Biological effects of isoflavones in young women: importance of the chemical composition of soyabean products.
To examine the hormonal effects of isoflavones, of which soyabean is a rich source, fifteen healthy nonvegetarian premenopausal women were studied over 9 months. They lived in a metabolic suite for between 4 and 6 months where their diet and activity levels were kept constant and their hormonal status was measured over two or three menstrual cycles. During one (control) menstrual cycle a normal but constant diet containing no soyabean products was fed. Then, over a second complete cycle six subjects consumed a similar diet into which 60 g textured vegetable protein (TVP)/d, containing 45 mg conjugated isoflavones, had been incorporated. Three participants had 50 g miso (a fermented soyabean paste), containing 25 mg unconjugated isoflavones, added daily to their diet over a menstrual cycle, and six others consumed 28 g TVP/d, containing 23 mg conjugated isoflavones. Five participants completed a third diet period where they were randomly assigned to consume either the control diet over a cycle, or a similar diet incorporating 60 g of a soyabean product which had had the isoflavones chemically extracted (Arcon F). Follicular phase length was significantly (P < 0.01) increased and peak progesterone concentrations were delayed with 60 g TVP but no effects were observed with Arcon F. The increase in menstrual cycle length did not reach statistical significance in the three three subject who ate 50 g miso/d, but peak progesterone levels were significantly (P < 0.05) delayed. Mid-cycle peaks of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were suppressed with 45 mg conjugated isoflavones as 60 g TVP (P < 0.05 and P < 0.01 respectively). No other changes in sex-steroid hormone levels were observed on any of the other diets. A significant reduction in total cholesterol was found with 45 mg conjugated isoflavones (P < 0.05), but not with 23 mg conjugated isoflavone-free Arcon F. There was no effect of menstrual cycle phase on transit time.
Cassidy
A
A
Dunn Clinical Nutrition Centre, Cambridge.
Bingham
S
S
Setchell
K
K
D000328:Adult; D002784:Cholesterol / Q000097:blood; D004967:Estrogens / Q000008:administration & dosage / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D005498:Follicular Phase; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008598:Menstruation / Q000378:metabolism*; D010937:Plant Growth Regulators; D011374:Progesterone / Q000097:blood; D013025:Glycine max; D013997:Time Factors
D004967:Estrogens; D007529:Isoflavones; D010937:Plant Growth Regulators; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D002784:Cholesterol