Biomonitoring the intake of garlic via urinary excretion of allyl mercapturic acid

Allium vegetables (onions, leeks, chives) and in particular garlic have bee n claimed to have health-promoting potential. This study was conducted to g et insight into the perspectives for monitoring the intake of garlic by a b iomarker approach. Chemically, the biomarker results from exposure to gamma -glutamyl-S-allyl-L-cysteine, which is first hydrolysed by gamma -glutamin e-transpeptidase resulting in the formation of S-allyl-L-eysteine. The latt er compound is subsequently N-acetylated by N-acetyltransferase into S-ally l-mercapturic acid (ALMA) and excreted into urine. The mercapturic acid was measured in urine using gaschromatography with mass spectrometry. Thus the intake of garlic was determined to check the compliance of garlic intake i n a placebo-controlled intervention study. Results indicate that S-allyl-me rcapturic acid could be detected in 15 out of 16 urine samples of garlic su pplement takers, indicating good compliance. In addition, the intake of gar lic was also monitored in a cross-section study of vegans versus controls i n Finland, in which no differences in garlic consumption nor in ALMA output were recorded between vegans and controls. These data indicate good possib ilities for further studies in the field of biomarkers to investigate the p utative chemopreventive effects of garlic and garlic-containing products.