Many earlier studies have suggested that eating a large amount of ultra-processed foods is linked to an increased likelihood of developing cardiovascular disease. At the same time, other research has shown that diets rich in plant-based foods, when of good nutritional quality, may help lower this risk. However, simply labelling a diet as “plant-based” does not always mean it is healthy, because plant-derived foods can vary widely in how they are prepared and processed. A diet full of vegetables, whole grains, legumes, fruits, nuts, and seeds in their natural or lightly processed forms is not the same as a diet high in packaged snacks, sweetened drinks, and ready-made meals, even if all of these are technically made from plants. As plant-based eating becomes more popular, it has become increasingly important to understand what “plant-based” really means in practice, and how different types of plant-derived foods affect the body.
A team of researchers from INRAE, Inserm, Université Sorbonne Paris Nord, and Cnam examined this question in depth by analysing not only whether people ate more plant-based or animal-based foods, but also the nutritional value of the foods and the level of industrial processing involved. Nutritional quality refers to how foods are composed in terms of fat, sugar, salt, fibre, and key vitamins and minerals. The level of processing, on the other hand, refers to how much the food has been altered from its original form through factory preparation, use of additives, or refinement. By combining these two considerations—quality and processing—the researchers were able to gain a clearer picture of how modern dietary patterns relate to heart health, beyond simple categories such as vegetarian, vegan, or omnivorous.
To conduct this research, the scientists used data from 63,835 adults participating in the long-running NutriNet-Santé study in France. The participants’ diets were recorded through detailed online questionnaires that documented their food and drink consumption over several days. The average follow-up period for monitoring their health outcomes was just over 9 years. For some individuals, the study followed their dietary patterns and cardiovascular health for up to 15 years. With this information, the researchers identified different types of diets not only by the proportion of plant-based versus animal-based foods, but also by the nutritional value of those foods and the degree of processing before consumption.
The results showed that individuals who consumed a high proportion of plant-based foods that were both nutritionally balanced and minimally processed had a significantly lower risk of developing cardiovascular diseases. Specifically, those whose diets emphasised fresh or lightly processed plant foods—such as vegetables, whole fruits, whole grains, legumes, and nuts—had roughly a 40 per cent lower risk of heart disease compared with people whose diets contained fewer such foods and more animal-based products. These findings support existing public health guidance encouraging diets built around whole plant foods that are rich in fibre, antioxidants, and healthy fats, while being relatively low in added sugars, salt, and saturated fats.
However, the study also revealed that eating a diet high in plant-based foods does not automatically offer protection if those foods are ultra-processed. Individuals who ate substantial amounts of plant-based foods that underwent extensive industrial processing did not experience a reduced risk of cardiovascular disease, even when these products appeared nutritionally acceptable on labels. Examples of such foods include pre-packaged soups, industrial breads, ready-made meals, and salads prepared with processed dressings. Ultra-processed foods often contain additives, refined ingredients, and altered food structures that may affect metabolism, digestion, and appetite regulation. This means that, in theory, a plant-based diet may still act in the body in ways that do not support heart health if the foods have been heavily processed during manufacturing.
The study further found that diets high in plant-based foods, both low in nutritional quality and ultra-processed, were associated with an increased risk of cardiovascular disease. This category included sugary cereals, sweetened drinks made from plant extracts, confectionery, flavoured snack foods, and similar items. In these cases, the risk of heart disease increased by about 40 per cent when compared with people consuming minimally processed, nutrient-rich plant foods. These findings highlight an important point for public health messaging: encouraging plant-based eating is beneficial only when the foods promoted are genuinely nutritious and as close as possible to their natural forms. For dietary guidance to be practical, it must consider not only the plant-to-animal ratio in the diet but also the nutritional composition and degree of processing of the foods consumed.
More information: Clémentine Prioux et al, Cardiovascular disease risk and the balance between animal-based and plant-based foods, nutritional quality, and food processing level in the French NutriNet-Santé cohort: a longitudinal observational study, The Lancet. DOI: 10.1016/j.lanepe.2025.101470
Journal information: The Lancet Provided by INRAE – National Research Institute for Agriculture, Food and Environment
