The British Nutrition Foudation has published a review paper titled Healthier and more sustainable diets: what changes are needed in high-income countries? It examines the current evidence on the changes required in high-income countries to make diets simultaneously more environmentally sustainable as well as healthier, and identifies research gaps and opportunities.

Agriculture is a major contributor to global environmental change and there is rapidly growing recognition of the need to transform food systems to protect both human and planetary health.

The new British Nutrition Foundation review shines a spotlight on studies that have focused on the dietary changes needed to improve health outcomes and reduce the environmental impact of food production and consumption, and highlights that nutritional quality of diets should be central to the discussion.

What makes diets healthy and sustainable?

Research shows that following government-backed healthy eating advice, such as the UKs Eatwell Guide, across the population can deliver environmental benefits as well as benefitting health, but currently less than 1% of people are achieving all of the Eatwell Guide recommendations. A UK study found that following the Eatwell Guides recommendations more closely would lower the greenhouse gas emissions (GHGE) of current adult diets by 30%, and reduce water use by 4%, as well as reducing mortality risk by up to 7%.

While vegetarian and vegan diets can deliver environmental benefits in terms of GHGE and land use associated with food production, the review highlights that they are unlikely to be widely adopted based on current adherence rates and may reduce intakes and/or bioavailability of some essential nutrients found in foods such as meat, fish, milk and eggs, for example iron, zinc, calcium, iodine, and vitamin B12.

Professor Judy Buttriss, director general of the British Nutrition Foundation and co-author of the review said, "Looking at the available evidence we recommend that an obvious step is to work together with others in the field of nutrition and beyond to promote diets aligned with the UKs Eatwell Guide. An advantage of this kind of plant-rich diet, which can still include some meat, fish, dairy products and eggs, is that it is based on dietary patterns already familiar in the UK and already being adopted to some extent by many of us. However, currently less than 1% of people are achieving all of the Eatwell Guide recommendations, and so there is room for improvement for almost all of us."

Which foods should we eat more or less of?

The Eatwell Guide describes a diet that is rich in foods from plants but can also include some meat, dairy, fish and eggs. A consistent finding of the review is that achieving diets that are both healthier and more sustainable requires a shift in the food choices we make to include more plant-derived foods including vegetables, fruit, wholegrains, beans and other pulses, nuts and seeds, and plant-based meat alternatives that provide essential nutrients and are lower in salt and saturated fat.

Healthy eating advice already acknowledges the need to moderate consumption of red and processed meat and this was also a consistent finding in the studies we reviewed. However, evidence did not suggest the need to cut out meat or other animal-derived foods entirely in order to achieve a healthier and more sustainable diet. In the UK, intake of red and processed meat across the population has been falling and is already at an average of 56g per day amongst adults aged 19-64, within the limit suggested for health (less than 70 g/day on average across the week). However, around a third of people are still eating more red meat than recommended.

As highlighted in the recent National Food Strategy recommendations from Henry Dimbleby, if everyone in the UK complied with the current advice, this would reduce consumption of red and processed meat overall by about a quarter.

Although it is sometimes assumed that the eat less message applies equally to all animal-derived foods, the evidence reviewed in the British Nutrition Foundation paper did not consistently suggest the need to reduce consumption of milk and yogurt or eggs, possibly reflecting trade-offs between the high nutrient density of these foods relative to their more intermediate environmental impact.

Decisions about appropriate substitutes for animal-sourced foods all too often just focus on total protein, but the review emphasises that this is not enough. Increasing the variety of protein-containing foods we choose to eat, including more plant-derived proteins, is part of having a healthier, more sustainable diet. However, most people already eat more than enough protein, and therefore we should consider the overall nutrient profile of foods, says the BNF. As well as protein we also need to consider delivery of the many other essential nutrients that animal-sourced foods provide, if we are to ensure that peoples nutrient intakes do not suffer as dietary patterns shift.

Animal-sourced products currently provide over a quarter of iron, a third of vitamin A and about half the calcium, zinc, iodine and riboflavin in UK adult diets. Therefore, there needs to be careful consideration of how people will consume enough of these essential nutrients in a form that can be easily absorbed by the body if reducing their intakes of animal-derived foods.

Professor Buttriss continued:"While the evidence-base on sustainable food systems has grown significantly in recent years, all too often nutritional quality and delivery of essential nutrients is not considered in judgements about the environmental impact of foods and diets. Its vital that nutrition is central in discussions about transformation of food systems so that we dont risk encouraging dietary changes that might benefit the environment but could be detrimental to peoples health."

How to make diets healthier and more sustainable

While there is no ideal one-size-fits-all solution, there are some actions that everyone can take now that are likely to benefit both their own health and the environment, says the BNF:

1.        Follow the Eatwell Guide which shows the proportions of foods from the main food groups needed to achieve a varied and healthy diet. As well as reducing the environmental impact of diets in the UK on average by about a third, this style of diet will likely improve the health of the UK population by reducing the number of new cases of heart disease, stroke, cancer and type 2 diabetes, and helping ensure nutrient needs to support growth and wellbeing are met for all age groups.

2.        Eat more fruit and vegetables. Fruit and vegetables are a good source of important vitamins, minerals and fibre. Eating at least five portions (80g each) every day of a variety of fruit and vegetables can help to reduce the risk of heart disease, stroke and some types of cancer later in life. Fruit and vegetables also tend to have a lower environmental impact in terms of GHGE and land use than some other types of food.

3.        Diversify and shift the balance of protein intake towards more plant-based sources of protein. Animal foods provide high-quality protein and essential vitamins and minerals, such as calcium, iron, zinc, iodine and vitamin B12 often in a form that is easier to absorb and use. However, we should also aim to expand our choice of protein-containing foods to include more plant-derived sources, such as beans and other pulses, nuts, seeds, and plant-based meat alternatives, for example those based on pulses such as soya or on mycoprotein, provided they are not high in saturated fat or salt. Traffic light labels on the front of packs are a handy way to check the saturated fat, salt and sugar content – go for more greens and ambers and fewer reds. Ready-prepared plant-based foods have attracted a health halo that is not always deserved. Some plant-based alternatives may not contain important vitamins and minerals found in animal-based equivalent products (such as the calcium and iodine provided by cows milk), so also check the label to see if the alternatives have been fortified.

4.        Limit foods high in fat, salt or sugar. As well as being less healthy choices, foods such as cakes, biscuits, pies and pastries also contribute to GHGE associated with our diets, and other impacts on the environment such as water use. Limiting these foods in line with healthy eating guidance can reduce the environmental footprint of diets, especially if such foods are typically consumed in large amounts.

5.        Choose sustainable sources of fish and seafood. Fish is a good source of protein, vitamins and minerals, and oily fish such as salmon, sardines and mackerel also contain omega-3 fats that are beneficial for heart health. Government advice in the UK is to eat at least two portions (140 g each) of fish per week, one of which should be an oily fish. Currently, one third of global fish stocks are overfished, so choose those labelled as sustainably sourced (e.g. the blue Marine Stewardship Council (MSC) label) and check the Good Fish Guide for more sustainable options.

6.        Waste less food. According to the Food and Agriculture Organisation (FAO) of the United Nations, around a third of the food that we produce globally is either lost in the supply chain or wasted by consumers. It has been estimated that food losses and waste contribute as much as 10% of all GHGE globally, but in the UK less than a third of people make a clear link between wasting food and climate change. Wasting less food at home, for example by checking date labels, storing food correctly, or finding creative ways to use leftover food, can all help the environment and save money at the same time – an obvious win-win.