The relationship between urinary genistein levels and serum alanine aminotransferase levels in adults in the USA: National Health and Nutrition Examination Survey 1999-2010

Background Genistein, a phytoestrogen with similarities to female sex hormones, has been shown to protect against oxidative stress and fibrosis in nonalcoholic fatty liver injury in animal studies. However, few studies have examined genistein's effects on liver function in humans. Participants and methods We analyzed data from the National Health and Nutrition Examination Survey from 1999 to 2010. Individuals younger than 21 years, with viral hepatitis, or with serum alanine aminotransferase (ALT) at the extremes of distribution (5% on each extreme) were excluded. Urinary genistein was normalized by urinary creatinine levels. The relationship between normalized urinary genistein (nUG) and serum ALT was examined using linear regression models with and without adjustment for potential confounders, and the differential effect of sex was examined using an interaction term. Results Of the 9864 participants, 52% were female, 50% were White, 24% were elderly, 36% had hypertension, 12% had diabetes, and 8.1% were heavy alcohol drinkers. Serum ALT was significantly lower in the highest quartile compared with the lowest quartile of nUG (22.3 vs. 23.5 U/l; P<0.001). In adjusted models, individuals in the highest quartile had 0.75 U/l lower ALT levels than those in the lowest quartile (P=0.02). We found a significant difference in ALT levels between the lowest and highest quartiles of nUG in males, but not in females (difference in differences=1.77 U/l, interaction P=0.04). Conclusion We found a statistically significant association between higher nUG and lower serum ALT in males, but not in females. The sex-specific role of genistein in mitigating liver disease merits further study.