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Garlic lowers blood pressure, regulates cholesterol, and stimulates immunity. I’ve talked about the heart disease risk factors, but what about the immunity? Eating garlic appears to offer the best of both worlds, dampening the over-reactive face of the immune system by suppressing inflammation while boosting protective immunity, for example natural killer cell activity, which our body uses to purge cells that have been stricken by viruses or cancer. In World War II garlic was evidently dubbed ‘Russian Penicillin’ because, after running out of antibiotics, that’s what the Soviet government turned to. But does it actually work? You don’t know, until you put it to the test.

For example, how about preventing the common cold, perhaps the world’s most widespread viral infection, with most people suffering approximately two to five colds per year. The first double-blind, placebo-controlled trial to investigate the prevention of viral disease with a garlic supplement. Those randomized to the garlic suffered 60 percent fewer colds, 70 percent fewer days affected, so not only fewer colds but faster recovery, suffering only one and a half days instead of five. So, accelerated relief, reduction in symptom severity, and faster recovery to full fitness. OK, but this study was done nearly 20 years ago. What about all the other randomized controlled trials? There aren’t any—just that one trial to date—but still, the best available balance of evidence then suggests that garlic may indeed prevent occurrences of the common cold.

The common cold is one thing, but what about cancer? Is it a stake through the heart of cancer? Various garlic supplements have been tested on cells in a petri dish or lab animals, but there were no human studies to see if garlic could affect gene expression… until, now.

Eat one big clove’s worth of crushed raw garlic, and within hours you get an alteration of the expression of your genes related to anti-cancer immunity. It’s one thing to see a big boost in the production of cancer-suppressing proteins like oncostatin when you drip garlic directly on cells in a petri dish, but you also see boosted gene expression directly in your blood stream within hours of eating it. Does this then translate into lower cancer risk?

Ten population studies put together, and those reporting higher consumption of garlic only had half the risk of stomach cancer. How do you define high? In each study it was different, from a few times a month to every day, but regardless, those who ate more appeared to have lower cancer rates than those who ate less, suggesting a protective effect. And hey, stomach cancer is a leading cause of cancer-related death around the world while garlic is relatively cheap, widely available, and easy to incorporate into your daily diet in a safe manner, and perhaps the more the better.

The only way to prove garlic can prevent cancer, though, is to put it to the test. Thousands of individuals were randomized to receive seven years of a garlic supplement or placebo. And they did tend to get less cancer and die from less cancer, but the findings were not statistically significant, meaning they could have just happened by chance. Why didn’t we see a more definitive result given that garlic eaters appear to have such lower cancer rates? Well, they didn’t give them garlic; they gave them garlic extract and oil pills, and it’s possible some of the purported active components weren’t preserved in supplement form. One study of garlic supplements found that it might take up to 27 capsules to obtain the same amount of garlic goodness found in just a half of a clove of crushed raw garlic.

What happens if you cook it? If you compare raw chopped garlic to garlic simmered for 15 minutes, boiled for six, or stir-fried for just one minute you can get a three-fold drop in one of the purported active ingredients called allicin when you boil it, even more if you simmer it too long and it all seems to get wiped out by even the minute of stir-frying. What about roasted garlic? Surprisingly, even though roasting is hotter than boiling, it preserved about twice as much. Raw has the most, but it may be easier for some folks to eat two to three cloves of cooked garlic than even a half clove of raw.

What about pickled garlic, or those jars of minced garlic packed in water, or packed in oil, or that fancy fermented black garlic? Though jarred garlic may be more convenient, there is comparatively less garlicky goodness, especially pickled garlic, and the black garlic really falls far behind.

Can you eat too much? The garlic meta-analysis suggests there’s no real safety concerns with side effects or overdosing, though that’s with internal use. You should not stick crushed garlic on your skin. It can cause irritation and if left on long enough, can actually burn you. Wrap your knees with a garlic paste bandage, or stick some on your back overnight, and you can end up like this, or this.

Definitely don’t rub garlic on babies. “But an article online said that topical garlic was good for respiratory disorders, and the girl was congested.”

Look at those blisters! Oh, the poor pumpkin. “Natural” does not necessarily mean “safe.”

Don’t put it on your toes, don’t use it as a face mask, don’t use it to try to get out of military service. But when you instead just eat it like you’re supposed to, there shouldn’t be a problem, though some people do get an upset tummy if they eat a little too much. And you can’t really say no side-effects, given the body odor and garlic breath.

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