Dietary glutathione intake and the risk of oral and pharyngeal cancer.

Glutathione, a tripeptide found in a variety of foods, may function as an anticarcinogen by acting as an antioxidant and by binding with cellular mutagens. The association between dietary glutathione intake and risk of oral and pharyngeal cancer was investigated using data from 1,830 white participants (855 cases and 975 controls) in a population-based case-control study conducted in New Jersey; metropolitan Atlanta, Georgia; Los Angeles County, California; and Santa Clara and San Mateo counties, south of San Francisco-Oakland, California, during 1984-1985. The estimated relative risk of cancer among people with the highest quartile of glutathione intake from all sources was 0.5 (95% confidence interval 0.3-0.7). When analyzed by dietary source, however, glutathione intakes derived from all vegetables and from meat were not related to risk of cancer. Only glutathione derived from fruit and from vegetables commonly consumed raw was associated with reduced oral cancer risk. Relative to the lowest level of combined intake of fruit and of fruit-derived glutathione, risk of cancer decreased slightly with increasing intake of fruit glutathione. This analysis was limited, however, by the small numbers of subjects with extreme combinations of intakes. Further studies are needed to distinguish the potential effect of glutathione from that of fruit and raw vegetables per se or from the influence of other constituents in these foods.