Nitrosation is a cellular process in which substances in foods and the water are converted into cancer-causing compounds.  Earl H. Harrison, from Ohio State University (Ohio, USA), and colleagues developed a new urine test that measures for compounds related to cancer risk while detecting the levels of N-nitrosoproline and N-acetyl-S-allylcysteine, compounds abundantly present in garlic.  The team found that the greater the markers of garlic compounds, the less strongly they found the marker for cancer risk.  Writing that “3 to 5 grams of garlic supplements inhibited [Nitrosoproline] NPRO [excretion],” a key marker of nitrosation, the researchers observe that: “It is possible that allyl sulfur compounds found in garlic may inhibit nitrosation in humans.”