TUESDAY October 16, 2007 (Foodconsumer.org) -- Eating garlic helps lower high blood pressure and protect against cardiovascular disease, according to a new study published in the journal Proceedings of the National Academy of Sciences (PNAS).

The study by researchers from the University of Alabama at Birmingham (UAB) showed the protective effect is determined by the amount of hydrogen sulfide (H2S) produced from garlic compounds when they interact with red blood cells in the body.

The UAB researchers found the released H2S led to relaxation of blood vessels, lowering the blood pressure and in rats the resulting H2S caused up to 72 percent relaxation of arteries.   For humans, the effective dose is two cloves a day.

Early studies have showed that garlic provides protection against a myriad health conditions including diabetes and cancer.

The current study by David Kraus, Ph.D., professor in the Department of Environmental Health Sciences and Biology and colleagues was meant to reveal the blood-pressure lowering and heart-protective effect of compounds from garlic known as polysulfides.

The study is believed to be the first to show garlic-derived polysulfides in the diet boost bodily H2S production.

“When these garlic compounds are metabolized to H2S in the vascular system, the H2S targets membrane channels and causes smooth muscle cells to relax,” Kraus said. “So a garlic-rich diet has many good effects, and H2S may be the common mediator.”

An early study by John Elrod and David Lefer, Ph.D., of the Albert Einstein College of Medicine published in PNAS that also showed H2S protected hearts from the tissue and cell damage often seen in patients who experienced in heart attack.

Kraus was cited as saying how hydrogen sulfide works to offer the protective effect is not entirely clear, but speculating that it limits oxidative damage to the cells. H2S, typical of the smell of rotten eggs, is a reducing agent that can neutralize some oxidative reactions.

“The role of garlic compounds in preventing platelet aggregation, which can trigger a heart attack or stroke, and in limiting cancer growth and the progression of several diseases is well documented,” Kraus said.

Further research is needed to understand how the garlic polysulfides work to relax the blood vessels.

A scientist affiliated with foodconsumer.org who was not part of the research team said that the relaxation of blood vessels by eating garlic is something that many people can experience.   Some men with cardiovascular problems may find them more active in bedroom after eating garlic.