New Study Reveals Best and Worst Diets for Health and the Planet

A new study by Tulane University has compared six popular diets for their nutritional quality and environmental impact. The findings highlight stark differences in sustainability and health benefits between eating styles. While some diets excelled in both areas, others fell short on key measures.

The research analysed omnivore, Mediterranean, DASH, vegetarian, pescatarian, vegan, keto, and paleo diets. Omnivore diets ranked in the middle for both nutritional quality and sustainability. In contrast, plant-focused diets like Mediterranean and DASH performed better in both categories.

The pescatarian diet scored highest for nutritional quality, followed by vegetarian and vegan options. These diets also showed lower carbon footprints. The vegan diet produced the least emissions—just 0.7 kg of carbon dioxide per 1,000 calories. At the other end of the scale, keto and paleo diets ranked worst. The keto diet generated nearly 3 kg of carbon dioxide per 1,000 calories, while paleo produced 2.6 kg. Both also scored poorly on nutritional value. The study underscored how food choices affect the planet, with the global food system contributing 34% of greenhouse gas emissions. Beef production alone emits 8 to 10 times more than chicken and over 20 times more than nuts or legumes. Cutting meat consumption, the research suggests, can significantly reduce an individual's carbon footprint.

The findings reveal clear winners and losers among popular diets. Plant-based and pescatarian diets offer strong nutritional benefits while minimising environmental harm. Meanwhile, keto and paleo styles lag in both sustainability and dietary quality, according to the analysis.