Simple dietary substitutions can slash US carbon footprint by over 35%

By Vijay Kumar MalesuReviewed by Lily Ramsey, LLMOct 31 2023

In a recent study in Nature Food, researchers evaluated the environmental and health impact of simple food substitutions in the United States (U.S.) diet.

Study: Simple dietary substitutions can reduce carbon footprints and improve dietary quality across diverse segments of the US population. Image Credit: Jacob Lund/Shutterstock.com

Background 

Our dietary choices greatly influence personal health and global environmental concerns. About a third of human-induced greenhouse gas emissions stem from food production, directly linking our diets to health issues like obesity and heart disease. The Paris Agreement highlights the urgent need to modify our eating patterns.

Adopting diets emphasizing fruits, vegetables, and legumes while reducing red and processed meats can minimize carbon emissions and promote better health. However, the multitude and complexity of available food choices make habit changes challenging.

Promoting simple dietary substitutions, such as opting for poultry over beef, can be a more feasible and impactful solution than drastic alterations like becoming vegetarian.

Given the complexities of food choices and the challenges in changing eating habits, further research is crucial to identify simple dietary substitutions that can benefit both the environment and human health across diverse populations.

About the study 

The present study drew on data from respondents of the National Health and Nutrition Examination Survey (NHANES) 2015–2016 cycle, a survey representative of the non-institutionalized U.S. civilian population. This survey's findings matched the most current data on greenhouse gas emissions related to food production.

Researchers analyzed data from 7,753 participants aged two and above who had provided a valid 24-hour dietary recall. The dietary information was collected using the Automated multiple-pass method by trained interviewers. Adults aided in the recall process for children aged between 6 and 11, and for those under 5, an adult proxy completed the recall.

This research primarily centered on greenhouse gas emissions, a critical environmental impact of food production. The emissions data were derived from the Food Recall Impacts on the Environment for Nutrition and Dietary Studies Database. This database offered insights into the greenhouse gas emissions tied to the production of specific food items, as reported by the participants.

The study's core objective was pinpointing high-carbon-impact foods and proposing viable lower-carbon alternatives. Findings revealed that four major food groups—mixed dishes, proteins, dairy, and non-alcoholic beverages—accounted for approximately 85% of U.S. dietary carbon emissions.

Researchers subsequently sought feasible substitutions within these pivotal groups. As an illustration, they recommended replacing a beef meatloaf with one crafted from chicken or turkey.

Lastly, the study assessed the potential impacts of these dietary alterations on two main outcomes: overall dietary quality and dietary carbon footprints. The research utilized the Healthy Eating Index (HEI) 2015 scores to evaluate dietary quality since diets aligned with HEI are known to correlate with a reduced risk of various diseases.

The analysis and simulations were conducted considering the complex survey design of the NHANES, with findings subject to review and approval by relevant Institutional Review Boards.

Study results 

The study focused on 7,753 respondents aged two years and above who participated in NHANES during 2015-2016. Within this group, roughly 51.5% were women, with 21% below 18 years and 22% 60 years or older.

The data indicated a correlation between consumption of high-carbon-impact food and age, race, and ethnicity. However, there was no significant association with gender, educational background, or family income. 

The researchers identified potential food substitutions within four main categories: proteins, mixed dishes, milk and dairy, and beverages. The possible substitutions varied within these categories, with drinks having 79 and mixed dishes having 180. The primary objective was to replace high-carbon-impact foods with similar alternatives that have a lower carbon impact.

For instance, in the protein group, beef was frequently replaced with poultry. Mixed dishes saw substitutions of beef or pork entrees with poultry or vegetarian versions. Milk and dairy products transitioned from animal-based to soy or almond-based alternatives and beverage swaps mostly involved replacing juice with whole fruits.

Implementing these dietary changes could significantly lower the carbon footprint associated with food consumption. For example, protein substitutions could lead to a 50.2% reduction in the dietary carbon footprint, while mixed-dish substitutions could result in a 52.6% reduction.

Although the reductions were more modest for milk, dairy, and beverages, the potential positive impact on a broader scale remains significant. For instance, protein substitutions alone could reduce the overall dietary carbon footprint by 15.1% when scaled to the entire U.S. population.

If all suggested food swaps were adopted across the four categories, there is potential for a 37.5% reduction in the U.S.'s carbon footprint from food consumption.

The research also hinted at variability among different demographics. Generally, adults, especially males, exhibited a higher reduction in their dietary carbon footprints than children and females.

When observing the data from a racial and ethnic perspective, some differences emerged. For example, Asian respondents showed slightly smaller protein swap reductions than non-Hispanic Black, Mexican-American, and other Hispanic groups. 

Apart from the environmental implications, these dietary changes promise better health outcomes. The simulated protein substitution could enhance the average HEI score by 4.3%, while mixed-dish changes could lead to a 10.3% improvement. These enhancements in dietary quality often result from increased beneficial nutrients like seafood, plant proteins, and fatty acids.

Yet, some reductions in essential components like sodium and zinc were noted. Across all demographic groups, the diet quality generally improved, with younger age groups and males benefiting more. The extent of improvement, however, varied based on racial and ethnic backgrounds.

For example, mixed-dish substitutions seemed most beneficial for Mexican-American or other Hispanic respondents, whereas beverage substitutions favored non-Hispanic Black individuals.