7 Healthcast: Garlic and blood flow

"Garlic has allicin in it, which when metabolized creates hydrogen sulfide, and that is what seems to have the effect on the blood vessels," said Registered Dietician Melanie Pearsall of Mass General Hospital for Children.

Researchers studied the effects of juice extracted from store-bought garlic on red blood cells. They found as soon as garlic interacted with red blood cells in the lab there was an increased production of hydrogen sulfide, a byproduct that relaxes blood vessels and improves circulation.

But Pearsall warns that while adding garlic to your diet may be beneficial, taking garlic supplements may not.

"I would say that's a real leap, because supplements, at least right now, are not regulated," Pearsall said. "So the active ingredient or component in those supplements would really need to be standardized for there to be some kind of outcome that we could really look at and say 'Wow, these supplements really work.'"

Another concern with taking supplements is that they can interact with medication. For example, garlic supplements may interfere with blood thinning medicine; so if you're thinking about taking any over the counter supplement, talk with your doctor first.

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