Approximately seventy percent of all women experience hot flashes and/or night sweats (also called vasomotor symptoms) during the menopause transition (Stearns et al. 2002).  Until recently, estrogen therapy was the treatment of choice for most women who sought treatment for hot flashes.  Since the results of the Women’s Health Initiative in 2002 noted risks of prolonged use of hormone therapy in older postmenopausal women (Roussouw et al. 2002), many women pursue other treatments for their hot flashes, including over-the-counter complementary and alternative medicines (CAMs), including soy isoflavones, black cohosh, and omega-3 fatty acids.  However, there is limited evidence to support the use of these treatments for hot flashes to date.

A recent report from the National Center for Complementary and Alternative Medicine (NCCAM) showed that over 40% of adults in the United States reported used at least one CAM treatment in the past 12 months, and women over the age of 40 were the largest group of CAM users (Barnes, 2008).

Soy Isoflavones and Phytoestrogens (e.g. soy beverages, soy supplements, flax seed). The effect of soy isoflavone extracts on hot flashes has been studied extensively, but most studies have found that they are no more effective than placebo.  Recent reviews (Nedrow et al, 2006 and Nelson et al, 2006) of clinical trials using dietary sources of soy isoflavones (e.g., soy beverages, soy powder) and phytoestrogens (e.g., red clover supplements) have concluded that these treatments were not beneficial in 93% of the 30 studies reviewed.  It is important to note that in many of the trials, hot flashes improved in both placebo and treatment groups, indicating high placebo response rates in these studies and making it difficult to distinguish between the beneficial effects of soy, placebo response, and non-specific effects of monitoring and study participation.

Black Cohosh. There have been five trials comparing black cohosh to no treatment or placebo for the treatment of hot flashes (Osmers et al, 2005; Jacobson et al, 2001; Newton et al, 2006; Hernandez and Pluchino, 2003; Wuttke et al, 2003).  The studies used a range of doses from 20mg to 160mg per day.  Four of these studies showed no improvement in the treatment group versus placebo. While one (Osmers et al. 2005) found that the group treated with black cohosh reported a decrease in hot flashes, black cohosh appeared to be most effective in a subset of women, those with recent onset of menopausal symptoms.

Omega-3 Fatty Acids.  Omega-3 fatty acids have recently been examined as a possible treatment for hot flashes and are an appealing treatment option, as their safety and cardiovascular benefits are well-established.

The results from the first double-blind, placebo-controlled randomized clinical trial of ethyl-eicosapentaenoic acid (E-EPA), a type of omega-3 fatty acid are encouraging (Lucas et al., 2009).   The investigators randomized 120 women to be treated with either 500mg of E-EPA three times a day or with placebo over an 8-week period and compared changes in hot flashes using a hot flash diary.  The investigators found that E-EPA was more effective than placebo in reducing hot flashes, with a 55% average reduction in symptoms in the E-EPA group and a 25% average reduction in the placebo group.  Women in the E-EPA group were three times more likely to experience a substantial improvement (>50% reduction in hot flashes) than those in the placebo group.

It is notable that study participants were selected because they experienced psychological distress and not because of hot flashes alone, although all of the women participating reported experiencing hot flashes.  Depressive symptoms also improved with treatment in both groups.  Therefore, it is not yet known whether women with hot flashes who do not have concurrent psychological distress will have a similar response to E-EPA.

In summary, studies of CAM for the treatment of menopause-related hot flashes have demonstrated that treatments such as soy and black cohosh are not likely to be effective in most women, while the study of omega-3 fatty acids is promising yet too preliminary to conclude definitively that omega-3 fatty acids are effective.  More studies are needed to better assess the efficacy of omega-3 fatty acids in this population.   Women and their clinicians should consider these results as well as potential side effects as they evaluate treatment approaches to managing bothersome hot flashes.

Erica Pasciullo, BA
Hadine Joffe, MD, MSc

Click here to read our previous blog post on phytoestrogens

Lucas et al. Effects of ethyl-eicosapentaenoic acid omega-3 fatty acid supplementation on hot flashes and quality of life among middle-aged women: a double-blind, placebo-controlled, randomized clinical trial. Menopause 2009; 16(2): [Epub ahead of print]

Stearns et al. Hot flushes. Lancet 2002; 360:1851-1861.

Nedrow et al. Complementary and alternative therapies for the management of menopause-related symptoms: a systematic evidence reviewArchives of Internal Medicine 2006 Jul 24;166(14):1453-65.

Nelson et al. Nonhormonal Therapies for Menopausal Hot Flashes: Systematic Review and Meta-Analysis. JAMA. 2006;295(17):2057-2071.

Barnes PM, et al. CDC National Health Statistics Report #12. Complementary and Alternative Medicine Use Among Adults and Children: United States, 2007. December 10, 2008.