Published: Apr 1, 2013
By Kristina Fiore

Full Story:  http://www.medpagetoday.com/Endocrinology/Menopause/38194

Taking soy supplements won’t improve quality of life for postmenopausal women, researchers found.

In a randomized controlled trial, there were no differences in quality of life at 1 or 2 years whether women were taking one of two doses of a soy compound versus a placebo, Paula Amato, MD, of Oregon Health and Science University in Portland, and colleagues reported online inMenopause.

Women in all three of the study arms reported that they were generally “not bothered” by postmenopausal vasomotor and sexual symptoms among others.

“Our results are consistent with most other studies in the literature that show no benefit of soy isoflavone supplementation over placebo,” the authors wrote.

There’s been growing interest in soy and isoflavones for postmenopausal women, particularly as results of the Women’s Health Initiative (WHI) sent women looking for alternatives to hormone therapy, given increased risks of breast cancer and cardiovascular disease.

Isoflavones such as soy have a similar structure to estrogen. The plant-derived compounds have an affinity for estrogen receptors, exhibit estrogen agonist and antagonist activity, and have strong estrogen-independent biological activity.

Indeed, some researchers have noted that Asian women experience hot flashes at much lower rates than North American women, speculating that their high-soy diets may compensate for the postmenopausal lack of estrogen.

The isoflavones found in high amounts in soybeans include genistein, daidzein, and glycitein. But the data on the use of soy supplements among postmenopausal women is both limited and inconsistent.

So to assess the effect of soy isoflavone supplementation on quality of life in postmenopausal women, Amato and colleagues used data from another trial they conducted, called the Osteoporosis Prevention Using Soy (OPUS) Study.

Postmenopausal women were eligible for OPUS if they were between ages 40 and 60, with a serum follicle-stimulating hormone level higher than 30 mIU/mL, and with at least 12 months of amenorrhea. Soy food consumption of less than one serving per week was permitted.

Because the main outcome of OPUS was bone mineral density, only normal-weight postmenopausal women were included, the authors explained.

The 403 women enrolled in the 24-month study were enrolled to placebo or to one of two daily doses of soy supplements: 80 mg or 120 mg.

The aglycone hypocotyl soy isoflavone supplement was predominantly made of a daidzein compound.

Amato and colleagues used the Menopause-Specific Quality-of-Life (MENQOL) questionnaire to assess quality of life at 1 and 2 years. The MENQOL questionnaire includes four domains — vasomotor, psychosocial, physical, and sexual — that retrospectively assess symptoms during the past month. Domain scores range from 1 (not bothered) to 8 (extremely bothered).

Overall, the supplement was well tolerated, compliance was excellent, and retention rates were sufficient to ensure adequate sample size, they reported. The attrition rates at both time points were not significantly different among the treatment groups and the most common reasons for withdrawal were study burden, gastrointestinal upset, and return to hormone therapy.

In the soy groups, serum levels of isoflavones were significantly higher at 1 and 2 years compared with baseline, demonstrating a significant dose-response (P<0.0001).

However, the researchers found no differences between any of the groups at either time point in terms of MENQOL scores at 1 year, and all scores were similar to those seen at baseline.

For instance, in the vasomotor domain, baseline scores were 2.74 for placebo, 3.15 for the 80 mg/d group, and 2.87 for the 120 mg/d group (P=0.18). At 1 year, those scores came in at 2.65, 2.94, and 2.73, respectively (P=0.43).

In the sexual domain, baselines scores were 2.98 for placebo, 2.92 for the 80 mg/d group, and 2.71 for the 120 mg/d group (P=0.53). At 1 year, the scores were 2.80, 2.88, and 2.72 (P=0.83).

Nor were there any differences in endometrial thickness among the 116 women who’d had transvaginal ultrasound.

Amato and colleagues noted two adverse events: one woman in the 120 mg/day group was diagnosed with breast cancer at 14 months, and another in the 80 mg/day group was diagnosed with adenocarcinoma of the endometrium at 21 months. These findings need further investigation, they wrote.

They noted that although the data seem “fairly consistent in indicating that soy isoflavones offer little or no benefit over placebo in quality of life,” their work can’t be directly compared with previous studies because of methodological differences.

The study was also limited because participants had relatively low MENQOL domain scores at baseline and were of normal weight. It’s possible that those with higher scores could have derived more benefit from soy supplementation, as might have those who were overweight or obese.

And participants were, on average, 5 years past menopause, so those in earlier phases may have gained greater benefit.

Finally, the supplement was comprised predominantly of daidzein; supplements with different ratios of isoflavones, particularly those with more genistein, may yield different results, they noted.

Still, they concluded that soy isoflavone supplementation “offers no benefit in terms of quality of life for postmenopausal women.”