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“When thinking about longevity, most of us would benefit from switching to a plant-based diet,” said Christopher Gardner, lead author of the new study and a nutrition scientist at Stanford University.
Gardner’s team found that transitioning to a plant-based diet can strengthen the heart in just eight weeks. During that time, participants lost weight and saw reductions in insulin and cholesterol levels that are linked to cardiovascular disease.
The findings add to the growing evidence that a vegan diet can benefit human health—and the environment.
How the Study Was Conducted
Researchers enlisted 22 pairs of healthy identical twins to control for genetic differences as well as variations in upbringing and lifestyle.
All participants followed what the team defined as a healthy diet throughout the study.
The volunteers’ meals included vegetables, legumes, fruits, whole grains, nuts, and seeds. One twin from each pair ate a strictly plant-based diet, while the other followed a diet that included a measured amount of meat determined by the research team.
“They dressed alike, spoke alike, and joked like people who spend a lot of time together,” Gardner said. But different processes were happening in the bodies of the two groups.
For the first four weeks, researchers provided specially prepared breakfasts, lunches, and dinners and gave strict instructions on what participants could and could not eat, with an emphasis on maintaining a balanced variety of foods. Volunteers were also forbidden from eating processed foods, according to Science Alert.
In the study’s second phase, participants continued the diet but shopped for groceries and prepared their own meals.
The Effects of the Experiments
Volunteers were allowed to eat as much as they wanted; the study set no calorie limits or weight-loss goals. Still, most participants lost excess weight.
All participants showed improvements on measures of cardiovascular health. The largest gains occurred in the twins who followed the strictly plant-based diet: their insulin levels dropped by about 20 percent, and their low-density lipoprotein cholesterol (LDL-C) levels fell. High LDL-C is a key risk factor for atherosclerosis, stroke, and heart disease.
The study also recorded the expected drop in vitamin B12 levels. Because the trial was short-term, that decline was not large.
Researchers advised people to transition to a plant-based diet “mindfully.” That shift can reduce intake of essential nutrients like vitamin B12, so new vegans are often advised to take supplements.
The team said veganism faces strong social resistance—”so strong that the word has even become a slur.” That resistance exists even though many people agree with the principles behind vegan and vegetarian diets.
Gardner added that, beyond the heart benefits seen in this study, a vegan diet can increase beneficial gut bacteria and protect telomeres, the ends of chromosomes that are linked to aging.
For those hesitant to switch to a fully vegan diet right away, the nutritionist recommended incorporating as many plant-based foods into meals as possible.
The results were published in JAMA Network Open.
