suggests a new analysis that reveals meat-based, as well as keto and paleo diets, to be the worst on both measures.
The research was published online in The American Journal of Clinical Nutrition.
To obtain a real-world view on the environmental and health impact of diets as consumed by U.S. adults, the team examined a nationally representative survey of the 1-day eating habits of more than 16,000 individuals.
This revealed that the best quality diet was pescatarian, followed by vegetarian and vegan diets. Omnivore diets, although less healthy, tended to score better than keto and paleo diets, which were the lowest ranked.
Both keto and paleo diets tend to be higher in animal foods and lower in plant foods than other popular diets, the researchers explain in their study, and they both have been associated with negative effects on blood lipids, specifically increased LDL cholesterol, raising concern about the long-term health outcomes associated with these diets.”
Analysis of the environmental impact of the different eating patterns showed that the vegan diet had the lowest carbon footprint, followed by the vegetarian and pescatarian diets. The omnivore, paleo, and keto diets had a far higher carbon footprint, with that of the keto diet more than four times greater than that for a vegan diet.
“Climate change is arguably one of the most pressing problems of our time, and a lot of people are interested in moving to a plant-based diet,” said senior author Diego Rose, PhD, MPH, RD, in a press release.
“Based on our results, that would reduce your footprint and be generally healthy,” noted Dr. Rose, nutrition program director, Tulane University, New Orleans.
To determine the carbon footprint and quality of popular diets as they are consumed by U.S. adults, Keelia O’Malley, PhD, MPH, Amelia Willits-Smith, PhD, MSc, and Dr. Rose, all with Tulane University, studied 24-hour recall data from the ongoing, nationally representative National Health and Nutrition Examination Survey (NHANES) for the years 2005-2010.
The data, which was captured by trained interviewers using a validated tool, was matched with the U.S. Department of Agriculture Food Patterns Equivalents Database to categorize the participants into one of six mutually exclusive categories: vegan, vegetarian, pescatarian, keto, paleo, or omnivore.
The omnivore category included anyone who did not fit into any of the preceding categories.
The environmental impact of the diets was then calculated by matching the established greenhouse gas emissions (GHGE) of over 300 commodities to foods listed on the NHANES, which was then summarized for each individual to give a carbon footprint for their 1-day diet.
Finally, the quality of their diet was estimated using the 2010 versions of the Healthy Eating Index and the Alternate Healthy Eating Index, both of which award a score to food components based on their impact on health.
Overall, 16,412 individuals were included in the analysis, of whom 52.1% were female.
The most common diet was omnivore, which was followed by 83.6% of respondents, followed by vegetarian (7.5%), pescatarian (4.7%), vegan (0.7%), keto (0.4%), and paleo diets (0.3%).
The lowest carbon footprint was seen with a vegan diet, at an average of 0.69 kg of carbon dioxide equivalents per 1,000 kcal consumed, followed by a vegetarian diet (1.16 kg of carbon dioxide equivalents per 1,000 kcal) and pescatarian diet (1.66 kg of carbon dioxide equivalents per 1,000 kcal).
The highest carbon footprints were observed with the omnivore (2.23 kg of carbon dioxide equivalents per 1,000 kcal), paleo (2.62 kg of carbon dioxide equivalents per 1,000 kcal), and keto diets (2.91 kg of carbon dioxide equivalents per 1,000 kcal).
In terms of diet quality, the pescatarian diet was ranked the highest on both eating index scores, followed by the vegetarian, then vegan, diets. The order of the three lowest scores depended on the index used, with either the keto or paleo diet deemed to be the worst quality.
Analysis of individuals following an omnivore diet suggested that those who ate in line with the DASH or Mediterranean diets had higher diet quality, as well as a lower environmental impact, than other people within the group.
Hence, Dr. Rose observed, “Our research ... shows there is a way to improve your health and footprint without giving up meat entirely.”
The researchers acknowledge that the use of 1-day diets has limitations, including that whatever individuals may have eaten during those 24 hours may not correspond to their overall day-in, day-out diet.
The study was supported by the Wellcome Trust. Dr. Rose declares relationships with the Center for Biological Diversity, the NCI, and the Health Resources and Services Administration. Dr. Willits-Smith has received funding from CBD and NCI. Dr. O’Malley has received funding from HRSA.
A version of this article first appeared on Medscape.com.