Garlic's power to ward off threats from vampires to infection has been passed down through the ages.

The herb -- in many different forms, including powders and freshly picked -- is credited with everything from treating skin conditions such as psoriasis to fighting cancer. CareFair.com and some beauty experts tout garlic for use on skin conditions -- even pimples -- but many dietitians said the research is inconclusive.

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The cancer claims are solid, according to research by the National Cancer Institute, which reported that "studies reveal that the benefits of garlic are not limited to a specific species, to a particular tissue or to a specific carcinogen."

Italian research published by the American Journal of Clinical Nutrition showed that adults who ate a half-cup of onions a day were about 65 percent less likely to develop cancer as those who shunned onions -- garlic eaters reduced their cancer risk by 30 percent.

However, it may be particularly good at fighting stomach and prostate cancers, though most of the research has happened in test tubes and still needs clinical trials, NCI said.

Fighting Fungus

Garlic has been used in cures for athlete's foot and yeast infections.

"Ajoene is an antifungal compound found in garlic," according to the skin treatments section of WebMD.com.

Doctors used it topically on the battlefields of both World Wars to fight gangrene after famed scientist Louis Pasteur noted that garlic seemed to have antibacterial properties.

Working In The Real World?

But a study published last month in the Archives of Internal Medicine said garlic stinks at reducing cholesterol and cast a shadow over what other powers garlic may have.

"Most of the medicinal claims about garlic revolve around the sulfur-containing substance allicin, which is produced when raw garlic is chopped or crushed," according to a news release from Stanford University, which led the study. "Allicin has been shown to inhibit the synthesis of cholesterol in test tubes and in animal models, but there is conflicting clinical evidence about its ability to react inside the human body the same way it does in a lab dish."

"The thing about garlic is that its compounds break down differently in your stomach (and) in your small intestine," said Anne Cundiff, a registered clinical dietitian at Creighton University, in Omaha, Neb. "Sometimes, the stomach acid will break it down."

That's why garlic may have shown promise in the test tube that didn't pan out in human trials. Stanford said its findings mean that all garlic-related claims need to be rigorously studied, in part because so much of the earlier research was funded by companies that have a commercial interest in the herb.

Benefits Despite Doubts

However, dietitians said that doesn't mean people should give up on garlic as part of a heart-healthy diet. Garlic has shown promise in stabilizing blood pressure, and it also keeps the intestinal tract working properly to guard overall health.

"Seventy-five percent of your immune system is in your intestinal tract," Cundiff said.

A clove or two a day in heart-healthy recipes is the dosage most people should aim for, Cundiff said. She hasn't altered that advice to her patients in light of the Stanford study.

"Garlic has vitamins A, C, potassium, amino acids, phosphorus -- it just is good for you on some level," she said.

Too Much Of A Good Thing

But don't overdo it, experts say. Eating more than two cloves of garlic a day will cause diarrhea in most people, and the same compound that gives garlic its potent scent will be released from the skin and sweat of people who overindulge.

In fact, Karen McWilliams, a registered dietitian at Bryan-LGH Hospital in Lincoln, Neb., said she's had to talk to patients who overdosed on garlic in their efforts to improve their cholesterol or cancer treatment.

"In our rehab unit, we have clients that were eating garlic every day, hoping it will change their cholesterol," McWilliams said, adding that she took complaints from other patients. "Other clients did not want to exercise close by (because of the smell)."

McWilliams said her best advice to clients is to "eat the rainbow" -- which means choosing a variety of foods and keeping the menu fresh.

"If people are so focused on garlic -- there are so many great fruits and vegetables out there to add to recipes (and) we'll keep finding other plant benefits. I believe in the colors," McWilliams said.

Powders Lack Benefits

Allicin is found in all the vegetables in the onion and leek family, including chives and scallions, according to The American Dietetic Association. It is not found in garlic salts or garlic powders, Cundiff said, because the freeze-drying process kills the compound. Food/Health Links:

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