The cheapest nutritionally adequate diet contains both plant- and animal-sourced foods

A recent paper published in Nature Food asked what foods would be in the cheapest diet that satisfies nutritional requirements. Combining the prices and food composition data for common food items in the US, the authors determined the cheapest way to feed one person a nutritionally adequate daily diet.

The cost of the diet was calculated as US$1.98 per day (NZ$3.02). It consisted of 15 foods, all of which could be found in the average US home kitchen. The top five contributors were milk, legumes, rice, potatoes and corn tortillas.

The authors also analysed what level of price increase to animal-sourced foods was necessary before the cheapest diet became entirely plant-based. Between 200-1,150% increases in the cost of animal-sourced foods was required, and the plant only diet would cost US$3.61 per day (NZ$5.51). The plant only diet overlapped with the original diet for many foods, but also included soy beverages, green peas and peanut butter.

The authors highlighted that the bioavailability of consumed nutrients was not considered in this study. Inclusion of bioavailability would likely increase the cost of both diets but would have a greater impact on the plant-based diet, due to the lower bioavailability of many nutrients in plant foods. The daily diets proposed by the authors are not recommended diets – a limit of 15 different foods is not feasible – but the work does show that animal-sourced foods can be a cost-effective way to get adequate nutrition.

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Impact of COVID-19 lockdowns on sustainable nutrition

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Many countries across the world instituted a degree of lockdown this year to minimise the harm caused by the COVID-19 pandemic – but what effect does a lockdown have on nutrition and sustainable food production?

The impact of the Spanish lockdown during March and April 2020 on nutrition has recently been investigated by researchers from multiple Spanish and international universities. They found that the amount of food purchased increased slightly during the lockdown (from 13.8 to 14.3 kg per person per week). Plant foods were the major part of the increase, followed by eggs and red meat. Beer and coffee purchasing decreased, possibly due to the closing of restaurants and bars.

Food energy intake increased by 6% during the lockdown compared to the same period in previous years, while the nutritional quality of the lockdown diet was 5% lower. The environmental footprint of the lockdown diet was also greater than pre-lockdown: increases were found for water use, land use and global warming potential.

While this study only considered the impact of the Spanish lockdown, the trends are likely to be true for lockdowns in many countries. The results of this research highlight that changes to the global food system must take into consideration the potential for unexpected events to disrupt progress towards sustainable nutrition.

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Emissions on farm vs off farm

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The Environmental Working Group breaks down the life cycle analysis of total greenhouse gas emissions for common protein foods and vegetables.

As expected, animal foods have significantly higher greenhouse gas emissions. Lamb, for example, has the highest because it generates methane through enteric fermentation and produces less edible meat relative to the sheep’s live weight. Most emissions from meat, dairy and fish occur during production. However, most emissions from plants are generated after crops leave the farm. This is primarily because of the energy needed to cook plant-based foods. For example, post-farmgate emissions account for 65% of dry beans’ total emissions and 59% of lentils’ total emissions.

This does not mean plant-based foods have greater net post-farmgate emissions. For example, 65% of dry bean’s emissions is post-farmgate, which equates to 1.3kgCO2e. On the other hand, while only 10% of beef’s emissions is post-farmgate, this is a larger total of 2.7kgCO2e. The key message is that the main sources of emissions vary among different foods, depending on production and food preparation methodology. This means it is inappropriate to only compare footprints at the production stage. A more holistic view of environmental impact is required for a fair comparison.

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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.


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Multiple health and environmental impacts of foods

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Researchers at the University of Minnesota and Oxford University compared the environmental effects against the noncommunicable disease risk of certain food products.

It was found that foods associated with improved health outcomes; whole grain cereals, fruits, vegetables, legumes, nuts and olive oil, had amongst the lowest environmental impacts. In contrast, foods associated with the largest negative environmental impacts—unprocessed and processed red meat—were associated with the largest increases in disease risk. Chicken, dairy products, eggs, and refined grains had no significant impacts on either disease risk or environmental metrics. The report concluded that dietary transitions towards greater consumption of healthier foods would generally improve environmental sustainability.

These findings could help consumers, policy makers, and food companies to better understand the multiple health and environmental implications of food choices. However, this study looked at non-communicable disease incidence only, and did not address many other factors, not the least of which are nutrient deficiencies and the impact of nutrition on child development. For example, red meat plays a key role in the contribution to global requirements for multiple micro-nutrients such as iron, zinc and vitamin B12.

In addition, not all research agrees with the findings of this study. The Global Burden of Disease study found that a diet high in red and processed meat had very little impact on the risk of death or disability-adjusted life years. Diets low in healthy foods such as fruits and wholegrains, or high in sodium had a much higher mortality rate. Another study found that advice to eat less red meat is not backed by sufficient scientific evidence.

It is not as simple as eliminating red meat to improve both health and the environment. Many factors must be considered in conjunction when making decisions about the food system, as a thinking failure today will lead to a system failure tomorrow.

