Healthy plant-based dietary patterns were associated with better environmental health, while less healthy plant-based dietary patterns, which are high in foods like refined grains and sugar-sweetened beverages, require more cropland and fertilizer, according to a new study led by researchers. At Harvard TH Chan School of Health and Brigham and Women’s Hospital. The findings also show that red and processed meats have the highest environmental impact of all food groups in the participants’ diet, producing the largest share of greenhouse gas emissions and requiring the most irrigation water, cropland and fertilizer.
“The differences between plant-based diets were surprising because they are often portrayed as universally healthy and good for the environment, but they are more important than that,” said Aviva Musics, a postdoctoral research fellow in the Department of Nutrition at the Harvard Chan School. Corresponding author of the study. “To be clear, we are not asserting that less healthy plant-based diets are worse for the environment than animal-based diets. However, our findings show that plant-based diets can have different health and environmental impacts.”
The study, which is one of the first to look simultaneously at the health and environmental effects of different plant-based diets, was published in the November 2022 issue of Lancet Planetary Health.
Previous research has documented that different types of plant-based diets have different health effects. For example, a plant-based diet high in whole grains, fruits, vegetables, nuts, legumes, vegetable oils, and tea/coffee is associated with a reduced risk of chronic disease, while a plant-based diet high in fruit juices, sugar-sweetened beverages, refined grains, potatoes, And sweets/sweets are associated with increased risk of chronic disease. Yet little research has been conducted to determine the environmental impacts of these dietary practices, such as greenhouse gas emissions, use of high-quality cropland, nitrogen from fertilizers, and irrigation water.
Using data from the Nurses’ Health Study II, researchers analyzed the dietary intake of more than 65,000 eligible participants and examined their dietary associations with health outcomes, including relative risk of cardiovascular disease and environmental influences. To distinguish plant-based dietary patterns, the researchers characterized the participants’ diets using a variety of dietary indices, including healthy and unhealthy plant-based diet indices. Higher scores on the Unhealthy Plant-Based Diet Index indicate higher consumption of refined grains, sugary drinks, fruit juice, potatoes, and sweets/confectionery; While higher scores on the Healthy Plant-Based Diet Index indicate higher consumption of vegetables, fruits, whole grains, nuts, legumes, vegetable oils, and tea/coffee.
Participants who consumed a healthy plant-based diet had a lower risk of cardiovascular disease, and those diets had lower greenhouse gas emissions and use of cropland, irrigation water, and nitrogen fertilizers than those who ate unhealthy plant-based and animal-based diets. Participants who ate an unhealthy plant-based diet experienced a higher risk of cardiovascular disease and their diet required more cropland and fertilizer than healthy plant-based and animal-based diets. The findings reinforce previous studies showing that diets high in animal-based foods, particularly red and processed meat, have a greater environmental impact than plant-based diets.
“Because human health ultimately depends on the health of the planet, future U.S. Dietary Guidelines should include careful consideration of environmental sustainability and recognize that not all plant-based diets provide the same health and environmental benefits,” said Daniel Wang, assistant professor of nutrition. . at Harvard Chan School, Channing Department of Network Medicine at Brigham and Women’s Hospital and Harvard Medical School and co-authored the study.
This research was supported by the National Institutes of Health (NIH grants U01 CA176726, UM1 CA186107, HL35464, and 2T32CA057711).