Garlic Raises Hydrogen Sulfide Levels, Relaxing Arteries

A new study has found that the protective effect of garlic is closely linked to how much hydrogen sulfide (H2S) is produced from garlic compounds interacting with red blood cells (RBCs).

Researchers from the University of Alabama at Birmingham (UAB, USA) examined molecules in garlic called polysulfides and their ability to liberate H2S within cells. They found that when fresh garlic was used at a concentration equal to eating two cloves, the interaction triggered RBCs to release H2S. This H2S production is supported by glucose-maintained cytosolic glutathione levels and is to a large extent reliant on reduced thiols in or on the RBC membrane.

The resulting increase in H2S production caused up to 72% vessel relaxation in rat arteries. The researchers found that H2S production from organic polysulfides was facilitated by allyl substituents and by increasing numbers of tethering sulfur atoms. The findings were published in the October 19, 2007, online edition of the journal Proceedings of the National Academy of Sciences (PNAS).

"When these garlic compounds are metabolized to H2S in the vascular system, the H2S targets membrane channels and causes smooth muscle cells to relax,” said lead author said David Kraus, Ph.D., an associate professor in the departments of environmental health sciences and biology. "So a garlic-rich diet has many good effects, and H2S may be the common mediator.”

H2S is a toxic, flammable gas responsible for the smell of rotten eggs. It's also produced naturally by the body in small amounts, and as age advances, H2S production dwindles. Exactly how H2S affords the cardiovascular system so much protection is not entirely clear.


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