| PDF[?] (Download) | IsoflavonesMenopauseRed Clover (Trifolium pratense) | | Date: October 15, 1999 | HC# 080592-165 |
Re:Red Clover Isoflavones Reduce Cardiovascular Risk to Reduced Arterial Elasticity in Menopausal Women
Nestel PJ, Poneroy S, Kay S, Komesaroff JB, Cameron JD, and West L. Isoflavones from Red Clover Improve Systemic Arterial Compliance But Not Plasma Lipids in Menopausal Women The Journal of Clinical Endocrinology and Metabolism. :.
Age and menopause reduce the elasticity of major arteries (called arterial compliance), that increases the risk of hypertension, cardiovascular disease and possibly hyperlipidemia. Since it is known that estrogen improves arterial compliance and lipoprotein levels, and that Asian women consuming large amounts of phytoestrogens (e.g. isoflavones) have a lower incidence of coronary heart disease, the effects phytoestrogens on these parameters has been investigated. The authors recently showed that soybean isoflavones improved arterial compliance, but not lipoprotein levels, in menopausal and perimenopausal women. This paper reports on the effects of red clover isoflavones on postmenopausal women.
Red clover (Trifolium pratense) contains the isoflavones genistein, daidzein and their methylated precursors biochanin and formononetin. The red clover preparation used in this study was a standardized, proprietary product named Promensil( (Novogen, Australia), which contains 40 mg total isoflavones per tablet comprised of 4.0 mg genistein, 3.5 mg daidzein, 24.5 mg biochanin and 8.0 mg formononetin, all as hydrolyzed aglycones. (The study was supported in part by Novogen Ltd.)
Test subjects were recruited via newspaper advertisement and were clearly postmenopausal based on objective measurements of follicle stimulating hormone (FSH). Subjects were excluded if they were greater than 70 years old; had been taking hormone replacement therapy, evening primrose oil or vitamin E for at least the 6 weeks before the study; were smokers; consumed more than 14 standard alcoholic drinks in a week; had plasma cholesterol between 5-7 mmol/L; had a body mass index greater than 32; or exhibited any signs of cardiovascular disease.
The study design included a three week run-in period during which subjects were given placebo pills and trained with respect to dietary requirements in-cluding avoidance of legumes and soy-based food products, and maintaining a regular food pattern including no more than 30% of energy from fat. Women were then randomly divided into the treatment and placebo groups. The treatment group received 2 placebo tablets/day for five weeks, followed by 1 Promensil (40 mg isoflavones) and 1 placebo tablet for five weeks, followed by 2 Promensil tablets (80 mg isoflavones) for five weeks. The placebo group received placebo throughout. The study was carried out double-blind, with an external monitor supervising the trial.
After each placebo and active period, arterial compliance, arterial pressure, body mass index, blood plasma lipid glucose, cholesterol and triglyceride levels, and urinary output of isoflavones were measured. Arterial compliance was measured by ultrasound as a pressure (carotid artery) and volume (outflow into aorta) relationship. Urine total isoflavone content was estimated using high performance liquid chromatography (HPLC) analysis of 24 hour urine samples. Dietary compliance was monitored every two weeks by a dietitian through interviews and a three day food consumption diary.
A statistical summary of the study follows: of the 26 women enrolled in the study, 13 women completed the entire study, 14 completed the 40 mg isoflavone treatment stage, and 3 took placebo tablets throughout. Results are limited to comparisons of treatment stages for the 13 women completing the entire study using the run-in period as a baseline, and not comparisons to the placebo group. Effects of time and order of the treatment or carry-over were not found to be confounding factors. The mean values for arterial compliance were: run-in, 18.5 ( 6.4; placebo, 19.7 ( 5.7; 40 mg dose, 23.7 ( 5.3; and 80 mg dose, 24.4 ( 4.9. A significant difference between these treatments was found (p < 0.001) using ANOVA with a power of 0.9 to detect a difference of < 5%. Paired t-tests showed the differences for placebo vs. 40 mg treatment to be significant at p = 0.039, and placebo vs. 80 mg treatment to be significant at p = 0.018. Differences between the 40 mg and 80 mg treatments or the run-in and placebo periods were not significant. The mean arterial compliance values for the placebo group, consisting of 3 subjects, were 17, 16 and 16 for the four phases. This demonstrates the consistency of compliance values over time. Differences in arterial pressure, plasma lipoprotein levels, and body mass index were not significant, though there was a downward trend in LDL and an upward trend in HDL cholesterol. Urinary isoflavones increased in a dose-dependent manner with increasing treatment dosage, and reflected at least 25% absorption.
The effects of red clover isoflavones on arterial compliance, arterial pressure, and plasma lipids were similar to those previously reported by the authors for soy isoflavones. These results show that arterial compliance can be changed mechanistically in a short period of time. That other parameters influencing arterial compliance remained unchanged (e.g. arterial pressure) supports the conclusion that improvement in compliance was due to the isoflavone supplements. Though changes in plasma lipids were not statistically significant in the small sample size, a 10% reduction in the LDL/HDL ratio suggests that isoflavones may influence this parameter as well, as has been shown for whole soy protein. - Risa N. Schulman, Ph.D.
Enclosure: Copyright (c)1999, Journal of Clinical Endocrinology and Metabolism,The Endocrine Society. Reprinted with permission. www.endo-society.org
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