Garlic produces a chemical called allicin. This is what seems to make garlic work for certain conditions. Allicin also makes garlic smell. Some products are made "odorless" by aging the garlic, but this process can also make the garlic less effective. It's a good idea to look for supplements that are coated (enteric coating) so they will dissolve in the intestine and not in the stomach.
Garlic is a triple-whammy: it's antibacterial, antiviral and anti-fungal. Garlic is one food that you should be eating every day.
It is important to note that the garlic must be fresh to give you optimal health benefits. The active ingredient is destroyed within one hour of smashing the garlic, so garlic pills are virtually worthless and should not be used. When you use the garlic, compress it with a spoon prior to swallowing it, or put it through your juicer to add to your vegetable juice. Just be careful not to put too much in as it can cause some unpleasant surprises. A single medium size clove or two is usually sufficient.
Researchers have found that allicin, a chemical found in garlic that gives it its flavor, could be used to fight cancer. It appears that the natural chemical reaction that forms allicin, which occurs when the garlic is eaten or smashed, may penetrate and kill tumor cells.