April 8, 2011 -- Vegetarians have a reputation for being ''heart healthy.'' However, a new report says some vegetarians may be increasing their risk of heart problems from nutritional deficiencies in their diets.
Overall, meat eaters are still at higher risk of heart attacks and strokes compared to vegetarians, says researcher Duo Li, a professor of nutrition at Zhejiang University in Hangzhou, China.
But in his review of published articles from medical journals, he found that vegetarian diets are often lacking in some key nutrients. These include vitamin B12 and omega-3 fatty acids. The deficiencies were especially evident, he says, in vegans. Vegans don't eat meat, fish, or any kind of animal product, including eggs and milk.
The deficiencies in B12 and omega-3, in turn, are linked with higher blood levels of an amino acid called homocysteine. The deficiencies are also linked with decreased levels of HDL cholesterol, the so-called good cholesterol, he says. High homocysteine levels have been suggested as a risk factor for heart disease. Higher HDL levels are heart protective.
However, other nutrition experts say many vegetarians are already aware of the need to pay close attention to intake of vitamin B12 and omega-3s. They say the increased risk to heart health that Li suggests is only a hypothesis.
The study is published in the Journal of Agricultural and Food Chemistry.
Vegetarians, Vegans, and Heart Health
Li scanned the medical literature to study vegetarian diets and their effects.
His advice? "Vegans or vegetarians should try to healthfully increase their B12 intake by regularly eating seaweed [popular in China] or fortified cereals," he says.
For a boost in omega-3s, he suggests plant oils such as flaxseed.
Vegetarians and Heart Health: Perspective
Two nutrition experts who reviewed the study put the findings in perspective.
The link between the deficiencies in vitamin B12 and omega-3 fatty acids and a higher heart disease risk is only a hypothesis at this point, says Lona Sandon, RD, a spokewoman for the American Dietetic Association and assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center, Dallas.
"The majority of research on vegetarianism supports it as a heart health-promoting lifestyle," she says. The author carefully chooses the word 'may' [to suggest risk linked with the deficiencies] as there is little evidence to support his hypothesis at this time."
She does agree that vegetarians are often low in vitamin B12 and omega-3.
Her advice? ''If you choose to follow a vegetarian or vegan diet, plan wisely. Some thought needs to be put into planning balanced meals and a variety of foods as well as cooking methods to obtain all nutrients needed for optimal health."
Most vegetarians are aware of the need to pay attention to B12 and omega-3 fatty acids, says Reed Mangels, PhD, RD, the nutrition advisor for the Vegetarian Resource Group.
She suggests for vitamin B12 that vegetarians consider taking a supplement or eat cereals fortified with the vitamin or drink soy, rice, or almond milk.
Vegetarians who eat eggs and drink cow's milk, the so-called ovo-lacto vegetarians, can obtain their B12 from those foods, says Mangels, who has written a book for dietitians, The Dietitian's Guide to Vegetarian Diets.
Omega-3 fatty acids are found in flaxseed, walnuts, and soy products.
According to the Institute of Medicine, adults should take in about 2.4 micrograms daily of vitamin B12. Men should eat 1.6 grams of omega-3s daily; women, 1.1 grams.
About 3% of the U.S. population is vegetarian, Mangels says. About one-third eat no meat but do eat eggs and dairy. Another one-third are vegans, who eat no dairy products. Another one-third eat no animal products, but do eat honey.