The science of a healthier and more sustainable diet

Key points

• Feeding a growing population while reducing current levels of malnutrition, and the environmental impact of our food system, presents a major challenge.
• A healthier a more sustainable diet is one that balances multiple dimensions, including nutrition, health, economic and cultural considerations, alongside a lower environmental impact.
• The Eatwell Guide provides a model for a healthy, balanced diet that may also help achieve reductions in greenhouse gas emissions and land use, as well as small reductions in water use.
• We should aim to diversify and shift the balance of our protein intake towards more plant-derived protein sources, including eating more beans and other pulses (like lentils), nuts, seeds, and plant-based meat alternatives that provide essential nutrients and are not high in salt or saturated fat.
• Evidence suggests that more sustainable dietary patterns are mainly based on plant-derived foods but can include some meat and moderate amounts of dairy foods (ideally lower-fat and lower-sugar versions), while having also having a lower environmental impact.
• Consuming foods high in fat, salt and sugar (such as cakes, biscuits, pies and pastries) less often and in smaller amounts can help improve diet quality and reduce our environmental footprint.
• Choosing fish from more sustainable sources (such as those with the blue MSC logo), and trying less familiar species, can help to protect fish stocks and support sustainable production methods.
• Reducing food waste is an essential component to eating more sustainably, but the link between food waste and climate change may not be recognised by many consumers.

Summary

There is widespread recognition of the need to transform the way in which we produce and consume food if we are to address the current global burden of malnutrition and ill health associated with poor diets, while also reducing the environmental impact associated with food production. At present, the global food system is responsible for over a third of global greenhouse gas emissions (GHGE), almost 40% of land use and 70% of freshwater use. Globally, food systems must be transformed to mitigate these environmental effects, at the same time as ensuring that sufficient quantities of safe, nutritious and affordable food are made available in an equitable way to support a growing population. Meeting this challenge will require engagement of multiple stakeholders, including farmers and producers, businesses, governments, NGOs, and the public.

A healthier and more sustainable dietary pattern is one that balances multiple dimensions, including nutrition, health, economic and cultural domains, alongside a lower environmental impact. While research in this area is ongoing, evidence to date indicates that adopting existing national dietary guidelines in high-income countries (including the UK, Europe and US), has the potential to improve health and reduce environmental impacts.

In the UK, the Eatwell Guide provides a model for a healthy, varied diet. It is estimated that if everyone in the UK adopted a diet in line with the Eatwell Guide, this would lead to reductions in associated GHGE (45% lower) and land use (49% lower), as well as small reductions in water use (4% lower). Following the Eatwell Guide means eating plenty of a variety of fruit and vegetables (at least 5 portions a day), and wholegrain and higher-fibre starchy foods, and diversifying and rebalancing protein intake more towards plant sources (like beans and other pulses, nuts), and plant-based meat alternatives that are lower in salt and saturated fat (like tofu, mycoprotein), alongside some dairy foods (or alternatives), eggs, and sustainably sourced fish. Reducing household food waste is another essential component of eating more sustainably, especially as many consumers may not the impact of food waste on climate change.

Vegetarian and vegan diets can have a low environmental impact but may reduce intakes and/or ‘bioavailability’ (how well a nutrient is absorbed and utilised by the body) for some essential micronutrients (such as calcium and zinc) that are typically provided by animal-derived foods in the current average diet.

While it is generally agreed that meat and dairy products are associated with more GHGE and land use than other types of food, there is substantial global variation in the environmental impact of these foods. Studies suggest that a healthier and more sustainable diet is one mainly based on plant-derived foods, but can include some meat and dairy foods, while also having a lower environmental impact.

The need to change how we produce and consume food

There is widespread recognition that we need to transform our current global food system to improve both human and planetary health. Poor quality diets are responsible for 1 in 5 deaths worldwide, and malnutrition in all its forms (including both under- and over-nutrition) remains a major public health concern. At the same time, food production is considered one of the main drivers of global environmental change (including climate change), although a third of the food produced for human consumption is wasted or lost in the supply chain. We are also faced with the challenge of feeding a growing population. Coupled with rising incomes in developing nations, it is estimated this will require a 50% increase in current levels of food production by 2050 to keep up with demand. The question of how we can continue to produce more food with fewer resources, such as land, water and fuel, while improving human health, is one of the greatest challenges facing humanity in the 21st century and is central to the concept of a diet that is both healthier and more sustainable.

The following sections outline the practical steps that can be taken in high-income countries like the UK to eat in a healthier and more environmentally sustainable way. A PDF document is also available as a download (see the bottom of this page), which provides a more detailed explanation of the science behind how global food systems need to change to support sustainable food production and consumption and improve human health.

