Garlic benefits health, UAB researchers say

A few cloves of garlic may put the “Bam!” in a good pesto, but this famed spice can also prevent “Bam!” from occurring in the cardiovascular system. Thanks to the work of UAB scientists, the process by which garlic imparts protection against high blood pressure and cardiovascular disease is now known.

“Science is catching up with what native peoples have known for centuries,” says David Kraus, associate professor in the departments of environmental health sciences and biology, “namely, that garlic can impart positive effects on a person’s health. We have received calls from all over the world in response to this study. People are very excited about the health benefits of garlic consumption.”

Gloria Benavides, an American Heart Association postdoctoral fellow also in the department of environmental health sciences, Kraus and their colleagues found that red blood cells could metabolize sulfur compounds contained in garlic and, in turn, liberate hydrogen sulfide (H2S), an endogenously produced anti-oxidant, into the bloodstream. In order to sustain life, tissues likely require low concentrations of H2S; high concentrations of H2S as a gas, however, are actually toxic.

“Organisms across many biological phyla produce hydrogen sulfide,” Kraus says. “Its production following metabolism of the poly-sulfur compounds in garlic boosts concentrations just enough to enhance its protective properties. A fine line exists between its protective versus toxic concentrations.”

Interestingly, the number of sulfur atoms comprising the garlic compounds dictated the amount of H2S produced.

“Most of these garlic compounds contain two or three sulfurs but can have up to five or six sulfur atoms,” says Kraus. “We found that the higher number of sulfur atoms, the more effective was the compound at producing hydrogen sulfide.”

The investigators were also able to demonstrate this physiological response in an aorta that was submerged in an organ bath. The tension produced by the blood vessel held open with metal hooks was measured with a strain gauge. When H2S was produced the vessel relaxes and once the H2S was used up, the vessel would then reconstrict.

“The readout from these experiments is that H2S released upon break-down of the garlic compounds causes blood vessels to relax,” Kraus says.

The results obtained by UAB investigators corroborate studies conducted by colleagues John Elrod and David Lefer and others at the Albert Einstein College of Medicine. These scientists simulated a heart attack in mice by clamping off blood flow to the heart. After 30 minutes, the clamp was released so that blood flow could return. This reperfusion of blood caused extensive damage to the heart tissue. If H2S was present, however, tissue damage was avoided.

“Hydrogen sulfide protects against cell and tissue damage from heart attacks,” says Jeannette Doeller, associate professor of Environmental Health Sciences at UAB and a co-author of the recent UAB findings.

Each day, cells in the body are victims of oxidative stress, caused by such molecules as reactive oxygen species and peroxides. As people age, the effects of oxidative stress increase because the body loses its ability to counteract the effect. Alzheimer’s disease and cardiovascular disease are only two of the many ailments that have been linked to oxidative stress. Even the immune system releases hydrogen peroxide in response to a wound; although this reaction is necessary to protect from bacterial infections, it still contributes to tissue damage. H2S may very well be the anti-oxidant needed to counteract oxidative stress.

Previous work performed in the laboratory of Mark Roth at the Fred Hutchinson Cancer Research Center in Washington has demonstrated that H2S even has the ability to induce a state of suspended animation in mice in which, essentially, their life is put on hold for an unspecified amount of time. This is, once again, another enormous feat for H2S.

“When tissue is in suspended animation, the demand for oxygen decreases,” says Kraus. “Under normal situations, 70% of donated organs die before reaching the patient in need. We can eventually stop this and lengthen the amount of time an organ is viable.”

“H2S seems to have numerous medical applications,” says Kraus. “It has the potential to protect cells and tissues during general surgery, in cases of trauma, heart attacks, and battlefield wounds. In fact, I would not be surprised if one day it is standard practice to have it available in ambulances so that it can be quickly dispensed to heart attack victims in an effort to prevent tissue damage.”

According to Doeller, the mediator of garlic’s good health benefits is H2S. Many garlic compounds have been isolated and proven to be effective, but it is this common metabolite that imparts its beneficial properties. These studies may actually lead to improvements in garlic supplements, as the effectiveness to date has been inconsistent.

“This is an exciting time for H2S research,” Doeller says. “Garlic has been known for centuries to have beneficial effects, and we encourage people to enjoy a garlic-rich diet.”

UAB graduate student Chris Chapleau couldn’t agree more.

“I found the results of these studies about garlic to be quite interesting,” he says. “I have always been a big fan of garlic, now I have even more reason to pile it on!”

Published in the UAB Kaleidoscope on October 23, 2007