Plant-based diets have long been praised for their fiber and important nutrients, but the new study shows that these benefits fade when such diets are based on ultra-processed foods, which often contain preservatives, fats, and added sugar.
The study followed more than 63,800 middle-aged adults in France for over nine years. The results showed that those who followed a completely plant-based, unprocessed diet were 44% less likely to develop coronary heart disease compared to others.
Conversely, a vegetarian diet that relied heavily on ultra-processed foods increased the risk of coronary heart disease by 46% and cardiovascular disease in general by 38%. These participants tended to consume supermarket bread, ready-made pasta dishes, canned soups, and ready-made salads with heavy dressings.
"Our results show that reducing consumption of animal products alone is not enough, but we must also focus on eating unprocessed plant foods to maintain heart health," said Clementine Brio, the lead researcher on the study, from Sorbonne University.
The researchers pointed out that food quality and processing methods are more important than whether it is plant-based or animal-based. People who consumed some animal products and avoided ultra-processed foods were no more likely to develop heart disease than those who followed a healthy, plant-based diet rich in whole foods.
The data was based on the French NutriNet–Santé study, which periodically recorded participants' diets using detailed food logs, taking into account factors such as smoking, physical activity, and other lifestyle factors. Foods were also categorized by degree of processing using the NOVA system, which distinguishes between unprocessed, minimally processed, highly processed, and ultra-processed foods.
Experts recommended reducing the consumption of ultra-processed foods, whether plant-based or animal-based, and focusing on fresh, whole foods, along with a healthy lifestyle that includes physical activity and avoiding smoking, to reduce the risk of heart disease and other cardiovascular diseases.
The study was published in the journal "The Lancet".