How to eat more sustainably

The complexity of the issues surrounding sustainability of the global food system appears to make it almost impossible for us to know, at the point of picking up a food item in the supermarket, what its impact on the planet to date has been. However, there is enough evidence to support some general principles that we can adopt in countries such as the UK to eat more sustainably, as well as healthily.

1. Eat a more plant-rich diet by following the Eatwell Guide

In the UK, the Eatwell Guide is designed to help all those aged over 2 years of age to eat a healthy, balanced diet. The Guide was launched in 2016 by Public Health England, following changes to the previous iteration of the model (the Eatwell Plate) to meet revised recommendations on free sugars and fibre, while minimising the need for significant changes to existing dietary habits (based on data from the National Diet and Nutrition Survey). Find out more about the Eatwell Guide on our page on the science of healthy diets.

The Eatwell Guide recommends a plant-rich dietary pattern, predominantly composed of plant-derived foods, including:

• Plenty of starchy foods (such as bread, potatoes, rice and pasta), preferably wholegrain and higher fibre versions, as well as at least five portions a day of a variety of fruits and vegetables. Together, these should make up just over two-thirds of the food we eat.
• An emphasis on a diverse range of protein-containing foods that is balanced towards more plant-derived options, such as beans and other pulses (like lentils), nuts and seeds (and foods based on these), in place of some animal-derived sources such as lean meat/poultry, alongside some eggs and lower-fat and lower-sugar dairy foods (or alternatives).
• Two portions of ‘sustainably sourced’ fish (140g each) per week, one of which should be an oily fish (such as salmon and mackerel).
• A small amount of unsaturated oils and spreads.
• Limited amounts of foods and drinks high in fat, salt and sugar (including cakes, chocolate, sweets, biscuits, sugars-sweetened drinks, crisps), which are not needed in the diet, and if eaten should be included less often and only in small amounts.

For more information about how to plan meals in order to achieve the Eatwell Guide, including portion sizes read our page 'Get portion wise!'.

Following the Eatwell Guide is likely to have both environmental and health benefits. An analysis performed by The Carbon Trust (and commissioned by Public Health England) in 2016 estimated that consuming a diet in line with the Eatwell Guide would reduce the environmental impact of current average UK diets by 32% (45% lower greenhouse gas emissions, 4% lower water use and 51% lower land use). The reduction was attributed to several factors, including increasing the consumption of potatoes, fish, bread, fruit and vegetables and lower consumption of dairy foods, meat and sweet foods. A cost analysis of the Eatwell Guide concluded that the price of a diet in line with these recommendations (£5.99 per adult per day) would be very similar to the typical diet already consumed at the time by the UK population (£6.02 per adult per day).

More recently, a study comparing the impact of adherence to the nine food and nutrient-based recommendations of the Eatwell Guide (those for fruit and vegetables, oily fish, other fish, red and processed meat, total fibre, total salt, free sugars, saturated fatty acids and total fat) found that those people meeting between 5 and 9 recommendations (intermediate-to-high adherence) had 30% lower dietary GHGE than those meeting between 0 and 2 recommendations (very-low adherence). Higher adherence to Eatwell Guide advice was also associated with a 7% reduction in mortality risk (risk ratio: 0.93; 99% CI: 0.90 to 0.97).

Another earlier analysis (also from 2016) indicated that the associated health benefits of widespread adherence to the Eatwell Guide could be significant. It was estimated that if everyone in the UK consumed a diet in line with these recommendations, this would lead to 780,000 fewer new cases of type 2 diabetes by 2026, as well as significantly fewer new cases of coronary heart disease, stroke and colon cancer (see figure).

2. Eat at least five portions of fruit and vegetables a day

Fruit and vegetables are a good source of important vitamins, minerals and fibre. Eating at least five portions (80g each) of a variety of fruit and vegetables each day can help to reduce the risk of heart disease, stroke and some types of cancer.

Fruit and vegetables also tend to have a lower environmental impact in terms of greenhouse gases and land use than some other types of food. The National Diet and Nutrition Survey (NDNS) indicates that on average only a third of UK adults (33%) currently meet the 5 A DAY recommendation. The proportion of children and adults meeting the recommendation has also not increased significantly during the 11 years of the NDNS rolling programme (between 2008 and 2019; except for women aged 19-64 years). Therefore, finding ways to get more fruit and vegetables into our diets is likely to have health and environmental benefits. However, it is important that efforts to increase fruit and vegetable consumption do not lead to higher levels of food waste, as fresh vegetables and salad are the most highly wasted type of food in UK households, accounting for 28% of edible food waste by weight.

