Eating a clove or two of fresh garlic a day may indeed keep the doctor away, in part because it has immune-boosting, antibacterial, antiviral, and anti-fungal effects. Many of garlic's therapeutic effects are derived from its sulfur-containing compounds, such as allicin, which are also what give it its characteristic smell. In general, garlic's benefits fall into four main categories:

1. Reducing inflammation (reduces the risk of osteoarthritis and other disease associated with inflammation)
2. Boosting immune function (antibacterial, antifungal, antiviral, and antiparasitic properties)
3. Improving cardiovascular health and circulation (protects against clotting, retards plaque, improves lipids, and reduces blood pressure)
4. Toxic to at least 14 kinds of cancer cells (including brain, lung, breast, gastric, and pancreatic)

In addition, garlic may be effective against drug-resistant bacteria, and research has revealed that as allicin digests in your body, it produces sulfenic acid, a compound that reacts with dangerous free radicals faster than any other known compound.

In order to get the health benefits, the fresh clove must be crushed or chopped in order to stimulate the release of an enzyme called alliinase, which in turn catalyzes the formation of allicin.

Allicin, in turn, rapidly breaks down to form a number of different organosulfur compounds. So to "activate" garlic's medicinal properties, compress a fresh clove with a spoon prior to swallowing it, or put it through your juicer to add to your vegetable juice.

A single medium-size clove or two is usually sufficient and is well-tolerated by most people. The active ingredient, allicin, is destroyed within one hour of smashing the garlic, so garlic pills are virtually worthless. Black garlic, which is basically fermented garlic,  and sprouted garlic may contain even more antioxidants than regular garlic.