Binding of steroid hormones in vitro by water-insoluble dietary fiber

Abstract

Previous work conducted in our laboratory has shown that steroid hormones bind to natural (e.g., brans, oat hulls) and purified (e.g., cellulose, lignin) fiber components. To explore this relationship further, we assessed the in vitro binding of estrone, estradiol-17β, and testosterone to a water-insoluble fiber fraction obtained from composite food samples of 18 Seventh-day Adventist (SDA) novegetarian (NV), 20 SDA lacto-ovovegetarian (LOV), and 15 SDA vegan (V) men. Three-day dietary food records and 72-hr food composites were obtained contemporaneously from each subject. The LOV and V subjects consumed significantly more crude, dietary and water-insoluble fiber than the NV subjects. Waterinsoluble fiber bound an average of 73% of all estrogens tested, and 56% of the testosterone. Binding levels of testosterone were significantly higher in the Vs than in the LOVs and omnivores. Additionally, there was a significant correlation, when all groups were combined, between water-insoluble fiber intakes and binding of estrone and testosterone. These results suggest that diet may modify hormonal status, possibly through binding of steroid hormones by dietary fiber, leading to altered enterohepatic circulation of these hormones.