According to studies published in Menopause, supplements of black cohosh or red clover did not reduce the average number of hot flashes per week more than placebo, with reductions of 34, 57, and 63 percent, respectively.
"The important message is that all women improved, but there was a large placebo effect, and the botanicals did not work significantly better than placebo," said lead author Stacie Geller from the University of Illinois at Chicago.
“We also found that the botanicals were safe - which is important, since many women will still continue to use them,” she added.
Menopausal treatments aim to relieve symptoms such as hot flashes/flushes and vaginal dryness, which can persist for several years after menopause.
Herbal substitutes for pharmaceutical-based Hormone Replacement Therapy (HRT) such as red clover and black cohosh have grown in popularity as women seek natural alternatives. However there have been no great concerns about their quality.
In the first study, the UIC scientists, in collaboration with researchers from Northwestern, looked at the effects of black cohosh and red clover on the occurrence of hot flashes, compared to placebo and HRT.
Eighty-nine women with mild to severe hot flashes took part in the study. The results of the four-arm, randomized, double-blind clinical trial revealed that the greatest reduction in hot flashes occurred for women receiving HRT (94 percent).
While the botanicals did not perform better than placebo, Geller and her colleagues reported no significant safety concerns for the botanicals, compared to placebo.
For the second study, 66 women from the other trial were studied in order to investigate if the botanicals had an effect on cognitive abilities, particularly verbal memory. The study is reportedly the first to evaluate the cognitive effects of black cohosh.
The women underwent cognitive testing before the start of the trial, and at the end of 12 month's of intervention.
While none of the botanicals had either a beneficial or a detrimental effect on memory, the hormone therapy used in the trial, Prempro, had a slight negative impact on memory.
"Together, these two studies demonstrate that compared to botanicals, only hormone therapy had a beneficial effect on vasomotor symptoms, but this benefit was at the cost of a slight decrease in memory," said lead author of the cognition study, Pauline Maki.
The studies were supported by grants from the NIH Office of Dietary Supplements, the NIH National Center for Complementary and Alternative Medicine, UIC, the UIC College of Pharmacy, Naturex, and Pharmavite.