JAMA Review: Isoflavones Questionable Treatment for Hot Flashes

PORTLAND, Ore.--Supplementation with isoflavones may not benefit menopausal women suffering from hot flashes, according to a review and meta-analysis comparing the natural therapy alongside several drugs (JAMA, 295, 17:2057-71, 2006).

Researchers from Oregon Health and Science University, Veterans Affairs Medical Center and Women and Providence Health System combed MEDLINE (1966-October 2005), PsycINFO (1974-October 2005), and the Cochrane Controlled Clinical Trials Register Database (1966-October 2005) for relevant, English-language, published, randomized, double blind, placebo-controlled trials providing data on treatment of hot flashes in menopausal women measuring and reporting hot flash frequency or severity outcomes and using one or more oral, nonhormonal therapies. Of 4,249 abstracts found, the researchers selected 43 relevant studies, including 10 trials of antidepressants, 10 trials of clonidine, six trials of other prescribed medications and 17 trials of isoflavone extracts. The number of daily hot flashes decreased compared with placebo in meta-analyses of seven comparisons of selective serotonin reuptake inhibitors (SSRIs) or serotonin norepinephrine reuptake inhibitors (SNRIs), four trials of the antihypertensive agent clonidine, and two trials of gabapentin, a drug commonly prescribed to control epileptic seizures. Frequency of hot flashes was not reduced in meta-analysis of trials of red clover isoflavone extracts and results were mixed for soy isoflavone extracts. The researchers noted the relative efficacy of the treatments cannot be determined, as the trials they reviewed do not compare different therapies head-to-head. The researchers concluded SSRIs or SNRIs, clonidine, and gabapentin trials provide evidence for efficacy; however, effects are less than for estrogen, few trials have been published and most have methodological deficiencies, generalizability is limited, and adverse effects and cost may restrict use for many women, and noted these therapies may be most useful for highly symptomatic women who cannot take estrogen but are not optimal choices for most women.

Since anti-depressants appear to offer some efficacy for hot flashes, black cohosh, which has been shown to act on a serotonin receptor subtype, may produce anti-depressant effects and also provide a safe and efficacious treatment, said Steven Dentali, Ph.D.,vice president for scientific and technical affairs for the American Herbal Products Association (AHPA). "Further, we know that black cohosh does not appear to work through an estrogenic pathway like soy isoflavones do, which should alleviate any concern that black cohosh could produce the same side effects associated with hormone therapy.