Bloomberg — Garlic, the pungent bulb used for centuries in cooking and healing, may help protect against heart disease by relaxing arteries and increasing blood flow, scientists said yesterday.

Red blood cells make components of garlic into hydrogen sulfide, a biological messenger that stimulates vessels to open, according to a laboratory study that will be published this week in the journal Proceedings of the National Academy of Sciences.

Research published earlier this year showed that eating garlic daily didn't lower harmful cholesterol in people with moderately high levels of the fatty blood protein. By boosting hydrogen sulfide levels, garlic may promote heart health in other ways, said David Kraus, a University of Alabama at Birmingham biologist who led the blood-vessel study.

"Hydrogen sulfide opens blood vessels and is an antioxidant, which reduces damage to cells," Kraus said in a telephone interview on October 12. "That can help keep a sufficient flow of blood to organs."

More studies are needed to confirm that the chemical observations translate into better human health, said Eric Block, a State University of New York at Albany biochemist who helped write the study of garlic and cholesterol.

"The benefits of garlic on cardiovascular disease remain controversial since they have not been rigorously established by the gold standard method of placebo-controlled double-blind clinical trials," he said yesterday in an e-mail.

Garlic has also been shown to have antibiotic effects, according to the NIH website. Those may contribute as much to heart health as blood-vessel relaxation, said Christopher Gardner, a Stanford University assistant professor of medicine in California who collaborated with Block on the cholesterol research.

"It's fabulous that they found this potential mechanism" in the test-tube experiments, he said today in a telephone interview, "but there's a huge leap of faith here that this same effect operates in humans."

Early research has also indicated that garlic, a member of a family of plants that includes lilies, may slow hardening of the arteries that often occurs with age, according to the US National Center for Complementary Therapy and Alternative Medicine.

The agency, a branch of the Bethesda, Maryland-based National Institutes of Health, is supporting studies to see how garlic interacts with drugs and whether it prevents harmful clotting, according to the NIH website.

The study was supported by the NIH and the Dallas-based American Heart Association.

Statistics suggest that people in countries such as Italy, China and Korea eat as many as eight to 12 cloves of garlic a day, which may protect them from heart disease, Kraus said. He said he eats several cloves daily himself.

"We chop up garlic and put it in hummus, drizzle it on salads, put it on meat and fish," he said. "It's not hard to do."