Garlic lovers, take heart: The pungent root may promote healthier responses in blood vessels.
So say researchers who found that compounds in garlic cause tissues or blood vessels to release a chemical called hydrogen sulfide. In large quantities, this compound can be deadly, but it's also an essential molecule within the body, causing blood vessels to relax and reducing dangerous inflammation.
But how you take your garlic matters, the research showed. "If you prepare it in certain ways, you can lose the compounds that cause it to release hydrogen sulfide, so that helps explain why there has been such great variability in studies," noted senior researcher David Kraus, an associate professor of environmental health sciences at the University of Alabama, Birmingham.
His team published its findings in this week's online edition of the Proceedings of the National Academy of Sciences.
Not all research positive
In the array of garlic health studies, more than half have shown some positive effect, but that effect has tended to be small, and some trials have even shown negative health effects, Kraus noted. Some of his team's experiments used juice extracted from supermarket garlic. Human red blood cells exposed to tiny amounts of the juice began emitting hydrogen sulfide. Most hydrogen sulfide production took place at the membrane of the red blood cells, although a fraction was made within the cells.
Other studies of garlic's health effects have failed, Kraus said, because they look for activity that is impossible - a reduction in blood cholesterol levels, for example.
Another expert urged caution in interpreting the Birmingham team's results.
Eric Block, professor of chemistry at the State University of New York, Albany, has also done extensive work on garlic. He called the paper "provocative", but expressed some concerns.
For example, he said, "the benefits of garlic on cardiovascular disease remain controversial, because they have not been established by the gold standard method of placebo-controlled, double-blind clinical studies," he said.
10 cloves of garlic a day
It's also uncertain that garlic's purported beneficial effects are due to the mechanism described in the new report, Block added. Clinical trials are needed to help prove that point, he said.
According to Block, Kraus' team, "should be more conservative in over-extending some of their conclusions in the absence of additional work." However, "their work does represent a significant advance in the science of this amazing, ancient, ever-popular herb," he said.
Kraus stressed that his study only looked at the effect of fresh garlic, not garlic supplements. "What we are proposing is that you eat a garlic-rich diet," he said. "We haven't really tried to look at supplements yet."
"Garlic-rich" has different meanings, depending on the part of the world being studied, Kraus added. "In the Middle East, that would be five to 10 cloves of garlic a day," he said. "If you go to the Far East, it would be even higher." - (Ed Edelson/HealthDay)
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