Diet, GSTM1 and GSTT1 and head and neck cancer.

A decreased incidence of squamous cell carcinoma of the head and neck (SCCHN) associated with fruit and vegetable intake may act through chemopreventive compounds, which may be more available to persons homozygous for the deletion genotypes of the glutathione S-transferase (GST). We evaluated interactions between fruits and vegetables and GSTM1 and GSTT1 on incidence of SCCHN using data from a case-control study of 149 cases and 180 age- and gender-matched controls. After adjustment for age, gender, race, tobacco and alcohol use, weekly consumption of four or more servings of raw vegetables was inversely associated with SCCHN [odds ratio (OR) = 0.66, 95% confidence intervals (CI) 0.30-1.3]. Contrary to expectation, relatively high intake of cooked vegetables (14 or more weekly servings) and legumes (two or more weekly servings) were associated with increased incidence (OR = 2.5, 95% CI 1.1-6.0; OR = 2.5, 95% CI 1.2-5.2, respectively). In general, our results did not suggest a clear or consistent pattern of modification by GST genotypes of the association between foods and SCCHN. For example, eating cruciferous vegetables, foods of a priori interest, and having the GSTM1-deletion genotype was not associated with the expected reduction in incidence compared with abstaining from cruciferous vegetable intake and having the GSTM1-present genotype. Among non-consumers of cruciferous vegetables, the GSTM1-deletion genotype was inversely associated with SCCHN (OR = 0.55, 95% CI 0.07-4.2). Raw vegetables were associated with a reduction in incidence only among persons with the GSTM1-deletion genotype (OR = 0.69, 95% CI 0.29-1.6), whereas either factor alone had a null association. Future research of GST-diet interactions and SCCHN would benefit from larger, population-based studies.