Raw crushed garlic supports healthy a immune response in your body because the crushing/mincing (exposure of the garlic to air) produces allicin and diallyl sulfides which go on to support your immune system. The raw factor comes in to play because the act of cooking the garlic wipes out the allicin sulfides which are the key driver of the positive immuno benefits.
Today I ran into a familiar train of thought in the medicinal uses of garlic. Garlic does not only support immuno response but it also fights cancer (which you could argue is something that an immune response system would do anyway). The American Institute for Cancer Research has said that the same allicin sulfides (which appear after garlic is exposed to air - i.e. crushed) in garlic fight cancer but the sulfides are not fully formed until the garlic has been exposed to air for at least ten minutes. Best Life also reported on this finding and they put it like this:
If you eat of cook garlic too soon, the enzyme alliinase will not have time to create the anticancer compounds known as allyl sulfer compounds, decreasing the herb’s cancer-fighting abilities by more than 90 percent.
That is amazing! So to recap; if you are eating garlic for the medicinal value and for its cancer fighting properties you should do two things: crush it and let it sit for at least ten minutes before eating it. And secondly, you should eat it raw or close to it. If you cook it you will cook off the compounds that fight disease and if you eat it too fast you will eat it before the compounds that fight disease ever fully form.
By the way olive oil prevents cancer too; pair these ideas for an even more significant does of cancer risk reduction. :) Food science is so interesting!
...and for more information on disease prevention click through and browse around the archives.
The American Institute for Cancer Research
Best Life, Oct. 2007