Vegan and pescatarian diets win for health and climate, study reveals

A new study from Tulane University has compared the environmental and nutritional impact of six popular diets. The findings highlight how food choices directly affect both personal health and climate change. Researchers examined carbon footprints, land use, and water consumption alongside nutritional quality.

The study analysed eight diets in total, including standard Western, vegetarian, pescatarian, vegan, Mediterranean, DASH, semi-vegetarian, and optimised versions. Nutritional value was measured using the Alternate Healthy Eating Index (AHEI-2010), while environmental impact was assessed through greenhouse gas emissions, water use, and land demand.

The vegan diet produced the lowest carbon footprint, emitting just 0.7 kg of CO₂ per 1,000 calories. Vegetarian diets followed closely, with pescatarian options also scoring well for sustainability. Omnivore diets fell in the middle, though plant-heavy versions improved both environmental and nutritional outcomes.

In contrast, the keto diet generated nearly 3 kg of CO₂ per 1,000 calories—the highest of all. The paleo diet also performed poorly, with 2.6 kg of CO₂ emissions and the lowest nutritional ratings. Pescatarian diets ranked highest for nutritional quality, with vegetarian and vegan diets not far behind.

The research aligns with a 2021 UN-backed report, which found that 34% of global greenhouse gas emissions come from food production. This underscores how individual dietary habits can play a significant role in climate efforts.

The study confirms that shifting toward plant-based or pescatarian diets can reduce environmental harm while improving nutrition. Keto and paleo diets, however, remain the least sustainable and least nutritious options. These findings provide clear data for those looking to make climate-conscious food choices.