If you’re at high risk of cardiovascular disease (CVD)—as so many of us are—a vegetarian diet may be just what the doctor should order, suggest the findings of a new meta-analysis in JAMA Network Open.
Researchers evaluated 20 randomized controlled trials (the gold standard of studies) that included a total of 1,878 participants ages 28 to 64 with or at elevated risk of CVD, who ate either a plant-based diet for two to 24 months (six months on average) or a control diet. The control diets ranged from high-protein omnivorous diets to standard weight-loss and diabetic diets to the DASH diet (used primarily to lower blood pressure).
Those in the vegetarian groups had significant reductions in several cardiometabolic risk factors, namely LDL (“bad”) cholesterol, hemoglobin A1C (a measure of long-term blood sugar control), and body weight, compared to the control diets, after adjusting for calorie intake, physical activity, and medication use. The greatest improvements in LDL and A1C were seen in those with diabetes as well as those at high risk of CVD.
Another positive outcome: Most participants were on medications to control their cholesterol, blood sugar, or blood pressure, but eight of the trials reported decreases in the doses needed due to the effects of the vegetarian diets. That is, the benefit of vegetarian diets went beyond standard drug therapy.
No changes were seen in systolic blood pressure, however, leading the researchers to conclude that diet quality plays a major role in lowering blood pressure independent of animal food consumption. Studies of the DASH diet—which allows for some animal products, particularly dairy—have previously been shown to have a beneficial effect on blood pressure.
The studies included in the meta-analysis were from the U.S., Europe, Asia, and New Zealand, published between 1990 and 2021. The vegetarian diets tested were mostly vegan (no animal products at all), followed by lacto-ovo diets (which exclude all meat but include dairy and eggs), and lacto-vegetarian diets (dairy, no eggs). Three trials assigned participants to the strict Ornish Diet, which excludes meat and allows for only nonfat dairy and egg whites.
Cardiovascular disease remains a leading cause of death worldwide. Health organizations such as the American Heart Association have long recommended diets that are rich in plant foods, and prior studies, both randomized and observational, have shown their merits in preventing cardiovascular disease. The authors of the new study say their research is the first meta-analysis of randomized controlled trials to include people who already have CVD.
Well-balanced vegetarian and vegan diets may benefit the cardiovascular system by supplying lower amounts of saturated fat and possibly other atherogenic substances. Such diets are also high in heart-healthy fiber, sterols, unsaturated fats, potassium, magnesium, and phytochemicals and are generally lower in calories.
Still, keep in mind that not all vegetarian/vegan diets are healthful. Especially when followed for convenience or ethical reasons, they may contain lots of ultraprocessed foods, fried foods, refined carbs, empty sugar calories, artificial sweeteners, and salt. If you follow or plan to follow a more plant-based diet for your heart health or otherwise, be sure to focus on unprocessed or minimally processed foods prepared in healthful ways.
