Carbon footprint associated with dietary guidelines, varies between seven countries

Greenhouse gas emissions associated with national dietary guidelines advocating a healthy diet vary greatly between countries, with United States guidelines having the largest carbon footprint and India having the smallest, according to a new study published in the Nutrition Journal.

The study involved seven countries, Germany, India, the Netherlands, Oman, Thailand, Uruguay, and the U.S. The variations result from differences in recommendations for and consumptions of individual foods within the six main food groups, protein foods, dairy, grains, fruits, vegetables, and oils and fats.

For the study, researchers investigated differences in greenhouse gas emissions associated with different dietary guidelines, comparing the dietary guidelines and food consumption patterns.

The authors found that the carbon footprint of India's dietary guidelines was comparatively low, with the recommended diet associated with the equivalent of 0.86 kilograms carbon dioxide (CO2) per day, compared to the U.S. with 3.83 kilograms CO2 per day.

The carbon footprint of the U.S. dietary guidelines was found to be about 1.2 times that of the Netherlands, equivalent to 2.86 kilograms CO2 per day, and about 1.5 times that of Germany, equivalent to 2.25 kilograms CO2 per day. The U.S. vegetarian dietary guidelines, while much lower than the main guidelines in terms of greenhouse gas emissions or equivalent to 1.80 kilograms CO2 per day, was still over twice that of India's largely due to the high U.S. dairy recommendation.

The authors also found that the principal difference between the dietary guidelines of the various countries was the wide range of daily recommended amounts for each food group, particularly protein and dairy foods. Daily recommended amounts of dairy foods ranged from 118 milliliters per day for Oman to 710 milliliters per day for the U.S. The greenhouse gas emissions associated with these two recommendations were equivalent to 0.17 and 1.10 kilograms CO2 per day, respectively. The greenhouse gas emissions associated with the protein food recommendations ranged 0.03 kilograms CO2 per day in India to 1.84 kilograms CO2 in the U.S., for recommended amounts of 75 grams per day and 156 grams per day, respectively.

Guidelines also varied in terms of which foods were included in each food group. Protein food recommendations in Germany and Uruguay only included animal proteins, the U.S. and Thailand recommended a full spectrum of plant and animal protein foods, whereas India recommended just plant proteins. The U.S. vegetarian guideline recommended plant proteins, as well as dairy and eggs.

The authors caution that the study only considers a single environmental impact of diets, greenhouse gas emissions. Other environmental impacts, such as land and water use, should be considered when evaluating the overall impact of a diet. The study is restricted to the daily quantitative recommendations of seven countries' dietary guidelines, which may limit its generalizability to other countries.