May 30, 2023 – Compared to meat eaters, people who followed a vegan or vegetarian diet had lower levels of certain fats in their blood that can block arteries and possibly lead to heart disease and stroke, new research shows.
The findings – published May 24 in the European Heart Journal – are from a meta-analysis (a study that grouped all the results from smaller studies) of 30 generally short, small, randomized controlled trials published between 1982 and 2022.
In the individual studies, researchers randomly assigned some people to continue eating an omnivore diet (meat, dairy, and plants), and assigned other people to either a vegan diet or a vegetarian diet – for about 7 months on average.
At the end of this time, those who ate a plant-based diet had lower levels of some blood fats than people who ate an omnivore diet.
Specifically, they had 7% lower total cholesterol, 10% lower low-density lipoprotein (LDL) cholesterol (or "bad" cholesterol), and 14% lower apolipoprotein B (apoB) levels.
ApoB is the main protein found in LDL cholesterol and can be used as another sign of cardiovascular disease.
There was no significant difference in triglycerides, another type of fat linked to heart attacks and strokes at high levels.
“Vegetarian and vegan diets were associated with a 14% reduction in all artery-clogging lipoproteins as indicated by apolipoprotein B," senior author Ruth Frikke-Schmidt, MD, PhD, with the University of Copenhagen, said in a news release.
"This corresponds to a third of the effect of taking cholesterol-lowering medications such as statins," she said, "and would result in a 7% reduction in the risk of cardiovascular disease in someone who maintained a plant-based diet for five years."
Combining statins with plant-based diets would likely produce a greater (synergistic) effect, she speculated.
Importantly, the findings were similar for people of different ages, body mass index, and states of health, living in different continents.
“If people start eating vegetarian or vegan diets from an early age," Frikke-Schmidt said, "the potential for reducing the risk of cardiovascular disease caused by blocked arteries is substantial."
In addition, recent studies have shown that if the populations of high-income countries shift to plant-based diets, this can reduce net emissions of greenhouse gases by between 35% and 49%, she noted.
Not All Plant-Based Diets Are Equal
In an editorial, Kevin C. Maki, PhD, of Indiana University, and Carol Kirkpatrick, MPH, PhD, of Idaho State University, wrote that the new study adds evidence supporting healthy vegan and vegetarian diets to potentially reduce the risk of heart disease and stroke.
"While it is not necessary to entirely omit foods such as meat, poultry, and fish/seafood to follow a recommended dietary pattern," they noted, "reducing consumption of such foods is a reasonable option for those who prefer to do so."
Other experts who were not involved with this research agree, according to comments they gave to the U.K. Science Media Center.
"Although a vegetarian and vegan diet can be very healthy and beneficial with respect to cardiovascular risk, it is important that it is well planned so that nutrients it can be low in are included, including iron, iodine, vitamin B12 and vitamin D," said Duane Mellor, PhD, with Aston University in Birmingham, U.K.
Some people "may find it easier to follow a Mediterranean-style diet that features plenty of fruit, vegetables, pulses, wholegrains, fish, eggs and low fat dairy, with only small amounts of meat," said Tracy Parker, a heart health dietitian with the British Heart Foundation in London.
"There is considerable evidence that this type of diet can help lower your risk of developing heart and circulatory diseases by improving cholesterol and blood pressure levels, reducing inflammation, and controlling blood glucose levels," she said.
Aedin Cassidy, PhD, at Queen’s University in Belfast, U.K., noted that "not all plant-based diets are equal." She said that healthy ones, marked by fruits, vegetables, and whole grains, improve health, but "other plant diets (e.g. those including refined carbohydrates, processed foods high in fat/salt etc.)" do not.
This well-done analysis of 30 clinical trials involved more than 2,000 people, and it "highlights the value of a vegetarian diet in reducing the risk of a heart attack or stroke through reduction in blood cholesterol levels," said Robert Storey, MD, at the University of Sheffield, U.K.
But "people inherit the tendency for their livers to produce too much cholesterol, meaning that high cholesterol is more strongly influenced by our genes (DNA) than by our diet," he said.
"This explains why statins are needed to block cholesterol production in people who are at higher risk of, or have already suffered from, a heart attack, stroke or other illness related to cholesterol build-up in blood vessels.”
"Plant-based diets are key instruments for changing food production to more environmentally sustainable forms, while at the same time reducing the burden of cardiovascular disease" in an aging population, Frikke-Schmidt said.
"We should be eating a varied, plant-rich diet, not too much, and quenching our thirst with water.”