Short-term effects of high soy supplementation on sex hormones, bone markers, and lipid parameters in young female adults

Abstract

Background High intake of soy products has been suggested to prevent breast cancer, osteoporosis, and cardiovascular diseases. Aim of the study To investigate the effects of isoflavone-containing soy on circulating sex hormones, biomarkers of bone turnover, and lipoprotein profiles. Methods Fourteen young women received in a randomized crossover design 5 soy cookies (52 mg isoflavones) or 5 soy-free cookies (no isoflavones) per day for one menstrual cycle starting one week before menstruation. Serum and urine analyses were performed on day 3 after onset of menstruation (t(1)), 3 days before ovulation (t(2)), 3 days after ovulation (t(3)), during the midluteal phase (t(4)), and again 3 days after onset of the next menstruation (t(5)). Results With the exception of higher progesterone levels at t(2), soy supplementation did not affect the physiologic fluctuations in circulating sex hormones. The ratio of C-telopeptide (a bone resorption marker) to osteocalcin (a bone formation marker) was slightly higher at t(4) during the soy period compared to t(4) during the control period (P Conclusions High short-term isoflavone-containing soy intake slightly affects physiologic fluctuations in bone turnover, but has no significant effects on most circulating sex hormones and on lipoprotein parameters in young healthy women.