Eating a plant-based diet is good for your health, but not if those plant foods are highly processed, a new study finds.
The findings suggest that not all plant-based diets are the same, and that what producers do to plant foods before they reach your plate can have very different effects on your health.
A new study published Monday in The Lancet Regional Health Europe found that eating ultra-processed plant-based foods, such as meat substitutes, fruit juices and pastries, increases the risk of heart attack and stroke. But plant-based foods, such as fruits, vegetables, whole grains and nuts, which are minimally processed (washed, cut, packaged, etc.) and come in a more or less natural state, may offer a protective effect against cardiovascular disease.
“Ultra-processed foods have come under intense scrutiny from health authorities in recent years. What’s unusual about this new study is that it focuses specifically on the health effects of ultra-processed plant-based foods and compares them to minimally processed plant-based foods. Given that plant-based foods are generally healthy in their natural form, this study suggests that ultra-processing has unique detrimental properties that alter foods in ways that may harm human health in the long term.”
“The artificial and excessive flavors of these foods can make people dependent on them and make it difficult for them to enjoy the natural flavors of real foods like fruits and vegetables,” said Fernanda Lauber, a researcher at the Center for Nutrition and Health Epidemiology Research at the University of São Paulo in Brazil and lead author of the new study.
Ultra-processing distorts plant-based foods
The new study analysed data from 118,000 adults who were followed for nearly 10 years as part of UK Biobank, a study that has been tracking the health and lifestyle habits of people across the UK. As part of the long-term study, participants answered questions about their diet, habits and environment on various occasions, and provided biological samples, as well as health and medical records. Findings include:
The more ultra-processed foods you eat, the more likely you are to die from heart disease. For every 10% increase in calories from ultra-processed, plant-based foods, there is a 5% increase in the likelihood of developing cardiovascular disease, and a 6% increase in the risk of coronary heart disease in particular. For every 10% increase in the intake of non-ultra-processed, plant-based foods, participants were 8% less likely to develop coronary heart disease and 20% less likely to die from coronary heart disease. There was also a 13% lower risk of dying from cardiovascular disease.
Many of the foods studied were not what would typically be considered plant-based foods, but the main ingredients in many junk foods are plant-based, such as cane or beet sugar, flour, corn, potatoes, fruit juices, and vegetable oils.
Plant-based foods defined as ultra-processed in the new study include:
Wheat and corn: pastries, breads, biscuits, cakes, packaged breads, cereals, chips and savory snacks. Potatoes: french fries and potato chips. Beet, cane and other sugars: candy and soft drinks. Fruit and vegetables: sauces, dressings, juices, beverages and frozen pizza. Soy, wheat, beans and peas: meat substitutes including imitation burgers and imitation sausages.
Ultra-processed foods strip healthy nutrients and replace them with salt, sugar and fat, and destroy the internal structure of foods – the “food matrix” – so that our bodies absorb food more quickly, which can result in less satiety and in some cases higher blood sugar levels.
During industrial processing, foods are often subjected to extreme pressures and temperatures that can transform additives into harmful new compounds. Two well-known compounds produced during food processing, acrolein and acrylamide, have been shown to promote cardiovascular disease.
Plant-based foods that aren’t heavily processed contain fiber, polyphenols, plant sterols, and a variety of other compounds that reduce inflammation and promote overall health.
Lauber recommended eating mostly minimally processed foods and avoiding packaged foods that contain large amounts of additives such as dyes, sweeteners, flavors, emulsifiers and other substances that you probably wouldn’t find in your own kitchen.
“When buying pre-made or prepared foods, the best advice is to read the ingredients list,” Lauber says. “If it only contains ingredients you’re familiar with and have in your kitchen, it’s most likely made from real food and not heavily processed.”
Health risks of ultra-processed plant foods
Past research supports the findings about ultra-processed, plant-based foods. In one large-scale study published in 2022, scientists looked at the diets of 78,000 health-conscious Seventh-day Adventist men and women, many of whom were vegans or vegetarians. After following the participants for an average of about eight years, they found that those who ate the most ultra-processed foods had a 14% higher risk of death than those who ate the least.
Dozens of studies have linked ultra-processed foods to premature death, increased weight gain and an increased risk of more than 30 health conditions, including obesity, cancer, diabetes and heart disease. The committee that writes the federal government’s influential Dietary Guidelines for Americans is debating whether to include a warning against ultra-processed foods in the next version of the guidelines.
Ultra-processed foods are what scientists call hyper-palatable. They are industrially manufactured foods that contain an unusual combination of flavors and additives, including salt, sugar, stabilizers, emulsifiers, oils and artificial ingredients, that make us crave and overeat. In most cases, these foods are stripped of fiber, vitamins, minerals and other natural nutrients and are packed with calories.
The study authors cautioned that while the study showed a correlation between ultra-processed plant-based foods and cardiovascular disease, it does not prove causation: For example, participants may have misreported the types or amounts of food they ate, or other lifestyle factors could explain the findings.
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