How palatable is the EAT-Lancet report on healthy diets and food systems?
Geraldine McNeill, Visiting Professor of Global Nutrition and Health
Radical transformation of the global food system is certainly needed, but these recommendations generate as many questions as answers.
The EAT-Lancet commission recently outlined a diet which is designed to be compatible not only with improved human health but also with six ‘planetary boundaries’, assuming a global population of 9.2 billion in 2050. The report describes a ‘Healthy Reference Diet’ which could reduce premature deaths from conditions such as cardiovascular disease, type 2 diabetes and common cancers by around 20% while keeping the environmental impact of agricultural production within the planetary boundaries. The diet is not completely vegan but is predominantly plant-based, with a third of the estimated 2500 calories a day provided by wholegrains. Other major components are an average of 300g vegetables, 200g fruit, 125g legumes or nuts, 50g potatoes or starchy vegetables and 250ml milk per day, with only 100g of red meat, 200g poultry, 200g fish and 1-2 eggs each week. Compared to current global patterns of consumption this would require substantial reduction in the consumption of meat in the Americas, Europe and East Asia and of potatoes and starchy vegetables in Africa, Latin America and Europe, and more than doubling of the intake of wholegrains, legumes and nuts in all global regions:
The report presents the Healthy Reference Diet as the definitive road-map for our food system but may not satisfy anyone trying to implement the recommendations or adapt the diet locally. Though there is a broad consensus that for healthy adults in high income countries eating more wholegrains, vegetables and fruits and avoiding high intakes of red meat and processed foods would be beneficial for both health and the environment, there are some aspects of diet in which the trade-offs may be more finely balanced and could vary between populations. Most of the existing evidence on the influence of diet on health is derived from long term follow-up studies carried out in adults in the USA and Europe. As there is an ever-present possibility of bias from this kind of study, evidence from other regions and in other age groups needs to be sought and incorporated in future. The report does mention studies which are at odds with its emphasis on reducing red meat and limiting milk consumption, demonstrating that there are still some inconsistencies in the evidence at present: systematic review methodology such as that used to summarise knowledge on the role of diet in cancer would increase confidence in the health impact estimates and highlight gaps in the evidence.
To select the amounts of each food group in the Healthy Reference Diet the 37 authors used two different methods: comparison of the nutrient content of the proposed diet with estimated nutrient requirements and estimation of the improvement in adult mortality from non-communicable diseases from switching from current diets to the proposed diet in different global regions. Unfortunately data on food composition and estimates of nutrient requirements are lacking or out-of-date for many lower income countries – the international recommendations for vitamins and minerals used were published in 1973 - so mainly US figures were used. While this is unavoidable, details of the values used and the nutrient content of the proposed diets would have helped others to assess the importance of different food groups in achieving the recommendations and the likely impact of variations in food varieties and amounts within the broad recommendations.
Two recent reviews (in Advances in Nutrition and Public Health Nutrition ) have argued that modelling techniques are the method of choice for optimising diet design while balancing trade-offs such as health, environment and cost: this approach would help to answer some of the many practical questions which will arise on application of the EAT-Lancet diet. A shift away from potatoes in Ireland, refined flour pasta in Italy and white rice in Asia will require dramatic dietary change: could similar nutritional and environmental benefits be achieved without such a switch? Can the potential need for dietary supplements of iron and vitamin B12 mentioned in the report be reduced by including organ meat? Is it necessary to restrict consumption of potatoes and starchy vegetables on the grounds of their high glycaemic index in the context of such a high fibre, low refined carbohydrate diet? Are there certain crops, such as soy beans, which could make a greater contribution to environmental and nutritional benefits than e.g. tree nuts? What impact would changing production methods, such as grazing livestock or intercropping legumes with cereals, have on the report’s conclusions?
As it can be hard to picture our meals in terms of quantities of food groups, the EAT website provides seven illustrative meals for 4, along with a weekly shopping list which includes 33 different fruits and vegetables, 16 spices and condiments and 30 other items. These and a UK food writer's suggested food and meal plan vividly highlight the changes in consumer shopping, cooking and eating patterns which would be needed for people to make such an unprecedented shift in dietary behaviour. An ability and desire to buy and cook fresh foods runs counter to the increasing use of out-of-home catering and processed food consumption in many countries, particularly among young people and those living on a tight food budget with limited time and equipment for cooking. It is important that the Healthy Reference Diet is not seen as a luxury for those who enjoy food preparation and can afford a varied diet but can be achieved by all those with limited food budgets everywhere.
The report concludes that five main actions are needed to achieve the ‘Great Food Transformation’: international and national commitment to shifting towards healthy diets; re-orientation of agricultural priorities to producing healthy foods; sustainable intensification of food production; strong and coordinated governance of land and oceans and at least halving of food losses and waste. These echo other calls to action which are clear on the directions of travel needed but less clear on how such radical changes can be achieved. Inclusion of the perspectives of the farmers, food processors and retailers who will be required to implement such changes is needed, along with support for producers whose livelihoods are likely to be adversely affected. But probably the greatest challenge will be to convince consumers to change their dietary preferences to wholegrains, legumes, nuts and vegetables and away from animal products and the low-cost fast foods which have increasing global penetrance and universal appeal. Food for thought, indeed.