Sustainable Diets and Not-So-Sustainable Consumers

Over the past years, the link between food and the environment has become increasingly clear. Certain foods have a much higher overall environmental impact than others – caused by the whole production chain, from farm to fork. Additionally, there is increasing evidence of the links between diet and health. Because this research has been undertaken in such separate fields – medicine on the one hand, and environmental, climate, or agricultural sciences on the other, the topics of dietary-related health impact and dietary-related environmental impact have not really touched. This is now changing, with guidelines for ‘sustainable diets’, such as those by the FAO, combining both for the first time.

Interesting insights with regard to the sustainability of diets were recently published by researchers from the University of Michigan in the US. They combined large-scale real-life dietary information (from food questionnaires filled in by almost 17,000 representative Americans, gathered in a long-term programme called NHANES) with the environmental impact of the different foods. So, for the first time in the US, this is not a theoretical study of the environmental impact of food, but a study of large numbers of actual, real, Americans and the food they eat.

Among other things, the study shows that 20 percent of US consumers have such high-carbon-footprint diets, that they account for nearly 50 percent of the total food-related emissions. Put in another way, the greenhouse gas (GHG) emissions in that same top 20 percent are almost 8(!) times higher than in the bottom 20 percent of diets. Partly, this is because the people in the top 20 percent simply eat more food overall – their calorie intake is 2.3 times higher than that of the bottom 20 percent. And so, while the researchers do not further investigate the calorie issue, one could perhaps safely assume that eating less (or changing their menu) would, aside from lowering the burden on the planet, also be healthier for this top 20 percent of consumers. Obesity, resulting from prolonged intake of too many calories, is associated with health problems including cardiovascular disease and diabetes – as similar research based on the NHANES data also consistently shows.

Besides the amount of food, the type of food eaten plays a big role. Within the top 20 percent of highest-footprint diets, 70 percent of the total GHG emissions are caused by meat consumption (of which a whopping 91 percent is reported to be beef). In the bottom 20 percent of diets, only 27 percent of emissions are caused by meat (and the people in this group, perhaps not surprisingly, eat mostly poultry, at 55 percent of all their consumed meat). Thus, the amount of meat consumed matters, but also the type of meat.

Finally, the study provides an interesting insight into the amount of food wasted, approximated at around 25 percent by the researchers. Reducing food waste would directly reduce the environmental footprint of food overall. In the US, similar to other developed nations, food waste is mainly generated at the consumer level – and if consumers waste less, they then have to buy less (saving money in the process), and that effect will ripple back through the value chain and result in fewer resources needed to produce food – and thus less environmental pressure.

A second study, with a similar approach and representing over 34,000 French consumers (known as NutriNet-Santé), was published by a group of researchers from the Sorbonne University in Paris, France. The results show that the 20 percent of people who relatively eat the most plant-based foods (and hence the least meat) also exercise more, smoke less, are more highly educated, and eat less fast food and candy. They also consume more healthy fats, more fibres, and more of most micronutrients. All in all, the researchers conclude that this 20 percent group comes closest to the French government’s dietary guidelines (but they still don’t quite reach them), and lead an overall healthier lifestyle. This top 20 percent seems to represent that group of consumers who make conscious decisions about the food they eat, for various reasons – including for instance concerns over their own, or their children’s, health or the environment.

In the French top 20 percent meat-eating group, 80 percent of the total GHG emissions are caused by animal products, matching the results from the US. Furthermore, this group (who eat more than double the meat, and almost triple the dairy, compared to the 20 percent who eat the least meat) causes double the GHG emissions, almost double the land occupation, and 40 percent higher energy use compared to the 20 percent who eat the least meat. Other recent publications based on the same French consumer diet dataset suggest that high consumption of strongly processed foods, or of red meats, increases a person’s risk to get cancer, and lower dietary quality overall is related to increased risk of cardiovascular disease. Finally, the French study – again, similar to the study from the US – shows that the high environmental impact of the top 20 percent meat eaters is to a large extent caused by beef, which is eaten relatively more by the top 20 percent of meat eaters when compared to other meats. All in all, the French results may be a bit less extreme compared to the study from the US, but they certainly point in the same direction.

The FAO defines sustainable diets as: ‘Those diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations. Sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable; nutritionally adequate, safe and healthy; while optimizing natural and human resources.’ They also give practical guidelines: sustainable diets should be diverse, enough but not too much, based around minimally-processed tubers, whole grains, legumes, fruits, and vegetables. They can include animal protein (such as meat and dairy, and sustainable fish), but in moderation. Finally, the diet should include unsalted seeds and nuts, oils and fats with a beneficial Omega 3:6 ratio, tap water rather than other beverages, and very limited consumption of foods high in fat, sugar, or salt, or those low in micronutrients.

It seems that, based among others on the academic research highlighted in this article, actual real-life consumers on average still have some way to go to reach a sustainable diet such as advocated by the FAO. Perhaps, the concept of sustainable diets to a certain extent ignores the fact that there still is considerable technological potential to increase the sustainability of food production. Technology is marching ahead, but the commercialisation process is often slow, at least partly caused by the absence of market rewards (or in some case by the fact that the player profiting from the technology is different from the one who has to make the investment).

Nevertheless, the coming years will undoubtedly see increasing efforts to steer towards the general direction of the FAO’s definition. This will on the one hand be driven by health-conscious and increasingly well-informed consumers. But we may also expect increasing government interference, as the links between food, health, and environment become clearer, especially if the speed of market change remains sluggish.

Martin C Heller et al 2018, Greenhouse gas emissions and energy use associated with production of individual self-selected US diets, Environ. Res. Lett. 13 044004

Lacour C et al 2018, Environmental impacts of plant-based diets: how does organic food consumption contribute to environmental sustainability? Front. Nutr. 5:8

Author: Maartje van den Berg