Distribution of soy intake in a Western population: The Adventist Health Study-2

The benefits of soy intake in reducing risk of cancer have been demonstrated in few Asian populations. Although American consumption of soy is steadily increasing, scientific evidence of its benefits in the US and other Western populations is limited and inconsistent. In addition, few Western populations have high soy intake. We report 1) correlations between soy protein of 11 commercial products usually eaten by Adventists and isoflavone conjugates, and 2) correlates of soy protein intake, assessed by 24 hr dietary recalls from 186 calibration subjects, with urinary isoflavones from 100 of these subjects in AHS‐2. There was between 6.4 and 298.4 mcg of isoflavone/g of product. Correlations between soy protein/100g of product and mcg of daidzein glycosides and aglycones and similar genistein conjugates/g of product were 0.71, 0.35, 0.82, and 0.43. Soy protein intake for 136 white subjects was 4.9 g/d (6.47 g/d among 103 soy consumers); for 49 black subjects, this was 3.51 g/d (4.78 g/d among the 36 soy consumers). Correlations between urinary isoflavones and soy protein intake were 0.743 (daidzein), 0.717 (genistein), and 0.492 (equol). The correlation between daidzein and equol was 0.21. These observed soy intake and isoflavone excretion are comparable to that of Asian populations. We conclude that the soy protein in the products eaten in this sample of subjects is a reasonable indicator for daidzein and genistein glycoside content. Also, estimates of soy protein intake provide a good index of physiologic values in this population.Supported by RO1 CA94594 from the National Cancer Institute.