Mercedes Sotos-Prieto
Nutritional epidemiologist at CIBERESP and IMDEA Food, professor at the Autonomous University of Madrid, and assistant professor at the Harvard School of Public Health
This study presents a robust methodological design for observational studies. It is based on two large prospective cohorts, NHANES in the US and UK Biobank in the UK, which include a large sample size of more than 168,000 people. In addition, they have supplemented the study with a meta-analysis of 37 previous studies involving more than 3 million participants. They have taken into account the main confounding variables, i.e., those that could distort the actual association, and have performed sensitivity analyses to confirm the consistency of the findings. In addition, an assessment of the environmental impact of the diet has been incorporated, adding an interesting dimension in the current context.
It confirms previous results carried out in various population cohorts on the benefits of a planetary health diet. This diet is characterized by being based on high-quality plant-based foods and taking into account consumption limits for foods that are related to human health and the health of the planet. The results are consistent with previous research in different countries, including two studies carried out by our research group, one of them in Spain, where we have also studied how this diet compares to the Mediterranean diet in terms of health and environmental impact (both share similar characteristics in that they are based mainly on the consumption of whole plant foods).
Like any observational study, this work has some limitations. For example, UK Biobank participants tend to have healthier lifestyles than the general population, which may limit the generalizability of the results. It is also important to note that diet was assessed at a single point in time, without taking into account possible changes over time. Furthermore, although many factors were adjusted for, there is always the possibility of residual confounding. Although they assess environmental impact by carbon footprint, there are also other indicators. Finally, some heterogeneity was observed in the meta-analysis, especially in total mortality, due to differences in how diet was measured and adherence indices were calculated.
We know that the implications of following diets based on high-quality plant-based foods are important for disease prevention and can help reduce the burden of chronic diseases and premature mortality. In addition, by adopting this pattern, we are helping planetary health by reducing greenhouse gas emissions associated with food production.
In Spain, where the Mediterranean diet is already part of the food culture, the transition to this pattern could be easier and/or complementary. In fact, in our study, in a representative Spanish population, we saw that the planetary health diet had similar benefits to those of the Mediterranean diet, both in terms of health and sustainability, which helps people choose one pattern or the other based on their preferences. This helps to continue promoting food policies that integrate health and environmental criteria, including the consumption of plant-based foods, the reduction of red and processed meats, ultra-processed foods, and sugary drinks, and the increase of legumes, fruits, vegetables, nuts, and whole grains.