The United Nations proposed Sustainable Development Goals include ending hunger, improved nutrition and sustainable agriculture (Goal 2), healthy lives and well-being (Goal 3) and sustainable consumption and production patterns (Goal 12). To achieve these goals we need to move towards a diet that is adequate, healthy and sustainable for all.
Many public health organisations emphasise a healthy balanced diet consisting of at least two-thirds fruit, vegetables and whole grain cereal products, with smaller amounts of meat, fish and dairy. This model has also been adopted to create a more sustainable dietary pattern (see for example the New Nordic Diet , and the Double Pyramid and the Dietary Guidelines for the Brazilian population. It is well established that consumption of meat and animal products use proportionally more resources than plant foods in both land and energy and generate more greenhouse gases . Therefore to realise the sustainable development goals that address diet, plant-based diets should be emphasised as a healthier more sustainable option.
Lessons from the UK on diet and sustainability
A move towards a more plant-based diet (i.e. fruit and vegetables, wholegrain cereal products with minimal processing) would be good for population health and the environment. A plant-based diet is likely to be lower in calories  which should alleviate the obesity epidemic as well as prevent chronic diseases such as cancer. Researchers in Scotland have shown that the ‘Livewell Diet’ can be achieved which meets the recommendations for health (as displayed for example in the eatwell plate and the UK Dietary Reference Values  ) and results in reducing greenhouse gas emissions by 25%.
The Livewell Diet is characterised by five main sustainable diet principles: waste less food, eat less processed food, eat more plants, eat less meat and buy food that meets a credible certified standard. However, convincing consumers of the need to change their diet is not easy and our work on the Scottish Diet  using UK food purchase survey data, with adjustment for waste showed that there has been little change in the diet over the period 2000-2012.
Make access to fruit and veg-based diets a priority
While eating fruits and vegetables is the basis of a healthy, sustainable diet, the daily average fruit and vegetable consumption has shown no change since 2000 i.e still less than 2.5 portions per day (5 a day recommended). There were similar findings for fibre intake which remained low and only equated to around two-thirds of the recommended daily allowance. Red and processed meat consumption did reduce slightly, but processed meat was around two-thirds of total meat consumption thus adding to energy costs due to processing.
What was apparent from this study is that there are clear socioeconomic differences as those who consume large amounts of meat and sugar, and less fibre, fruit and vegetables tend to be more from deprived groups. However, even for the least deprived fifth of the population the goals for fruit and vegetables, fibre and free sugars were not being met. Using the UK as an example, to meet target 2.1 creating access to diets mainly based on fruit, vegetables and fibre is necessary for ending hunger by 2030 and for 2.2 in ending malnutrition.
Is a healthy diet more sustainable?
We should not assume that a healthy diet will always be more environmentally sustainable. The general public have different ideas as to what constitutes a healthy diet such as the current trend for low carbohydrate (e.g. http://authoritynutrition.com/low-carb-diet-meal-plan-and-menu/) which could reduce the plant contribution to the diet even more. Plant-based diets tend to be higher in carbohydrates and lower in proteins . The environmental impact of diet to date has been restricted to considering the greenhouse gas (GHG) reductions up to the time the food reaches the regional distribution centre (RDG), often termed pre-RDG GHG.
This does not take into account the post RDC GHG of aspects such as refrigeration and transport of fruit and vegetables and the waste generated (25% of avoidable household waste compared with 6% for meat and fish). Broader environmental issues need to be considered such as land use change, use of water resources, seasonality of food production, pollutants and biodiversity , not to mention the actual cost of the diet to the consumer. In addition there is evidence that organically produced food is not necessarily “environmentally superior”- this appears to be the case for poultry, eggs and milk    and is of particular relevance to target 12.2 in achieving “…sustainable management and efficient use of natural resources”.
There are plans for these aspects to be incorporated into further work at Newcastle University in the coming years building on the current Life Cycle Analysis work carried out on eggs, poultry and pork in the School of Agriculture Food and Rural Development   and expertise in dietary assessment and survey methodology in the Human Nutrition Research Centre  .
Reduce dependence on animal-based diets
We need to define healthy and sustainable diets that are culturally and financially acceptable across the globe, especially in meeting targets 12.2-12.5 in reducing food, energy and chemical wastes at all levels of the food production chain. Most of the diets designed to date are for developed nations but what about the developing nations aspiring to a more Western diet and increasing the demand for animal products? There are no targets for reducing dependence on animal-based diets, which is interconnected with achieving less energy intensive and low-carbon economies.
Inequalities in dietary intake occur within countries and health and social inequalities are a contributing factor as well as an outcome. The problem will not be solved by health and agricultural scientists alone, but requires combining expertise from a range of relevant disciplines. We need to also understand the causes of poor dietary intake and work with social scientists to address the economic and cultural reasons for inequalities that will ultimately allow us to achieve Goal 3 to ensure healthy lives and promote well-being for everyone.
Dr Wendy Wrieden is a registered nutritionist based at the Institute of Health & Society and Human Nutrition Research Centre at Newcastle University. She has led numerous research projects concerned with dietary interventions, surveys and dietary assessments including a project to monitor the Scottish diet. email@example.com
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