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Australia’s changing landscape of protein production

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A study by the Australian Farm Institute tells us that despite the trend towards alternative proteins, large opportunities exist for animal proteins in the future.

The Australian population is growing, forecast to be nearly 29 million by 2030. This will inevitably result in an increased demand for protein. While alternative protein substitution has increased and will continue to do so in the next 10 years, this will not diminish the demand on animal agriculture. Rising demand for protein driven by that population growth will outweigh any additional market share that alternative proteins may gain. However, the current production systems have finite resources. Therefore, both animal and plant production will need to become more efficient and productive if Australia wants to avoid relying solely on food imports to sustain their future population

It is worth noting that the current global food system is plant-based and animal-optimised. Approximately 85% of all biomass leaving the world’s farms is plantsourced. For any sustainable food system to nourish the global population, both animal and plantsourced foods will continue to be required. Animal-sourced foods are particularly important to meet global requirements for micro-nutrients such as iron, zinc and vitamin B12. In fact, scenario testing of possible global food systems with the DELTA model repeatedly demonstrates that animal-sourced food production will not only continue to be needed to provide adequate nutrition to a global population, but that production will also need to be sustainably increased.

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‘Meat is part of a sustainable world’: Professor Louise Fresco

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Professor Louise Fresco (President of the Executive Board, Wageningen University & Research) argues that taking meat out of the food system is not the solution.

The future of the world will be characterized by eating less meat as we shift towards flexitarian and reductionist diets. However, meat should remain as part of a sustainable food system. Fresco highlights the valid point that grazing animals utilize land that cannot be used for anything else, converting inedible plants into valuable food. Nutrient-rich meat also becomes increasingly important, particularly with the aging population.

This is consistent with results from testing food production scenarios with and without meat for their ability to provide adequate nutrition for the global population, using the DELTA model. Key micro-nutrient requirements such as iron, zinc and vitamin B12 cannot adequately be sourced for the global population without the inclusion of animal-derived foods in the food supply system. In other words, animal-derived foods are necessary to nourish the global population. Meat, as well as dairy, should continue to be a part of our diets. However, effort must be made to ensure it is produced in the most sustainable way. This increases the pressure for research to reduce on-farm emissions, reduce water usage and improve water quality, and increase productivity from animal agriculture.

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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. 


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Study shows the EAT-Lancet diet is unaffordable for at least 1.6 billion people

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A study has found the EAT-Lancet diet is unaffordable to 1.6 billion people, mostly in sub-Saharan Africa and South Asia.

The ‘planetary health diet’ costs a median of USD $2.84 per day, which is about 60% more expensive than a diet that meets our minimum nutritional requirements. The study found that the diet costs between 3% to 73% of national average incomes. Fruit and vegetables and animal-sourced foods are the most expensive components of the EAT-Lancet reference diet.

The EAT-Lancet diet has many flaws, it is not the perfect diet. But it generates good discussion about what needs to be done to make a healthy and sustainable diet affordable for the global population. A cost-effective diet must be optimised on cost per nutrient or bundle of nutrients. The issue with the EAT-Lancet reference diet is that it involves switching from low cost sources of nutrition to more expensive sources to deliver the nutrients we need. Even then, the EAT-Lancet diet falls short on supplying nutrients such as iron and calcium in adequate amounts, and the protein quality of the diet is lower.

Furthermore, switching to more expensive sources of nutrition means supply and demand can get out of balance due to demand increasing from those who can afford those foods. Supply may not be able to react quick enough, for example, tree nuts take 3 to 10 years before the trees start producing nuts. As a result, prices will increase, and food will become even less affordable to some of the population.

To make a sustainable diet affordable by the global population, the cheapest source of quality, bioavailable nutrients should be prioritised. For example, in the US, dairy is the lowest cost source of dietary calcium, riboflavin and vitamin B12, and should therefore be prioritised.

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Reducing agriculture emissions through improved farming practices

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McKinsey’s latest report, Agriculture and climate change offers a perspective on how 25 proven GHG-efficient farming technologies and practices could reduce emissions by about 20% by 2050.

This is equivalent to a combined 4.6 GtCO2eq by 2050 compared with business-as-usual emissions. The top 15 measures cover four key areas; energy, animal protein, crops, and rice cultivation. For example; adopting zero-emissions on-farm machinery and equipment, improving animal health monitoring and illness prevention, employing greenhouse gas-focused genetic selection and breeding, and improving rice paddy water management. The top 15 practices would contribute 85% of the emission reduction potential.

The report addresses the issues with greenhouse gas emissions from agriculture, forestry, and land-use change, and recognises that major changes are needed to reduce emissions. These changes may be more challenging for agriculture than for other sectors. In addition to this, the agriculture sector has a complicated set of objectives to consider including global nutrition need, food security, biodiversity and the livelihood of farming communities. This cannot be ignored in efforts to reduce emissions. It is therefore essential to take these suggested efficient farming actions to reduce greenhouse gas emissions, while still considering the importance of still being able to produce sufficient food to nourish the world with the nutrients they require.

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