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According to urban legend, while garlic oil is harmless when consumed, it’s lethal if it gets into your bloodstream. Supposedly, this is why mafiosi used to coat their bullets in garlic oil—so if the shot was off-center and hit your shoulder or something, it would kill you anyway. I was wondering if you could explain the truth (or lack thereof) or devise some sort of scientific/pseudoscientific experiment so that I and others like me can rest easier at night.—David Bowles, via e-mail

You might think the only parties that need to fear garlic are (a) people stuck in an elevator with somebody who just had a big Italian meal and (b) the undead. Not so. Scientific experiments (and where do you get off insinuating we truck with any other kind?) indisputably prove that garlic kills. Granted, what it mainly kills are lab rats and mice, a fact usually conceded when discussing what a boon to humanity Allium sativum, as the eggheads call it, has otherwise proven to be. Still, I figure the public has a right to know.

First the good news. Not only does garlic have documented antibiotic and anticholesterol properties, but research suggests it may also help prevent cancer and cardiovascular disease. Interestingly in view of your question, as recently as World War II, garlic was used to prevent infection of battle wounds. We now know it’s ineffective for that purpose, but clearly getting it in your bloodstream doesn’t mean certain death.

For all its benefits, garlic has long had the reputation of being one spice-rack staple you don’t want to get on the wrong side of, as its traditional use as a vampire and werewolf repellent suggests. No doubt its mystique stems largely from its notoriously pungent odor and the ease with which it moves through your body to your breath and skin the next day. (What you’re smelling is acetone, the volatile chemical used to remove nail polish, plus other odiferous garlic breakdown products.) Those effects aren’t limited to garlic—other herbs and spices, such as fenugreek, do the same. Garlic oil is especially strong because it’s concentrated, several hundred times as potent as fresh garlic.

A more serious issue is that, though listed as “generally recognized as safe” by federal regulators, in large enough doses, garlic is poisonous. The potentially toxic ingredients are largely the same ones that give garlic its culinary and therapeutic benefits, namely sulfur-containing compounds formed as a natural defense mechanism when the garlic plant is chopped or crushed. The one often touted by garlic enthusiasts is allicin, but be skeptical if anybody tries to sell you some—allicin breaks down quickly, and most commercial garlic preparations don’t contain any. The chemicals of interest are allicin derivatives.

What does garlic poisoning do to you? According to the literature, its effects in humans are diverse enough to include stomach ulcers, bronchial asthma, anemia, vertigo, and suppression of testicular functions. Since garlic also has blood-thinning properties, people with hemophilia shouldn’t take it medicinally.

So, if you’re a Mafia hit man, do you dip your bullets in a little garlic on the theory that if you don’t kill your guy, at least you’ll suppress his testicular functions? I don’t think so—you want a fatal dose. For guidance in this regard, we turn to rodent studies, which indicate that if you feed enough garlic oil to rats, they die of acute pulmonary edema—i.e., fluid in the lungs. The reported 50-percent-lethal doses (i.e., fatal to half the target population) vary quite a bit among the different chemicals in garlic; the lowest one I found, for an allicin metabolite called diallyl disulfide, is 130 milligrams per kilogram of body weight. For a 70-kilogram human (about 154 pounds), we get an LD-50 of 9.1 grams, or roughly a third of an ounce. Fifty-fifty lethality isn’t very impressive, so to be safe we’d better double that to 18 grams. While that may not seem like much, a .38-caliber bullet weighs on the order of 10 grams. Could you pack 18 grams of garlic juice into one somehow? Conceivably, but then what you’ve got isn’t so much a garlic-coated bullet as a ballistic garlic delivery system. I suppose you could use less garlic, but as our earlier discussion suggests, too small a dose could have the undesirable effect of improving the victim’s health. In short, while garlic may inspire fear on a mythic Sicilian-vegetable-of-doom level, as a practical tool of homicide, it stinks.

Incidentally, another danger associated with garlic is potential botulism contamination—in 1989, the FDA banned certain garlic-in-oil mixes for that reason. The problem is that when you chop up fresh produce and cover it in oil, you’re giving anaerobic Clostridium botulinum bacteria a good growing environment. Some claim roasting the garlic first eliminates this danger, but I’ve seen conflicting arguments on that score—better not to risk it.—Cecil Adams

Is there something you need to get straight? Take it up with Cecil on the Straight Dope message board, straightdope.com, or write him at the Washington City Paper, 2390 Champlain St. NW, Washington, DC 20009. Cecil’s most recent compendium of knowledge, Triumph of the Straight Dope, is available at bookstores everywhere.