01 Mar The dietary trio of healthy, nutritious and climate-friendly
A recent study and accompanying editorial have compared dietary nutrient density and diet-related greenhouse gas emissions to understand whether individuals consuming more nutritious diets with lower carbon footprints have a longer lifespan than others.
The short editorial highlights some of the issues in interpreting data for the relationships between mortality and food. Nutrient density, as measured here, can be assessed through multiple metrics. Similarly, climate impact can be measured in many ways, here via greenhouse gas emissions in CO2-equivalents.
Although the impact of nutrition on death rate is an important consideration in assessing the impact of diets on health, it is limited and does not account for broader lifestyle impacts on mortality.
Similarly, although climate impact is an important consideration in assessing the impact of diet on the environment, land, water, and fertiliser use (among other factors) must also be considered in assessments of the environmental efficiency of diets.
Within these limitations the study found several interesting associations, with notable differences between women and men.
In the female cohort, mortality was 13% lower for those consuming diets with a high nutrient density and a low climate impact compared to those on low nutrient density and high climate impact diets. However, the same reduction in mortality was found for those consuming diets with a high nutrient density and high climate impact, indicating that nutrient density was the most important factor in the reduced mortality rate.
For men, mortality was 11% higher for diets having a low nutrient density and low climate impact compared to diets having a low nutrient density and high climate impact. It was suggested that this was due to sugar content: sugar has a small climate impact, but a clear negative impact on health when overconsumed.
The editorial makes some useful suggestions for how improvements can be made to such studies, such as considering food intake rather than reducing the assessment to individual nutrients. These results emphasise that climate-friendly diets are not always healthy, and vice versa, but that healthy, climate-positive diets can be achieved.