Short-term effects of high soy supplementation on sex hormones, bone markers, and lipid parameters in young female adults.
BACKGROUND
High intake of soy products has been suggested to prevent breast cancer, osteoporosis, and cardiovascular diseases.


OBJECTIVE
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 < 0.05), indicating an uncoupling of bone resorption and formation processes. Serum levels of total cholesterol, LDL cholesterol, and HDL cholesterol were not influenced by soy intake.


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.
Zittermann
Armin
A
Department of Nutrition Science, University of Bonn, Endenicher Allee 11-13, 53115 Bonn, Germany. a.zittermann@uni-bonn.de
Geppert
Julia
J
Baier
Sonja
S
Zehn
Nicole
N
Gouni-Berthold
Ioanna
I
Berthold
Heiner K
HK
Reinsberg
J
J
Stehle
Peter
P
D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001862:Bone Resorption / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D018592:Cross-Over Studies; D019587:Dietary Supplements; D005260:Female; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D006801:Humans; D008055:Lipids / Q000097:blood*; D012016:Reference Values; D030262:Soybean Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D018709:Statistics, Nonparametric; D013997:Time Factors; D044465:White People
D015415:Biomarkers; D012739:Gonadal Steroid Hormones; D008055:Lipids; D030262:Soybean Proteins; D002118:Calcium