Black garlic is simply regular garlic that has been fermented for a month. The process that turns garlic cloves dark, changes their consistency into that of jelly, and gives them a sweet taste, which reminds some people of licorice.
Black garlic was introduced in Japan in 2005 and has also been used in Korea and Thailand. In the past few years, it has made a big hit with high-end chefs, who have been using it to flavor fish, chicken, and risotto.
As far as the health claims are concerned, I doubt that there's much evidence to support them, although I did see one report that found black garlic to have stronger antioxidant activity than regular garlic. It looks to me as if the greatest impact of black garlic so far has been among foodies on the lookout for the next novelty item.
If you want to try it, you can order it online and, perhaps, find it in some gourmet food shops. Black garlic is much more expensive than regular garlic - four ounces sell for $7.95 online, and a single head costs about $2 at a New York food specialty shop.
Black garlic may be a bit more glamorous, but remember that regular fresh, raw garlic is a powerful natural medicine. It is an effective antibiotic and antiviral agent that can be used to help treat many kinds of infections. It also contains compounds that appear to fight cancer, and helps lower high blood pressure and high cholesterol.
Andrew Weil, M.D.