Using the latest scientific research, many governments provide official guidance on how best to eat in order to stay healthy. In the UK, for example, the recommended daily allowance for a woman aged 19 to 64 years includes 2000 calories, 45g of protein and 78g of fat. Few people know these figures off by heart or how they correspond to the food they actually eat, and fewer still use them as an actual benchmark for their own diet. For most of us, there just isn’t the time. At best, you might look at the traffic-light coded information on food packaging, but if you’re like me you’ll probably still buy your pack of biscuits. Nonetheless, most people still consider following recommended guidelines to be an excellent, if ambitious, way to keep fit and healthy.
What you may not usually consider, however, is that the benefits of nutritional guidelines extend beyond personal wellbeing to the health of the planet. A recent study from Leiden University reviewed the environmental impacts of nationally recommended dietary guidelines (NRDs) from a range of countries and compared them to the effects of actual average diets. It estimated that greenhouse gas emissions in high-income countries would fall by between 13% and 25% if the average dietary intake shifted from current averages to match NRDs. This would be accompanied by a 10-21% decrease in eutrophication – the ecologically harmful saturation of water sources with chemicals used in agriculture – and a 6-18% fall in land use, creating more space for nature. Although the scale of this effect would be diminished in upper-middle and lower-middle income countries, a switch to NRDs would still produce 10-21% and 1-12% decreases in emissions respectively. It is only in low-income countries where NRD matching would lead to increased emission rates.
This correlation with wealth is the result of high rates of overnutrition in richer countries, rather than any major differences in government guidelines. Given the pace of development at a global level and the growing wealth of developing countries it isn’t surprising that a complete shift in human dietary intake towards NRD averages would produce a net benefit to the environment. The authors of the Leiden University study estimated net CO2 emissions would fall by 4.3-10.6 gigatonnes per year if the average diets of all countries equalled their respective NRDs. This study really highlights the important connections between diet, environment and health. ‘Health’ is about more than eating a balanced diet and getting proper treatment for an illness, it is also about the world we live in – the state of the earth’s living systems, the instability of the climate, and the effects of a changing world on people everywhere.
Interestingly, no governments as of yet explicitly consider the environmental effects of diet when producing their NRDs, but policy makers are already starting to join the dots as more and more studies linking health to the state of the environment find their way into the scientific literature. Although we can’t be expected to crunch the numbers at every mealtime it is worth bearing in mind the broader picture behind dietary guidelines and the food on our plates. And next time you’re glancing at the traffic lights in the supermarket, remember there’s more than one reason to go green.
For more details, read the full study by Behrens et al. (2017) at http://www.pnas.org/content/early/2017/11/28/1711889114.full