According to a report in the August 8 issue of Archives of Internal Medicine, one of the JAMA/Archives journals, soy isoflavone tablets do not seem to have any effect on bone loss or menopausal symptoms in women within the first five years of menopause.

The article’s background information states that the early stages of menopause are often accompanied by rapid bone loss, hot flashes, vaginal dryness and sleep disturbances among other symptoms. Most of these changes can be prevented with estrogen therapy with or without progesterone. Findings from the Women’s Health Initiative however suggest, that the overall risks outweigh the benefits resulting in most menopausal women choosing to forego estrogen therapy in order to find other alternatives. One of the alternatives suggested in providing comparable benefits to estrogen without the risks are soy-derived products.

A randomized controlled trial that took place from July 2004 to March 2009 conducted by Silvina Levis, M.D., of the Miami Veterans Affairs Healthcare System and Miller School of Medicine, University of Miami, and her colleagues determined the effectiveness of soy isoflavone tablets in preventing bone loss and other menopausal symptoms.

To ensure they received an effective dose of soy isoflavone, participants of the trial were administered the equivalent to approximately twice as much as the highest intake through food sources in a typical Asian diet. Eligibility was restricted to women between the age of 45 to 60 years within five years of menopause and with a bone mineral density T score of -2.0 or higher in the lumbar spine or total hip. The bone mineral density T score referring to the bone density compared with what is normally expected in a healthy young adult of the same sex.

Out of 248 eligible women, 126 were randomly given placebo tablets with the 122 remaining random participants receiving 200 mg of soy isoflavone tablets daily. The result of two years of follow-ups revealed no significant differences between the soy isoflavone group and placebo group in terms of change in bone mineral density of the spine. The differences were limited to -2 percent in the soy isoflavone group compared to -2.3 percent in the placebo group in terms of bone mineral density of the spine and respectively -1.2 percent vs. 01.4 percent for the hip and -2.2 percent vs. -2.1 percent in the femoral neck bone mineral density.

The study further revealed that the number of menopausal symptoms between the two groups was comparable at baseline and at the end of the study, with the exception of hot flashes, which occurred in 48.4 percent of women in the soy isoflavone group compared to 31.7 percent of women in the placebo group at the end of the study. In addition, the authors discovered that a larger number of women in the soy group reported constipation compared with those taking placebo (31.2 percent vs. 20.6 percent) although this was not statistically significant.

The authors concluded:

“Because of concerns regarding the risk of estrogens, a need exists for alternative interventions that could provide the beneficial effects of estrogens in bone and menopausal symptoms without the adverse effects on breast and cardiovascular health. However, we found that our population of women in the first five years of menopause, on average, had low rates of bone loss, and that 200 mg of soy isoflavone tablets taken once daily does not prevent bone loss or reduce bone turnover or menopausal symptoms.”

Katherine M. Newton, Ph.D., of the Group Health Research Institute, Group Health Cooperative, Seattle, and Deborah Grady, M.D., M.P.H., of the University of California, San Francisco and San Francisco VA Medical Center writes:

“Every woman who lives long enough will go through the menopause transition; approximately 80 percent will experience hot flashes and night sweats, and approximately 20 percent will experience sufficient discomfort to seek treatment.”

Levis et al publish the results of the National Institutes of Health-funded Soy Phytoestrogens as Replacement Estrogens (SPARE) trial in this issue of the Archives.

The authors state:

“The SPARE study was designed to overcome the limitations of many prior trials of soy products, including poor design, small sample size and short duration,” but highlight to note, “the main shortcoming of the study was that only 248 of an expected 306 participants were enrolled, and higher-than-expected dropout rates led to a final sample size substantially lower than that predicted. However, even with the smaller sample size, given the virtually identical results in the two groups, it is difficult to imagine that the results would have differed substantially with additional participants or better retention.”

In a concluding statement the authors write:

“Overall it does not appear that soy supplementation will play an important role in osteoporosis prevention. To some extent, we are constrained because the mechanism of hot flashes and night sweats remains unknown. Perhaps efforts should be directed away from the hope of a one-size-fits-all therapy for menopausal symptoms toward using existing treatments to target the symptoms that disturb patients most.”

Written by Petra Rattue