Food choices, planetary health and social inequality

More of us now know that healthier diets can also be better for the planet. But there are barriers to making better food choices – and switching to a healthier, more sustainable diet can be harder for people on low incomes from Global-Majority backgrounds. Pan He’s research explains why

Recently food has become a hot topic for environmental scientists, and not just for nutritionists. Dietary patterns in developed countries such as the US have been criticised as unhealthy, for relying on intensive animal-product consumption.

However, they also contribute significantly to multiple environmental problems. Feeding livestock is quite water-intensive and emits carbon dioxide, methane and nitrous oxide, major greenhouse gases (GHGs) that trigger global heating. Given the massive medical costs of treating diseases linked to poor diet and the urgent need to cut our emissions to zero, the time has come for us to adjust our daily diets to become more sustainable. The question is, how?

Although research is still exploring what constitutes a healthy and planet-friendly diet, studies agree on the general principles, including sufficient high-quality protein, adequate amounts of essential fatty acids and sodium, enough dietary fibre and various types of vitamins and minerals. Food groups that supply these include lean meat, seafood, soy products, dairy products, vegetables, fruits, nuts, wholegrains and legumes in unprocessed forms.

Foods to avoid or at least restrict include those with added sugar and trans fats – processed food such as snacks, confectionary and sweetened beverages. Developed countries increasingly publish national dietary guidelines, setting out suggested a daily intake for different categories of food. And the 2019 EAT-Lancet Commission on healthy diets from sustainable food systems set out exactly what a planet and people-healthy diet would look like.

However, successive national studies in the US and many other developed countries reveal, in per capita terms, that people are eating too much red and/or processed meat, fat, added sugar and highly/ultra-processed food and not enough wholegrains, vegetable and fruits. This indicates that changing people’s diets would deliver co-benefits for human health and for environmental sustainability.

We could also adapt this win-win solution to developing countries undergoing rapid growth and socio-economic transformation. That process almost always also changes these countries’ food choices, “westernisation” reshaping people’s food choices. In contrast, undeveloped regions’ main challenge is undernourishment – and tackling this could create higher environmental impacts.

Unequal diets, unequal impacts

Just as there are differences across countries in dietary patterns and their health impacts, socio-economic differences also have diverse environmental outcomes. Our research, published in Nature journal, explores relationships between food, nutrition and environmental sustainability at subnational level. We looked at different socio-economic groups in the US to compare their food choices’ nutritional quality and environmental consequences.

The data is based on dietary records for the past decade of more than 40,000 individuals from the National Health and Nutrition Examination Survey. We used this data to calculate diets’ lifecycle greenhouse-gas emissions, blue-water footprint, land use and energy consumption. We also evaluated individual diets’ nutritional quality using the US Department of Agriculture’s (USDA) Healthy Eating Index.

The HEI scores individuals’ daily diets from 0-100; the higher the score the better the nutritional quality. We then analysed the statistics to work out differences in diets’ health and sustainability impacts by socio-economic status, including income level and educational attainment.

This showed that people with higher incomes and/or educational attainment have healthier diets indicated by higher HEIs but also generate larger environmental impacts. People who have higher socio-economic status eat more dairy products, livestock products and seafood, which have higher environmental impacts and emit more GHGs. These choices also provide more nutrients and fewer calories and are generally more expensive than the foods that people from lower socio-economic groups eat.

To explore whether changing to more sustainable diets would deliver environmental co-benefits for all the socio-economic groups who can afford to, we looked at both the environmental impacts and the costs to switch to food choices that score 100 in the HEI system. This showed that a shift to better diets by people from all groups would deliver similar reductions in GHG emissions, land use and energy consumption but would increase water consumption.

It also showed that the change would be more drastic for individuals from lower income, less educated backgrounds, in terms of how much food they eat in most categories. And this revealed differences in impact based on ethnic backgrounds too.

People from the lowest socio-economic groups are less likely to afford a healthy diet and more likely to feel this as a financial burden. But when we looked at this by ethnic background, we also found that 38 per cent of Black and Hispanic people in the lowest income and education group – twice the percentage of white people – cannot afford to switch to healthier diets.

And of those who can afford to switch, more than a third of Black and Hispanic individuals would feel the pinch, spending more than twice the national average on food based on percentage of income, at about 10 per cent.

Affordable and accesible

Our findings are supported by other studies published in The Lancet, that conclude that healthy, planet-sustainable diets are unaffordable for disadvantaged groups, globally and in the US. Healthy foods – fresh vegetables, fruit, seafood – that are natural are often also less calorie dense.

That’s one reason why people from disadvantaged backgrounds so often choose frozen meals, packaged or canned food and processed products. These foodstuffs provide cheap calories – but rarely the nutrients essential to our health. However they are cheap and filling, which is why so many people from disadvantaged groups choose them.

Time matters too. Home cooking can be a healthy choice. It helps people to eat higher-quality protein and vegetables, using less sodium, at a price that compares well with that of a fast-food restaurant. However, for many people time spent preparing food and cleaning the kitchen means sacrificing time to make money. This creates an opportunity cost. Again, for many low-income families this creates a time-income dilemma. And again, they turn to cheap, ready-to-eat foods with low nutrition density to fill that gap.

The problem becomes more acute for parents, needing to balance the competing demand to provide better-quality nutrition for growth against time for childcare.

Accessibility is another issue. The USDA has identified something it calls “food deserts”. These are communities with large numbers of people on low incomes who also struggle to access supermarkets or large grocery stores. People in these communities can struggle with time or transport to reach stores that sell healthier foods, or can’t afford the prices – or struggle with all three.

Population density tends to be low in these so-called food deserts, making it difficult and expensive to improve food security by increasing the density of grocery stores or investing in public transport.

Calls for change

In 2021, the USDA designed the Thrifty Food Plan, setting out suggestions for a low-cost, adequate diet. But when the Journal of Nutrition examined the time-cost impacts, it concluded that the plan was not thrifty – and that suggestions to improve quality of diet meant only more hardship for low-income households. Future initiatives need to consider time and cost as well as better food choices.

These need integrating into food-stamp programmes to tackle food insecurity among deprived groups, such as the US-based Supplemental Nutrition Assistance Program, in ways that support healthy food choices. There are opportunities, too, for better information and education about nutrition and diet.

A 2019 US-based study concluded that, since the mid-1990s, giving people better nutritional information has supported better food choices. Another study shows that making grocery stores more accessible only slightly reduces unequal nutritional quality.

The link between income and a household’s quality of nutrition comes down to educational level and nutrition knowledge, the Quarterly Journal of Economics concludes. What can we learn from this? Spreading knowledge is vital to break people’s bad habits and to guide them towards better food choices. Creating diet-education programmes is an easy win to change people’s choices to secure co-benefits for health and for the environment.

But we also need more research and pilot programmes, to support effective and equal policy changes. And we need to look beyond the US, to other countries and to global inequalities in relationships between food, nutrition and the environment.

Every country has its own challenges linked to inadequate diets and environmental impacts, reflecting its own socio-economic structures and dietary cultures. And we need more research to understand national and regional differences.

That creates more opportunity for behaviour scientists as governments seek to deliver the United Nations’ sustainable development goals, addressing people’s wellbeing, social equality, and environmental sustainability in all the countries of the world.

Pan He is a lecturer from the School of Earth and Environmental Sciences at Cardiff University. Her research addresses the environmental impacts of household consumption and environmental policy analysis:

Connect with her on Twitter using @Pan__He

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