According to a new study led by Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital, healthier plant-based dietary habits were associated with better environmental health, whereas less healthy plant-based dietary patterns, which are higher in foods like refined grains and sugar-sweetened beverages, required more cropland and fertiliser.
“The differences between plant-based diets were surprising because they’re often portrayed as universally healthy and good for the environment, but it’s more nuanced than that,” said Aviva Musicus, postdoctoral research fellow and corresponding author of the study in the Department of Nutrition at Harvard Chan School.
“To be clear, we are not claiming that less healthful plant-based diets are more harmful to the environment than animal-based diets. Our findings, however, suggest that plant-based diets can have varying health and environmental effects.” The study, one of the first to look at the health and environmental implications of diverse plant-based diets at the same time, was published in the November 2022 issue of The Lancet Planetary Health.
Previous study has shown that different plant-based diets have distinct health consequences. Plant-based diets high in whole grains, fruits, vegetables, nuts, legumes, vegetable oils, and tea/coffee, for example, are linked to a lower risk of chronic disease, whereas plant-based diets high in fruit juices, sugar-sweetened beverages,
However, insufficient study has been undertaken to establish the environmental consequences of various dietary practises, such as greenhouse gas emissions, usage of high-quality farmland, nitrogen from fertiliser, and irrigation water.
Using data from the Nurses’ Health Study II, the researchers assessed the food intakes of almost 65,000 qualified individuals, as well as the connections between their diets and health outcomes, including relative risks of cardiovascular disease, and environmental repercussions. The researchers used numerous dietary indicators, including the Healthy and Unhealthy Plant-based Diet Indices, to assess individuals’ diets in order to discern plant-based dietary patterns.
Higher scores on the unhealthy plant-based diet index indicated increased consumption of refined grains, sugary drinks, fruit juice, potatoes, and sweets/desserts, whereas higher scores on the healthy plant-based diet index indicated increased consumption of vegetables, fruits, whole grains, nuts, legumes, vegetable oils, and tea/coffee.
Participants who had healthy plant-based diets had a decreased risk of cardiovascular disease, and their diets used less farmland, irrigation water, and nitrogenous fertiliser than those who consumed harmful plant-based and animal-based meals. Participants who consumed bad plant-based diets had an increased risk of cardiovascular disease, and their diets necessitated more farmland and fertiliser than diets rich in healthy plant-based and animal foods.
The findings also supported previous research suggesting that diets heavy in animal-based foods, particularly red and processed meat, have a more negative environmental impact than plant-based diets.
“Because human health ultimately depends on planetary health, future US dietary guidelines should include nuanced consideration of environmental sustainability and recognise that not all plant-based diets confer the same health and environmental benefits,” said Daniel Wang, assistant professor in the Department of Nutrition at Harvard Chan School, the Channing Division of Network Medicine at Brigham and Women’s Hospital and Harvard Medical School, and co-author of the study.