Urine phyto-oestrogen metabolites are not significantly associated with risk of type 2 diabetes: the Singapore Chinese health study

We evaluated the relationship between urine concentrations of phyto-oestrogens (isoflavones and lignans) and risk of incident type 2 diabetes in middle-aged and elderly Chinese residing in Singapore. Urine metabolites of isoflavones and lignans were assayed by HPLC among 564 diabetes cases and 564 matched controls in a case-control study nested within the Singapore Chinese Health Study cohort. Participants were free of diagnosed diabetes, CVD and cancer at morning urine collections during 1999-2004. Cases were participants who reported to have physician-diagnosed diabetes at follow-up visits during 2006-2010, whereas controls were randomly selected among those who remained free of diabetes and were matched to the index cases by age, sex, dialect group and date of urine collection. Conditional logistic regression models were used to calculate OR and 95% CI with adjustment for potential confounders. The mean age of the participants at the time of urine collection was 59.8 years, and the average interval between urine collection and diabetes diagnosis was 4.0 years. The multivariate-adjusted OR for diabetes were 1.00 (reference), 0.76 (95% CI 0.52, 1.11), 0.78 (95% CI 0.53, 1.14) and 0.79 (95% CI 0.54, 1.15) across quartiles of urine isoflavones (P-for trend = 0.54), and were 1.00 (reference), 0.87 (95% CI 0.60, 1.27), 1.10 (95% CI 0.77, 1.56) and 0.93 (95% CI 0.63, 1.37) for lignans (P-for trend = 0.93). The results were similar in men and women, as well as for individual metabolites of isoflavones (genistein, daidzein, glycitin and equol) or lignans (enterodiol and enterolactone). The present study did not find a significant association between urine phyto-oestrogen metabolites and risk of type 2 diabetes in Chinese adults.