3. Diversify and shift the balance of protein intake towards plant sources

Meat is a good source of protein and provides essential vitamins and minerals, such as iron, zinc and vitamin B12, but it also typically has a higher environmental impact than plant-derived protein foods. It is recommended that individuals consuming on average more than 90g/day of red and processed meat (cooked weight) should cut down to no more than 70g/day, as evidence suggests that a high consumption of red and/or processed meat is linked with an increased risk of bowel cancer.

We should aim to diversify and shift the balance of protein-containing foods we eat towards more plant-derived protein sources, including eating more beans and other pulses, nuts, and seeds, and plant-based meat alternatives (such as soya- or mycoprotein-based alternatives, or tofu) that are lower in saturated fat and salt.

The Eatwell Guide also includes advice to consume two portions of fish per week (one of which should be an oily fish) from sustainably managed sources (see below for more information). Aiming for greater diversity of protein-providing foods in the diet is likely to reduce our environmental footprint and may also increase intake of some important nutrients (such as fibre provided by beans and other pulses).

Evidence shows that more sustainable dietary patterns can include moderate amounts of dairy foods, which typically provide protein and important micronutrients (such as calcium and vitamin B12, iodine) at a lower environmental impact than meat. However, it is recommended to choose lower sugar and lower fat versions of products where possible. If consuming dairy alternatives, such as oat- or soya-based drinks or yogurts, it is recommended to choose unsweetened versions that are fortified with calcium and other important nutrients (such as vitamin B12 and iodine).

4. Limit foods high in fat, salt and sugar

Foods high in fat, salt and sugar (HFSS), such as cakes, biscuits, pies and pastries are not healthy choices, and are not needed within a balanced diet. These foods are typically calorie dense and can make it easier to consume more calories than needed, which can increase the risk of obesity. Currently, most people in the UK are consuming too much saturated fat, salt and sugar, and need to cut down.

Consuming HFSS foods less often and in smaller amounts can also be a good way to reduce our environmental footprint. Studies have shown that when these ‘discretionary’ foods make a large contribution to dietary energy intake, they can also make a substantial contribution to overall dietary GHGE, as well as land and water footprints of diets. Restricting HFSS foods can therefore help achieve both health and environmental objectives.

5. Choose fish and seafood from sustainable sources

UK dietary guidelines recommend that adults eat two 140g portions of fish a week, one of which should be an oily fish (such as salmon, mackerel and sardines). However, fish consumption in the UK is currently fairly low on average (22g per day of total fish and 8g per day of oily fish for adults) – well below the recommended intakes of 40g per day (total fish) and 20g per day (oily fish). Fish is a good source of protein and contains vitamins and minerals not widely found in other foods, such as long chain omega-3 fatty acids (EPA and DHA) found in oily fish, which may be beneficial for heart health, as well as vitamin D, which is important for bone and muscle health.

Worldwide, annual fish consumption per capita more than doubled between 1961 and 2017, reaching 20.5kg per person per year. This increased demand for fish has put pressure on global fish stocks. According to the FAO, 34% of worldwide fish stocks were estimated to be overfished in 2017, a figure which has increased dramatically in recent decades, from only 10% in 1974.

This has raised concerns about the appropriateness of dietary advice to eat more fish. Some types of seafood may also have a particularly high environmental impact. For example, farmed prawns and shrimp have a high average blue water footprint (that drawn from ground or surface water). However, resource use varies considerably between producers globally, by as much as 9.4-fold and 6.6-fold for freshwater withdrawals for farmed fish and crustaceans, respectively, when comparing the 10% of ‘most impactful’ with the 10% of ‘least impactful’ producers. Therefore, encouraging more sustainable production practices is important, especially as aquaculture (the farming of seafood species) now accounts for almost half (46%) of total global seafood production, and has increased dramatically in the last few decades (more than double from 1996-2005 to 2018).

Consumers can help to drive the market for sustainable seafood by choosing fish and seafood from responsibly managed sources, which are caught or farmed in ways which aim to minimise damage to the marine environment (such as line caught). It is also important to select species that have not been overfished, which can be done in the following ways:

• Choose as wide a variety of species as possible: At present, in the UK we are too reliant on 'the big 5’ (cod, haddock, tuna, salmon and prawns), so try experimenting with less familiar species for which stocks are believed to be more abundant, such as mussels, mackerel and European hake. For more information read the Marine Conservation Society Good Fish Guide.
• Look out for ecolabels on certified fish products: The blue Marine Stewardship Council (MSC) logo; the Soil Association (Organic) logo; Aquaculture Stewardship Council (ASC) certification; and RSPCA monitored logos. These are certifications that provide assurance fish has come from a well-managed and sustainable source. This includes standards for how stocks of wild and farmed seafood are managed (such as only fishing in areas with healthy stocks), as well as requirements for animal welfare (such as water quality and stocking density).

