I spotted this week’s paper on the Medical Xpress news website and a couple of people also emailed me about it. The headline I saw was “Keto vs. vegan: Study of popular diets finds over fourfold difference in carbon footprints” (Ref 1). The paper behind the news headline was called “Popular diets as selected by adults in the United States show wide variation in carbon footprints and diet quality” and it was by O’Malley et al (Ref 2).
The aim of this study was to estimate the carbon footprint and diet quality of what were called “popular diets” among US consumers. This paper used data on 16,412 people from the NHANES 2005-2010 population study. The NHANES study was based on one 24-hour recall of diet from the participants. Based on the diet information from this one recollection, the researchers assigned participants to one of six diets: vegan, vegetarian, pescetarian, paleo, keto and all other diets. We’ll cover how the diets were defined next.
The authors said that they then calculated the average daily greenhouse gas emissions (GHGE) in kilograms of CO2 equivalents per 1,000 calories. The word estimated would be more accurate. The GHGE were estimated using a database that the authors had developed previously. Diet quality was assessed using a standard US index called the Healthy Eating Index (HEI).