Dietary fiber and serum 16α-hydroxyestrone, an estrogen metabolite associated with lower systolic blood pressure.

We recently identified an inverse relation between systolic blood pressure (SBP) and serum 16α-hydroxyestrone, a metabolite of 17β-estradiol, in postmenopausal women. Formation of 16α-hydroxyestrone is catalyzed primarily by CYP1A2, a cytochrome P450 enzyme. The objective of this study was to evaluate the relations between known modifiers of CYP1A2 activity and serum 16α-hydroxyestrone in postmenopausal women. We hypothesized that fruits, vegetables, and grains, which contain more soluble fiber (a known inducer of CYP1A2) as a proportion of total fiber, would be more positively associated with serum 16α-hydroxyestrone than legumes, which contain less soluble fiber as a proportion of total fiber. Serum from a population-based sample of 42 postmenopausal women 55 to 69 y of age living in Cook County, Illinois, was assayed for 16α-hydroxyestrone using mass spectrometry. Ordinal logistic regression was used to evaluate the cross-sectional relation between dietary fiber and serum 16α-hydroxyestrone after adjusting for multiple covariates. Compared with dietary fiber from legumes, dietary fiber from fruits and vegetables was associated with a greater log odds (B=0.201, P=0.036) of having higher serum concentrations of 16α-hydroxyestrone. The log odds of having higher serum concentrations of 16α-hydroxyestrone was also lower in African-American women (B=-2.300, P=0.030) compared with white women. These results are consistent with previous studies demonstrating a negative relation between SBP and dietary fruits and vegetables and a positive relation between African-American race and SBP. Further research is needed regarding dietary factors that may influence the serum concentration of 16α-hydroxyestrone.