I love garlic. I can't think of any savory meal where I don't use it, and I also take garlic supplements. It's something my doctor recommended because she believes it helps regulate digestion and ward off colds. Turns out she's right, at least about the preventing colds part.
A study followed two groups — one that took garlic supplements and another that took a placebo — and found that the garlic group came down with fewer colds, and recovered faster too. Researchers aren't exactly clear why it helps, but some suggest that allicin, a main component of the pungent vegetable, blocks enzymes that play a part in causing infections.
It's also not clear if garlic works after the onset of a cold, or if it needs to be taken as a preventative measure. Until more research comes in, I'll keep taking my supplements regularly.