COMMENTARY

'Alternative' Cures for Hot Flashes: Worthwhile, or a Waste?

Crystal M. Glassy, DO, MPH; Charles P. Vega, MD

Disclosures

March 27, 2014

In This Article

Alternative Therapies for Menopausal Symptoms

A critical review of surveys on alternative therapy among 32,465 women found that the most popular modality was herbal medicine, followed by phytoestrogens, evening primrose oil, relaxation, and yoga.[4] Common alternative therapies that will be explored in this review are phytoestrogens, evening primrose oil, mind/body therapy, exercise, acupuncture, and black cohosh.

Phytoestrogens

Phytoestrogens are plant-derived compounds that are structurally similar to estradiol and act as selective estrogen receptor modulators. Several phytoestrogens have been studied in menopausal women, including soy isoflavones, red clover, and flax.

Soy isoflavones. Daidzein and genistein are soy isoflavones that are largely present in food as inactive glucose conjugates. Their bioavailability is heavily dependent on the bacterial enzymes within the gut that are responsible for cleavage of the glucose necessary for absorption.

Of note, one third of humans have distinctive gut flora that transform daidzein into equol, which is 10- to 100-fold more estrogenic than daidzein or genistein alone.[5] Therefore, an individual's bowel flora is an important factor in the heterogeneity that exists in response to soy. Women with higher levels of equol have been found to have improved menopausal symptoms.[6]

Soy absorption is also influenced by antibiotic use, alcohol intake, and bowel disease. Furthermore, soy products differ in the amounts of isoflavones present, which are dependent on formulation and purity.[7] The variables that exist between soy isoflavone content in a product and an individual’s absorption of that product make the study of soy's effects on vasomotor symptoms quite complex.

A 2013 Cochrane review looking at 43 trials of the effect of phytoestrogens (soy, red clover, alfalfa) on vasomotor symptoms found no significant effect overall on vasomotor symptoms, and no evidence of harm with use up to 2 years.[8] However, significant heterogeneity existed among trials, and many could not be compared in meta-analysis. Some evidence was found that extracts with high levels of genistein (> 30 mg/day) reduced the frequency of hot flashes. However, further investigation is necessary.

The National Institutes of Health (NIH) conducted its own evidence-based review, again finding a significant level of heterogeneity among studies in terms of design, duration, and background diet. Guidance for future studies was put out in a supplemental NIH report.[9] It has remained challenging to summarize results on the true effect of soy on vasomotor symptoms.

Other studies have shown greater promise. A 2011 study showed a significant difference in reduction of hot flashes with the use of soy compared with placebo.[10] A study by Bolaños and colleagues[11] showed a significant tendency in favor of soy, but concluded that definitive results were difficult to establish given the significant heterogeneity found. Although discrepancy exists among studies, the North American Menopause Society recommends 50 mg/day of soy isoflavones for vasomotor symptoms. If there is no resolution of symptoms, a trial of an alternate therapy is suggested.[12]

Because soy has biological properties similar to those of selective estrogen receptor modulators, women with a history of estrogen-dependent cancers, such as endometrial and breast tumors, should be cautioned against the use of soy isoflavones. Those being treated with tamoxifen or aromatase inhibitors should also avoid soy, because of potential antagonism.[13]

Flax. Fewer interventions have studied flax, which is also phytoestrogen-rich. A 2013 review looked at flax interventions for climacteric symptoms and bone mineral density in peri- and postmenopausal women.[14] Among the 12 studies reviewed, 5 looked at the effect of flax consumption on vasomotor symptoms and 6 examined the effect of flax consumption on circulating sex hormone levels. There was no significant effect on either symptoms or circulating sex hormones. The investigators concluded that flax was not indicated for vasomotor symptoms.

Currently, there is insufficient evidence to recommend flax for menopausal symptoms, and further studies are warranted.

Red clover. Red clover contains 4 isoflavones: daidzein, genistein, formononetin, and biochanin A. A 2006 review by Booth and colleagues[15] did not suggest improvement of vasomotor symptoms with red clover use. However, studies reviewed overall were found to have major design flaws, including short duration, low doses, and nonuniform inclusion criteria.

A recent and promising randomized controlled trial showed significant improvement in vasomotor symptoms with red clover compared with placebo.[16] This crossover study with a 90-day washout period included 109 postmenopausal women assigned to receive 80 mg red clover or placebo. Both groups experienced a significant reduction in hot flash frequency and severity compared with placebo.[16] Of note, among the few studies thus far, red clover does not appear to stimulate endometrial or breast tissue.[15]

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