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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