S-equol effective in reducing menopausal hot flashes, muscle and joint pain among U.S. women

A dose of 10 milligrams (mg) daily of S-equol delivered via a newly developed fermented soy germ-based nutritional supplement is as effective as a standard dose of soy isoflavones at reducing hot flash frequency significantly and is even more effective for relieving muscle and joint pain, according to a peer-reviewed study in US postmenopausal women published in the June Journal of Women's Health, available now as a Fast Track article online ahead of print.

"This study provides evidence that daily doses of the supplement S-equol, a metabolite of the soy isoflavone daidzein, reduced hot flash frequency and relieved muscle and joint pain in U.S. postmenopausal women. These findings confirm earlier studies in Japanese women documenting S-equol's ability to relieve menopausal symptoms," said Belinda H. Jenks, Ph.D., coauthor of the study and director of Scientific Affairs & Nutrition Education at Pharmavite LLC. Development and ongoing research of a supplement containing S-equol is conducted by the Saga Nutraceuticals Research Institute of Otsuka Pharmaceutical Co., Ltd. Pharmavite LLC, the makers of Nature Made- vitamins and minerals, is a subsidiary of Otsuka, which supported the study.

Daily doses of the supplement containing 10, 20 or 40 mg of S-equol each reduced the frequency of moderate to severe hot flashes similarly to a 50 mg dose of a soy isoflavone supplement in a double-blinded randomized study involving 102 US postmenopausal women aged 45 to 65 who experienced more than 35 hot flashes weekly when they enrolled. The investigators used a standardized soy isoflavone supplement for comparison in the study because of the scientific consensus that extracts or concentrated soy isoflavones support relief of hot flashes in menopausal women, based on placebo-controlled studies.

The investigators observed, after eight weeks of treatment, significant reductions occurred from the study start in the women's average daily hot flashes, the study's primary endpoint. These reductions were comparable for all three S-equol treatment groups, 10, 20 or 40 mg, which ranged from decreases of 3.09 to 3.66 hot flashes daily, to that of the soy isoflavone group, which averaged decreases of 2.92. The average number of daily hot flashes in all of the participants at the study start was 10.0 - 4.03.

Muscle and joint pain improved significantly for both the 10 and 20 mg doses of S-equol compared with the soy isoflavonesnot at all,' 1 was 'a little,' 2 was 'quite a bit' and 3 was 'extremely,' to produce scores.

"These U.S. data expand on the previous studies in Japanese women and further document that a minimum daily 10 mg dose of S-equol would likely help women by both reducing the frequency of their hot flashes as well as decreasing their muscle and joint pain associated with menopause," said Jenks.

Further, for women who had more than eight hot flashes daily at the study start, both 20 and 40 mg S-equol were significantly better than the soy isoflavones in reducing hot flash frequency (p=0.045 and p=0.001, respectively), while the 10 mg S-equol dose had a strong positive trend (p=0.063), according to a sub-group analysis. This finding suggests that the S-equol supplement might be more useful for the women who have a higher frequency of hot flashes, Jenks said.

Also, more women in the 10, 20 and 40 mg S-equol groups achieved a reduction of 50 percent or more in their hot flash frequency by the study end than in the soy isoflavone group: respectively, 25.0, 27.3, 42.9 (P=0.056) and 16.0 percent.

No significant differences occurred between any of the S-equol groups and the soy isoflavone group for two secondary endpoints: the hot flash severity and the psychological (anxiety, depression), somatic (physical), vasomotor GCS subscales. Throughout the eight-week intervention, the women maintained a daily diary to record the frequency and severity of their hot flashes, rating them as mild (sensation of heat without sweating), moderate (sensation of heat with sweating, able to continue activity) or severe (sensation of heat with sweating, causing cessation of activity).

No trends or clinically meaningful changes were identified in the women's laboratory blood or urine tests, hormone levels, electrocardiographs, physical examinations or vital signs. The trial investigators noted treatment-emergent adverse effects in participants of all the treatment groups. Such effects occurring in more than 10 percent of any S-equol group included abdominal distention (eight women) and endometrial hypertrophy (three women), the thickening of the lining of the uterus. The endometrial hypertrophy was identified by transvaginal ultrasounds and was assessed by the Medical Monitor; any changes observed were not considered to be clinically significant.

Of note, Jenks explained, endometrial hypertrophy developed in three women in the 10 mg S-equol group but only one and none in the 20 mg and 40 mg S-equol groups, respectively, which suggest that S-equol does not affect endometrial hypertrophy. Moreover, gastrointestinal disorders in the seven women in both 10 mg and 20 mg S-equol groups as well as the one in the 40 mg S-equol and two in the isoflavone groups, may have resulted from the naturally occurring dietary fiber in the fermented soy germ-based nutritional supplement containing S-equol and from the lactose in the placebo tablets used to match the total number of tablets in each group.

At enrollment, the women had not experienced a menstrual period in the previous 12 months and their levels of follicle stimulating hormone (FSH) were 40 or more milli international units/milliliter, a marker of menopause. The women were in good health. Investigators did not enroll anyone with a history of breast, ovarian or uterine cancer or endometrial hyperplasia, with a body mass index of 33 kg/m2 or more or who had used hormone replacement therapy within 90 days of the study or soy, phytoestrogens or certain other supplements within 30 days of the study, as well as fitting certain other exclusion criteria.

Investigators randomized the 102 women into four groups to consume twice daily either the isoflavone (26 women) or one of the three doses of the S-equol supplement (24 in the 10 mg, 27 in the 20 mg and 25 in the 40 mg groups). The lowest dose of S-equol used, 10 mg, was based on preliminary studies that investigated the relationship between S-equol and menopausal symptoms including hot flashes in Japanese women, while the higher doses were used to reflect the larger body mass in Western women and to establish a dose response. The S-equol supplement tablets each contained 5.0 mg S-equol, 1.0 mg daidzein, 1.1 mg genistein, and 2.5 mg glycitein. The soy isoflavone tablets contained 24 mg daidzein, 22 mg genistein, and 2.0 mg glycitein as aglycone equivalent. The placebo tablets contained lactose.

The women had diets controlled for soy foods, isoflavones and lignans, compounds found in certain plants that are known as phytoestrogens because of their estrogen-like properties. The study included a seven-day period before the treatment weeks to allow for elimination of any women who responded to a placebo. Women also were tested to determine their ability to produce S-equol after eating soy. The study included 72 percent equol nonproducers and 28 percent equol producers, which represents the previously reported US equol producer ratio. The investigators randomized the equol producers equally into each of the study's treatment groups.

No previous studies have reported the effects of either soy isoflavones or S-equol on muscle and joint pain. Recent studies conducted with Japanese postmenopausal women documented that measures of neck or shoulder muscle stiffness improved with daily consumption of 10 mg S-equol supplements, compared to a placebo, as well as reduced the frequency of hot flashes. While muscle stiffness and muscle pain can result from impaired local blood flow and both soy isoflavones and S-equol are thought to affect blood flow, this new study suggests that S-equol may potentially be more effective than isoflavones, Jenks explained.