6. Reduce household food waste

The FAO has estimated that around a third of the food that we produce globally is either lost in the supply chain or wasted by consumers. Food waste is a major contributor to climate change and accounts for as much as 10% of total anthropogenic GHGE (those due to human activity), according to the IPCC (Intergovernmental Panel on Climate Change). Reducing the amount of food that we waste is a key part of making our diets more sustainable, and is included in the UN Sustainable Development Goals, which have set a target to halve global per capita food losses and waste by 2030 (Target 12.3).   

In the UK, the amount of food wasted has fallen by 7% in recent years (between 2015 and 2018), which is enough food to fill the Royal Albert Hall ten times over. It is also estimated this has saved the UK public over £1 billion per year. However, there is still significant scope for further reducing food waste.

The Courtauld Commitment 2030 is a voluntary agreement that brings together organisations across the food system, including farmers, manufacturers, retailers, governments and NGOs, with the aim of reducing per capita ‘post-farm gate’ food and drink waste by 50% by 2030. The Commitment also includes targets to reduce water use and water stress in the supply chain (by sourcing fresh food from areas with sustainable water management) and to achieve a 50% reduction in GHGE associated with production and consumption of food and drink in the UK. The 2030 Commitment was launched in July 2021 as an extension of the Courtauld Commitment 2025, which previously set targets of 20% lower GHGE and food waste by 2025 across UK manufacture, retail, hospitality and food service, and household sectors.    

A recent progress report (November 2020) highlighted the UK as the first country globally to progress more than halfway towards meeting the UN target to reduce food waste by 50%, having reduced post-farm gate waste by 27% between 2007 and 2018. This indicates that achieving the ambitious target to cut food waste by 50% could be realised, although this will require ongoing efforts to reduce food losses and waste even further.

We shall all have a large part to play, as households are responsible for the major proportion of UK food waste (69.8%), with much lower ‘post-farm-gate’ losses from manufacturing (15.8%), the hospitality and food service sector (11.5%) and retail (2.9%). However, a survey by WRAP (the Waste and Resources Action Programme) in November 2020 found that, while 81% of people were concerned about climate change, less than a third (32%) said they saw a clear link between climate change and ‘throwing away food that could have been eaten’. Therefore, raising awareness of this issue appears important, such as through the recently launched Wasting food: it’s out of date campaign run by WRAP. The UK’s first Food Waste Action Week was held in 2021, aiming to raise awareness of the environmental consequences of wasting food, and promoting activities that help reduce the amount of food wasted. Read more about both these campaigns on the WRAP website.

Here are some simple tips that everyone can follow to reduce food waste in the home:

• Avoid cooking more food than is required: If you do have leftovers, consider taking them into work for lunch the next day or freezing them if you have a freezer. Also, you can incorporate cooked ingredients (like chicken and vegetables) into other meals, such as soups. Find a range of creative ideas for how to use leftover food on the Love Food Hate Waste campaign website. Cookbooks you may have at home can also be useful, as well as other free websites (such as BBC Food). Also consider the portion size when preparing foods, including any information available on the label, to avoid cooking or preparing more than is needed. For more information on portion size read our page 'Get portion wise!'.
• Plan meals before going to the shops: Only buy the items that you need and try to choose foods with the longest ‘use-by’ date if you are not sure when you will use them. Also, get into the habit of checking what you have in the fridge and freezer before going shopping, and aim to use foods that are approaching their ‘use-by’ date first, especially fruit and vegetables, meat and fish, cheese, milk and other dairy products.
• Set your fridge to the correct temperature: The average fridge temperature in the UK is 7°C; above the recommended range of 0-5°C. This means that more food is likely to spoil, especially items such as milk. The equivalent of 3 million glasses of milk is poured down household sinks in the UK every single day. Find out how to set your fridge correctly by reading the Love Food Hate Waste website.
• Know your date labels: This can help to prevent you wasting food. The Food Standards Agency provides the following advice on date labels: "The ‘best before’ date, sometimes shown as BBE (best before end), is about quality and not safety. The food will be safe to eat after this date but may not be at its best. Its flavour and texture might not be as good. A ‘use-by’ date on food is about safety. This is the most important date to remember. After the use-by date, don't eat it, cook it or freeze it. The food could be unsafe to eat or drink, even if it has been stored correctly and looks and smells fine. A lot of foods, including meat and milk, can be frozen before the use-by date though so plan ahead." Find out more by reading this page on date labels from the Food Standards Agency.
• Follow the storage instructions on food labels: This will help to ensure that foods stay fresh as long as possible. Find out more about freezing items to use at a later date by reading this page from the Love Food Hate Waste campaign.

Learn more about how to reduce household food waste, including shopping tips and recipes by reading the Love Food Hate Waste campaign website.

Last reviewed June 2021. Next review due June 2024.