Red Clover Improves Heart Health After Menopause
Many researchers have proposed a link between the isoflavone-rich
Asian diet and a lowered risk of menopausal problems in Japanese
women, including reduced rates of cardiovascular disease. In one
of the first published studies on a purified red clover extract
(Trifolium pratense L., Fabaceae) scientists found that
the supplement improved arterial compliance (a measure of elasticity
of the large arteries) in postmenopausal women (Nestel et al.,
1999). Declining arterial compliance during and after menopause
is known to increase a woman's chance of developing heart disease
later in life.
Researchers in Australia tested two different dosages of red
clover extract against placebo in this randomized, double-blind,
placebo-controlled study. After an initial three to four week
run-in period and a five-week placebo period for all 17 participants,
the women were divided into two treatment groups for an additional
10 weeks. During the first five weeks of active treatment, women
took either one red clover tablet (40 mg isoflavones) and one
placebo tablet daily, or two placebo tablets daily. During the
final five weeks of the study, the dosage for the red clover group
was increased to two red clover tablets (80 mg isoflavones) daily.
The red clover extract (Promensil®, Novogen Ltd., North Ryde,
Australia) was standardized to contain the following isoflavones:
4 mg genistein, 3.5 mg daidzein, 24.5 mg biochanin, and 8 mg formononetin.
At the beginning of the study, all women were free of obvious
cardiovascular disease. Participants were required to discontinue
the use of any drugs or supplements that might affect cardiovascular
health for at least six weeks prior to treatment, and were instructed
to avoid eating isoflavone-rich legumes such as soy throughout
the study. At the end of each period (run-in, placebo, and two
active periods), researchers measured arterial compliance using
ultrasound, as well as isoflavonoid absorption and serum cholesterol
levels.
The results of the study revealed a statistically significant
increase in arterial compliance in the red clover group, compared
to placebo (a value of 23.7 versus 16 in the placebo group). No
side effects were reported. The effects on heart health were similar
to those of a 1998 placebo-controlled study on hormone replacement
therapy (HRT), which found a 24 percent greater value in arterial
compliance in those taking HRT. The results of red clover treatment
are especially impressive considering the number of serious side
effects associated with HRT, such as an increased risk of depression,
high blood pressure, breast cancer, and other problems. In this
study, there was also a 10 percent downward trend in the ratio
of harmful LDL cholesterol (which decreased) versus healthful
HDL levels (which increased), although the change was not statistically
significantly different from placebo measurements. There appeared
to be little difference between the effects of the two dosage
schedules (40 and 80 mg of isoflavones) tested in this study.
An important drawback to this study was the small sample size
of 17 participants, which included a placebo group of only three
women. Data from the placebo group was not subjected to statistical
analysis because of the small number of subjects. Interestingly,
the placebo group originally included five women until two dropped
out, citing a return of "intolerable menopausal symptoms requiring
hormone replacement treatment." Although this study was not specifically
designed to test red clover's effects on menopausal symptoms such
as hot flashes, it is interesting to note that no one taking red
clover dropped out due to uncomfortable menopause-related complaints.
- Krista Morien
[Nestel PJ, Pomeroy S, Kay S, Komesaroff P, Behrsing J, Cameron JD, West L. Isoflavones from
red clover improve systemic arterial compliance but not plasma lipids
in menopausal women. Journal of Clinical Endocrinology and Metabolism
1999; 84(3): 895-898.] |
