“Most of the difference in risk is probably caused by effects on cholesterol and blood pressure, and shows the important role of diet in the prevention of heart disease,” lead researcher Dr. Francesca Crowe, of the cancer epidemiology unit at the University of Oxford, said in a university news release.
The study included nearly 45,000 people from England and Scotland, about a third of who were vegetarians. According to the research team, having such a large proportion of vegetarians in this type of study is rare and enabled a more precise comparison of heart disease risk between vegetarians and non-vegetarians.
The participants were recruited to the study throughout the 1990s, and all of them provided information about their health and lifestyle when they joined. About 20,000 of the volunteers also had their blood pressure and cholesterol levels checked, and follow-up continued until 2009.
During the follow-up period, heart disease was identified in more than 1,200 people, including 169 deaths from heart disease.
Crowe’s team found that the vegetarians had a 32 percent lower chance of being hospitalized or dying from heart disease versus people who ate meat or fish. The vegetarians typically had lower blood pressures and cholesterol levels than non-vegetarians.
Vegetarians also tended to be slimmer and there were fewer cases of diabetes, but these two factors were not found to significantly affect the study results, the researchers reported in the January issue of the American Journal of Clinical Nutrition.
Still, the study could only show an association between a meat-free diet and better heart health, not a cause-and-effect link. And one U.S. expert said the research did have some limitations.
First of all, the vegetarians in the study “were roughly 10 years younger [on average] than nonvegetarians,” possibly skewing the results, said Dr. Stephen Green, associate chairman of the department of cardiology at North Shore University Hospital, in Manhasset, N.Y. He also believes that the populations studied may not be equivalent to the average American.
“These people are much thinner than Americans, smoke less and are more active,” Green noted. “With respect to this study, the average BMI [body-mass index, a measure of weight vs. height] in this study is between 23 and 24, an increasingly rare number for Americans. For instance, this would be 6 foot tall, 173 pounds or 5 foot 3 inches and 132 pounds. These sort of weights are becoming increasingly uncommon in America.”
But another expert said the health benefits of vegetarianism are well-established.
“‘Eat your veggies!’ is a favorite saying of mothers everywhere. Now that same quote may be the best advice as you leave your cardiologist’s office in search of advice to reduce the risk of a heart attack,” said Dr. Kevin Marzo, chief of cardiology at Winthrop-University Hospital, in Mineola, NY.
Marzo also wondered about the effect on heart health of diets where meat and fish are lowered but not eliminated.
“Though not addressed in this important study, for those not ready for a meat-free diet, pesco-vegetarians (fish) and semi-vegetarians who limit animal products but still eat meat once or week or so, may have ‘intermediate protection’ against heart disease,” he said.