Effects of prune consumption on the ratio of 2-hydroxyestrone to 16α-hydroxyestrone

Abstract

Background: A higher urinary ratio of the biologically inactive estrogen metabolite, 2-hydroxyestrone (2OHE1), to the biologically active metabolite, 16α-hydroxyestrone (16αOHE1), may be associated with a lower risk of breast cancer. High fiber intake is also associated with decreased breast cancer risk. Objective: We investigated the effects of prunes, which are naturally rich in both soluble and insoluble fiber, on the concentrations of 2OHE1 and 16αOHE1 and on the ratio of 2OHE1 to 16αOHE1. Design: Nineteen healthy premenopausal women consumed their habitual diets for 3 menstrual cycles and then consumed 100 g prunes/d for the next 3 cycles. Concentrations of urinary 2OHE1 and 16αOHE1 were determined during the follicular and luteal phases. Results: Prune supplementation increased total and soluble fiber intakes by 4 and 2 g/d, respectively (P < 0.001). Mean (± SEM) luteal 2OHE1 excretion decreased from 3.92 ± 0.79 to 2.20 ± 0.40 nmol/mmol creatinine during the third cycle (P = 0.017). Luteal 16αOHE1 excretion decreased from 1.38 ± 0.24 to 0.87 ± 0.10 and 0.87 ± 0.15 nmol/mmol creatinine during the first and third cycles, respectively (P = 0.018 for both values). Follicular 16αOHE1 excretion decreased significantly only during the first cycle (from 0.82 ± 0.12 to 0.45 ± 0.09 nmol/mmol creatinine; P = 0.005). The 2OHE1-16αOHE1 ratio did not change significantly after prune supplementation. Conclusions: Prune supplementation significantly decreased the excretion of 16αOHE1 during the follicular phase of the first menstrual cycle and during the luteal phases of both the first and third menstrual cycles. The 2OHE1-16αOHE1 ratio did not change significantly. The potential significance of the decrease in 16αOHE1 excretion, without a change in the 2OHE1-16αOHE1 ratio, on the prevention of estrogen-dependent cancers remains to be determined.