Substituting one serving of beef per day nearly halves the carbon footprint of US diets

Implementing single-item food substitutions significantly reduced the carbon footprint and water scarcity footprint of participants’ diets, according to findings published in the American Journal of Clinical Nutrition.

For example, substituting poultry or pork for beef reduced carbon and water scarcity footprints by 48.4% and 29.9%, respectively, according to Diego Rose, PhD, MPH, RD, a professor of nutrition and food security in the School of Public Health and Tropical Medicine at Tulane University, and colleagues.

“There’s a lot of overlap between healthy choices and environmentally friendly choices,” Rose told Healio.

The researchers used 2005 to 2010 data from the National Health and Nutrition Examination Survey (NHANES) to assess the 24-hour dietary recall of 16,800 adult respondents. Rose and colleagues estimated the greenhouse gas emissions (GHGE) and irrigated water use associated with all foods reported using previously developed databases. The environmental impacts of respondents’ diets were summed to create carbon and water scarcity footprints. Also, the researchers assessed the quality of food choices using the Healthy Eating Index (HEI). Food items with the highest impact on GHGE and other selected foods were hypothetically substituted by Rose and colleagues for calorically equivalent, less environmentally impactful items. The footprints of these foods were calculated before and after the hypothetical substitutions.

Among the respondents, 52.1% were women and a majority (36.9%) were aged 30 to 49 years. Also, 70.1% were non-Hispanic white, 11.6% were non-Hispanic Black and 12.7% were Hispanic.

Consumption trends

The researchers substituted beef for 3,320 respondents (about 20% of the NHANES cohort) who reported eating this food item on their recall day. Most (86%) of substitutions were made to diets ranked in the top two quintiles of dietary GHGE. Among the respondents who had a substitution, 88% consumed the high-impact food once during the recall day, 11% consumed the food twice and 1% consumed the food three times or more. Men and younger adults were more likely to have a high GHGE food item substituted.

Single-item substitutions

Substituting poultry or pork for one serving of ground beef per day yielded the greatest average 1-day reduction in GHGE, which decreased by 3.73 kg CO2-eq (48.4%). Substituting beef for another animal product would ensure “consumer acceptability,” Rose and colleagues noted. While the study did not include plant-based meat analogues, research has shown that the carbon footprint of these products is much lower than that of ground beef and somewhat lower than that of turkey, they wrote.

Also, with the beef substitution, the mean HEI score for respondents’ new diets was 3.6 points higher than respondents’ original diets (P < .001).

Other replacements that yielded significant GHGE reductions included substituting shrimp with cod (34.1% reduction) and dairy milk with soymilk (8.1% reduction). Moreover, the greatest reduction in the water scarcity footprint came from replacing asparagus with peas (48.2% decrease) and almonds with peanuts (30.4% decrease).

Overall, the water scarcity footprint for new diets averaged 972 liter-eq per 2,000 kcal less than respondents’ original diets (P < .001), a mean reduction of 29.9%. If substitutions were made to all respondents’ diets, the overall 1-day GHGEs would have decreased by 9.6% and water scarcity footprints would have reduced by 5.9%.

“I think people who are motivated to make changes should be given the information that will allow them to make those changes, and particularly not just for health but also for environmental benefits,” Rose said. “Physicians can help signal the importance of that, because they are the trusted authority in terms of their patient's health.”

However, the U.S government has lagged in providing dietary guidance that includes information about sustainability, according to Rose.

“There are many governments in the world that have included information about environmental sustainability in their dietary guidance and have organized their dietary guidance around that issue — not just included information, but actually modified it,” he said.