Penn State University researchers conducted a study to determine if garlic possesses anti-cancer properties.  They gave volunteers a nontoxic form of sodium nitrate along with capsules containing 1, 3 or 5 grams fresh garlic, 3 grams aged garlic extract, or 500 milligrams vitamin C for 7 days. The participants’ urine samples were collected and analyzed for several garlic metabolites, including  N-acetyl-S-allylcysteine and N-nitrosoproline, a marker of nitrosation.


Higher levels of N-acetyl-S-allylcysteine correlated with lower amounts of N-nitrosoproline. Three to 5 grams of fresh garlic inhibited nitrosation similarly to aged garlic and vitamin C.


“What we were after was developing a method where we could measure in urine two different compounds, one related to the risk for cancer, and the other which indicates the extent of consumption of garlic,” explained Dr Harrison, who is a professor of human nutrition at Ohio State University. “Our results showed that those were inversely related to one another – meaning that the more we had the marker for garlic consumption, the less there was of the marker for the risk of cancer.”


“The precise mechanism by which garlic and other compounds affect nitrosation is under extensive investigation, but is not clear at this time,” he added. “What this research does suggest, however, is that garlic may play some role in inhibiting formation of these nitrogen-based toxic substances.”


This pilot study was published in the November 15, 2009 issue of the journal Analytical Biochemistry.   It showed an association between a urinary marker of garlic intake and a biomarker for the conversion of nitrites to carcinogenic nitrosamines, a process known as nitrosation. Nitrates found in foods created using high heat including, processed meats and vegetables and are linked to cancer through their conversion to nitrites. In general, approximately twenty percent of consumed nitrates are converted to nitrites.