • It has broad-based benefits for society (social sustainability)
  • It has positive or neutral impact on the natural environment (environmental sustainability)”

The beginning of the above definition is that food security and nutrition is met for all. This means that the food system must produce sufficient nutrients to meet global requirements. While it is essential to examine environmental and socioeconomic consequences, individuals should not be forced to starve or have nutrient deficiencies in efforts to protect the environment. There is no point in ensuring nutrition for future generations if the current generation cannot be sufficiently nourished. This is the basis for the initial phases of building the DELTA model. The Model starts with assessing nutritional needs and the ability of various food production systems to deliver to that nutritional need. 

Nutrition refers to supplying sufficient calories, macro-nutrients, micro-nutrients and trace elements

Individuals must consume sufficient calories and macro-nutrients – fat, carbohydrates and protein – to keep healthy. Protein consumed by the body supplies the  indispensable (essential) amino acids, which are the 9 amino acids that cannot be synthesised by the human body. These amino acids are required to manufacture proteins needed for bodily functions, such as building muscle, transporting nutrients and fighting infection. Essential amino acid deficiencies can result in a range of health issues including decreased immunity, digestive problems, lower mental alertness or slowed growth in children. Therefore, it is important to consider bioavailable essential amino acid supply and not simply protein when assessing a global sustainable diet. 

Equally as important to address are micro-nutrients and trace elements; the vitamins and minerals that are vital for human function. These are all too often overlooked to focus on energy, carbohydrates, protein and fat (the macro-nutrients). Micro-nutrient deficiencies, known as ‘hidden hunger’, are common contributors to poor growth, intellectual impairments, perinatal complications and increased risk of morbidity and mortality. Long term consequences occur not only at the individual level but have detrimental impacts on national economic development and human capital. A sustainable diet must deliver sufficient micro-nutrients to meet global requirements.

Many other models and recommendations of a sustainable diet compare nutrient composition against a generic adult recommended daily intake (RDI). However, this is inaccurate because RDIs vary depending on age, gender and a multitude of other factors. For example, according to New Zealand guidelines, females aged 19-50 require 18mg of iron per day due to loss through menstruation, while their male counterparts require only 8mg. Pregnant women require even more, with an RDI of 27mg/day. Since the DELTA Model takes a global view of the world feeding the world, the daily requirement per person per day is a weighted average based on the expected age and gender range of the population. It does not inappropriately apply the adult RDI for all individuals of the population.

Nutrient bioavailability must be considered

It is not enough to compare nutrient composition directly against requirements, the comparison must also take the bioavailability of individual nutrients in foods into account. Bioavailability refers to the proportion of a consumed nutrient that is absorbed into the bloodstream and used for normal body functions. Not all nutrients can be used to the same extent, depending on various internal and external factors. For example, haem iron, found only in meat, is more readily absorbed by the body compared to non-haem iron often found in plant foods. Haem iron also helps with the uptake of non-haem iron. According to Scientific American, only 1.4% of the iron in spinach can be taken into the body, while 20% of iron from red meat can be absorbed. On a composition basis, spinach has a higher iron content than beef; with 2.7mg/100g vs 1.9mg/100g. However once bioavailability is accounted for, to get the same amount of iron as in 100g of beef, 1.04kg of spinach needs to be consumed.

In addition, protein quality is not equal in different foods. Foods differ in their indispensable amino acid composition, and the bioavailability of these amino acids is affected by a range of food factors. Hence, it is not as simple as multiplying protein content by a single bioavailability factor. Digestible Indispensable Amino Acid Score (DIAAS) is a method to measure protein quality. It measures the true ileal digestibility of individual indispensable amino acids. A score of 1 or greater is considered a complete source of protein, while a score of less than 1 indicates the food is limiting in one or more indispensable amino acid. Using DIAAS, the score for wheat is 0.45, for oats 0.67, for peas 0.65, for soy protein isolate 0.84 and for cow’s milk 1.16. It is therefore vital to take protein quality into account, rather than simply comparing protein composition.

Other models and recommendations of a sustainable diet make the over-simplification that all foods are equal in bioavailability. The DELTA Model is an improvement against such models, because it adjusts for bioavailability when comparing nutrient supply against requirements.

The food system must be built from nutrient rich and bioavailable foods

In order to produce sufficient food to meet global requirements within global resource constraints, it is important to start with foods rich in bioavailable nutrients. Foods that deliver high bioavailable quantities of any nutrient in short supply, as part of an overall nutrient-rich profile are essential to ensure food systems will provide adequate nutrition for the global population. For most food production system scenarios that can be tested with the DELTA Model, it is often not the macro-nutrients that limit the provision of adequate nutrition.  Rather, it is the micro-nutrients and trace elements.  The limitations are most common where the greatest variance in bioavailability occurs. Foods rich in bioavailable nutrients are therefore required. For example, the richest and best-absorbed source of calcium is milk products, which is also rich in other nutrients such as high-quality protein and vitamins such as B12. On the other hand, the best sources of other nutrients, for example vitamin C are plants. This is why a balanced food system with nutrient-rich animal and plant foods is important.

Diets cannot work on a global scale if there are insufficient nutrient-rich foods. For example, suggested diets recomended by EAT-Lancet and Greenpeace suggest a reduction in animal products. While such reductions claim to be good for the planet, they do not necessarily guarantee global nourishment, particularly when it comes to micro-nutrients and trace elements like calcium, vitamin B12, zinc, iron and others. Nutritionist Zoe Harcombe found the EAT-Lancet diet is deficient in multiple nutrients, for example the diet provides only 55% of recommended calcium and 88% of the recommended iron. This is consistent with the DELTA Model, which also indicates it is not possible to meet global nutrient requirements with only plant-based sources of nutrition without supplementation and fortification, which may not be a practical or affordable solution on a global scale.

This does not mean the answer to the global food system is an abundance of animal foods. The current food system is plant dominant; in fact 85% of all biomass that leaves the world’s farms is plant-based. The key is that a food system must be optimised with nutrient-rich foods to ensure global nutrient requirements are met. In other words, the food system is, and should be, plant-based and animal optimised.

The options available to feed the world are not the same as options available to feed individuals, particularly those that can afford to, have a lot more choice in their foods and diets. This includes the consumption of fortified plant-based foods and supplements to meet their nutrient requirements. What might work for one individual does not necessarily work on a global level. The SNI has developed the DELTA Model to generate informed discussion about the possibilities of how the world can feed the world, not to dictate an individual’s diet. And for the world to feed the world, nutrient-rich foods are required.

Once we have established how the world can be nourished, other aspects of the food system must be considered

Once possible scenarios of how the world can be nourished are established, practicality of the food system and improvements required to deliver optimal outcomes must be considered. A solution that can nourish the average global citizen may not necessarily be a viable solution. Wider socioeconomic and environmental factors must be evaluated, such as land and its use, greenhouse gas emissions, water availability and quality, social and economic viability, and so forth. Under such scenarios if consequences are not acceptable, then a particular scenario is invalid and/or the performance of the environmental or socioeconomic outcomes need to be the focus for improvement. However, the DELTA Model puts nutrition first when assessing sustainable food production systems. Any food production systems that cannot adequately contribute to nourishing the world will likely be a sub-optimal use of the world’s scarce and valuable resources.


Glossary

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