Tess Warnes, Dietian at food procurement expert allmanhall, explains what a sustainable diet is, and whether it is also a nutritious one.

A sustainable or plant-based diet means a move to a dietary pattern that has a greater emphasis on foods derived from plants, but can include some meat, fish, eggs and dairy. Guidelines to a healthy diet are set out in the Eat Lancet planetary health diet, which recommends a diet that is varied and is the right quantity for the individual to reduce waste as well as obesity or equally malnutrition.

When considering the nutritional implications of a plant-based eating pattern, it is important to grasp what this looks like, and then to understand what, if any, are the relevant nutritional considerations. 

What our current diet looks like

In the most general terms, as a population our current diet is not sustainable or healthy. The most recent UK National Diet and Nutrition Survey (NDNS) data shows that our population’s intakes of saturated fat, sugar and salt are above the Government recommended levels. Whereas intakes of fibre, fruit, vegetables, and oily fish are below Government recommendations. Our current dietary habits are fuelling obesity, type 2 diabetes, heart disease and some cancers.

What does a sustainable diet look like?

In the UK, the Eatwell Guide provides a model for a healthy, varied diet. It is estimated that if everyone in the UK adopted this diet, it would lead to reductions in associated GHGE (45% lower) and land use (49% lower). Following the Eatwell Guide means eating at least 5 portions of fruit and vegetables a day, wholegrain and higher-fibre starchy foods, and diversifying protein intake more towards plant sources. This includes beans and other pulses, as well as plant-based meat alternatives. It also includes nuts if safe to do so, alongside eggs, some dairy foods or alternatives and sustainably sourced fish. This should be done whilst also limiting consumption of foods high in fat, salt, and sugar.

A recent study found increased adherence to the recommendation on reducing red and processed meat consumption was associated with the largest decrease in environmental impacts and carbon footprints. 

This same study found if everyone in the UK consumed a diet in line with these recommendations, it would lead to significantly less type 2 diabetes, coronary heart disease, stroke and cancer.  

What are the specific nutritional considerations of a sustainable diet?

Protein 

Protein is often the nutrient of concern when switching to a more sustainable diet. 

However, current UK protein intakes exceed the recommended daily intake, including those following a vegan diet (The One Blue dot). So reducing meat will not negatively impact protein intake, if replaced with a variety of different plant-based proteins. Beans and lentils are particularly nutritious, often described as power houses for nutrition, high in protein, fibre, micronutrients as well as the bonus of being cheap.

Fibre 

Our current diets are particularly poor when it comes to meeting our fibre requirements. The recommendations for fibre intake are; 30g per day for adults, 20g for 5-11 year olds and 25g for 11-16 year olds. 

There is strong evidence that diets rich in fibre, particularly cereal fibre and wholegrains, are associated with a lower risk of many health conditions, including cardiovascular disease, coronary events, stroke, type 2 diabetes and colorectal cancer. 

Iron 

Iron requirements can be achieved by ensuring plenty of plant-based iron sources such as fortified breakfast cereals (preferably not ultra-processed or high sugar options), nuts, seeds and vegetables. Red meat can be consumed in small amounts, which is particularly relevant if concerned around intake for more vulnerable groups. 

Zinc 

Consuming a small amount of meat will likely achieve zinc requirements. Including more seeds and choosing wholemeal or wheatgerm breads will also contribute to zinc intake as well as including Quorn as a meat alternative, which has a similar content to beef. Vulnerable groups not consuming any red meat may benefit from taking a nutritional supplement. 

Calcium 

Switching some or all of milk to plant-based drinks will have little or no impact on calcium intake due to fortification of these products, however organic products may not be fortified.  

Iodine 

The majority of plant-based drinks are not fortified with iodine. However, although dairy does contribute to iodine intake, if some dairy is still being consumed along with small amounts of other animal foods such as fish, seafood, yogurt and egg, it is likely that adequate iodine intake would be achieved. Plant-based sources include wholemeal bread, lentils, seeds and beans, tofu. Some on a fully vegan diet, however, may need to consider a supplement. 

Vitamin B12

Vitamin B12 is only available from animal sources and a few fortified plant foods. 

For most adults still consuming reduced amounts of meat, dairy, and eggs, achieving recommended amount should not be a challenge. Plant-based sources include fortified breakfast cereals and plant-based milk, and marmite. A vegan diet would need a supplement.

Omega 3 

A sustainable diet includes 2 portions of fish a week, one which should be oily to ensure sufficient omega 3 fatty acids EPA and DHA.  Those not eating fish will need to include nuts and seeds such as walnuts and pumpkin seeds or consider a supplement to meet omega 3 requirements. 

A sustainable diet is a healthy diet.  

All the evidence shows moving to a more plant-based diet will have a positive impact to our health and will meet our nutritional requirements. A sustainable plant-based way of eating doesn’t need to be vegan or vegetarian, and can include small amounts of meat, fish, and diary.