Plant-based diets are not universally healthy and environmentally sustainable, according to a new study. Harvard researchers found significant differences in the health and environmental outcomes between different types of plant-based foods, writes Jack Thompson.
Healthy plant-based food is more sustainable, the experts discovered, in what they claim is one of the first studies to simultaneously analyse the environmental and health benefits of plant-based diets.
Participants who ate plant-based foods such as fruit and vegetables, nuts, whole grains and legumes had a lower risk of heart and chronic diseases than those who consumed sugary drinks, refined grains, sweets and potatoes. The healthier plant-based diets also required less cropland and fertiliser.
“The differences between plant-based diets was surprising because they’re often portrayed as universally healthy and good for the environment, but it’s more nuanced than that,” said author of the study Aviva Musicus, postdoctoral research fellow in the department of nutrition at Harvard.
The research used data from 90,844 participants’ diets to determine cardiovascular and chronic disease risk and correlated this with a study of 65,625 people on the environmental impacts of food items, using greenhouse gases, land-use, fertiliser and irrigation water as metrics.
Despite the differences in environmental and health impacts of plant-based diets, researchers reinforced that animal-based foods, especially red and processed meats, had the highest environmental impacts across the metrics measured.
“To be clear, we’re 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,” Musicus added.
US dietary guidelines should include “nuanced consideration of environmental sustainability”, the researchers noted in their paper published in The Lancet Planetary Health.
Last year, the UK government’s Scientific Advisory Committee on Nutrition (SACN) began considering whether (and how) to make sustainability a factor in the nation’s diet, alongside elements such as 5-a-day. “While adherence to UK dietary recommendations is estimated to reduce emissions by 30%, healthier products or diets do not always have a lower environmental impact,” noted committee papers which were reported by The Grocer.
This followed Henry Dimbleby’s recommendations in his National Food Strategy report for major changes to the UK’s diet, including eating 30% less meat. The government has since resisted implementing any policies to reduce meat consumption, which has landed it with a court battle.
Research led by the Oxford Martin School published in 2020 concluded that national guidelines “could be both healthier and more sustainable”.
