Every year, it seems that a new diet trend emerges, each one claiming to be the best option for our health, weight, and longevity. Some people are advocates of the ketogenic diet (a diet high in fat and low in carbs), while others believe we should return to our ancestral roots by adopting the paleo diet (a diet that avoids anything our early ancestors would not have been able to eat). On the other hand, some people focus on the environmental cost of a diet; many choose to go vegan or vegetarian in order to reduce their impact. Given such a variety of opinions, how can science help inform us about what diet is ideal for both our health and the environment? Should we venerate vegetables, pack on the protein, focus on fats, or some combination of these? Does a consensus exist?
In 2017, a research team led by Alice Rosi analyzed the water, carbon, and ecological footprints of omnivores (people who eat both meat and plants), ovo-lacto-vegetarians (people who do not eat meat but do eat milk and eggs), and vegans. 153 adults recorded everything they ate for seven days and an environmental impact database was used to calculate the effect of their diets on the environment. Overall, the omnivorous diet had a significantly worse environmental impact in terms of water, carbon, and ecological impact than vegetarian or vegan diets (which were shown to be equivalent environmentally). Other studies have found that veganism is the best diet for the environment due to its decreased production of harmful greenhouse gases and that omnivorous diets have the highest level of greenhouse gas emissions (Chai et al., 2019; Rabés et al., 2020),
The results of this research all suggest that adopting a vegetarian or vegan diet is the best option for environmental sustainability. However, going vegetarian or vegan isn’t feasible for everyone, as it requires time and effort to plan out balanced meals and to make sure that you are getting your full nutritional requirements every day—especially vitamins like B12, which are only found naturally in meat. Studies have shown that the Mediterranean diet—a diet consisting of high amounts of fruits, vegetables, complex carbohydrates and legumes; low amounts of fish and meat; and olive oil as the main fat source in the diet—is actually perhaps the best diet possible for overall health and wellbeing. One paper, a meta-analysis of a large number and variety of studies, found that the Mediterranean diet was associated with a strong reduction in overall mortality, and the risk of mortality caused by cancer, heart disease, and degenerative brain conditions (Sofi et al., 2010)
But, how does the environmental impact of a low-meat, Mediterranean diet compare to that of a no-meat diet? A theoretical study of the widespread implementation of the Mediterranean diet in Spain suggests that if the population adopted a Mediterranean diet, it would be responsible for the reduction of greenhouse gasses by 72%, land use by 58%, and energy consumption by 52%. In comparison, maintaining the status quo and eating a typical high-meat diet could be responsible for an increase of up to 70% in these categories (Sáez-Almendros et al., 2013)! Thus, even reducing a bit of meat from our diet—not entirely—can have huge impacts.
Research has shown us that if you can challenge yourself to eat a little less meat than you usually do, perhaps by adopting Meatless Mondays, or limiting yourself to meat a few days a week, while focusing your diet around fruits, vegetables, healthy grains, then you’ll be helping to do your part—both for your body and the planet!
You can learn more about the Mediterranean diet here: https://www.health.harvard.edu/blog/a-practical-guide-to-the-mediterranean-diet-2019032116194
Chai, Bingli Clark, et al. “Which Diet Has the Least Environmental Impact on Our PLANET? A Systematic Review of Vegan, Vegetarian and Omnivorous Diets.” Sustainability, vol. 11, no. 15, 2019, p. 4110., doi:10.3390/su11154110.
Rabès, Anaëlle, et al. “Greenhouse Gas Emissions, Energy Demand and Land Use Associated with Omnivorous, Pesco-Vegetarian, Vegetarian, and Vegan Diets Accounting for Farming Practices.” Sustainable Production and Consumption, vol. 22, 2020, pp. 138–146., doi:10.1016/j.spc.2020.02.010.
Rosi, Alice, et al. “Environmental Impact of Omnivorous, Ovo-Lacto-Vegetarian, and Vegan Diet.” Scientific Reports, vol. 7, no. 1, 2017, doi:10.1038/s41598-017-06466-8.
Sáez-Almendros, Sara, et al. “Environmental Footprints of Mediterranean versus Western DIETARY Patterns: Beyond the Health Benefits of the Mediterranean Diet.” Environmental Health, vol. 12, no. 1, 2013, doi:10.1186/1476-069x-12-118.
Sofi, Francesco, et al. “Accruing Evidence on Benefits of Adherence to the Mediterranean Diet on Health: An Updated Systematic Review and Meta-Analysis.” The American Journal of Clinical Nutrition, vol. 92, no. 5, 2010, pp. 1189–1196., doi:10.3945/ajcn.2010.29673.