Soy Protein Isolate Powder in Treatment of Postmenopausal 'Hot Flushes'
May 1998; Volume 1: 59
Source: Albertazzi P, Pansini F, Bonaccorsi G, et al. The effect of dietary soy supplementation on hot flushes. Obstet Gynecol 1998;91:6-11.
To assess the effect of daily dietary supplementation of soy protein isolate powder on hot flushes in postmenopausal women, Albertazzi and colleagues carried out a double-blind, parallel, multicenter, randomized placebo-controlled trial of 104 postmenopausal women over 12 weeks. Fifty-one patients (ages 48-61 years) took 60 g (76 mg isoflavones) of isolated powdered soy protein daily, and 53 patients (ages 45-62 years) took 60 g (no isoflavones) of powdered placebo (casein) daily.
Soy was superior to placebo (P < 0.01) in reducing the mean number of hot flushes per 24 hours after four, eight, and 12 weeks. Women taking soy had a 26% reduction in the mean number of hot flushes by week 3 and a 33% reduction by week 4 (P < 0.001). The overall rates of adverse effects were similar. Twenty-five patients dropped out of the study: 11 in soy and 14 in placebo: seven in each group had gastrointestinal side effects.
Soy protein isolate added daily to the diet substantially reduced the frequency of hot flushes in climacteric women.
COMMENT
Whether women can forego or augment hormone replacement therapy (HRT) using a diet rich in phytoestrogens intrigues clinicians and uncomfortable postmenopausal American women.
Few Japanese women who consume a traditional diet rich in soy products complain of hot flushes, and few develop osteoporosis or cancers of the breast, endometrium, or ovary. All of this changes once their diet Westernizes.
In this well-designed but frustrated Italian study, supported in part by Protein Technologies in St. Louis, vitamin E, HRT, and other medications and supplements were not allowed. The women began with a mean of 11 hot flushes per 24 hours in both soy and casein groups. After 12 weeks, the soy group dropped to an average of six hot flushes, and the casein to 7.5 (P < 0.01). An effectiveness drop at eight weeks occurred in summer, "when Italians commonly take their vacations away from home." Soy powder did not appear to alter other menopausal complaints.
The investigators attribute the bulk of the dropout rate to constipation (48%). Some women (24%) also had difficulty with the amount of sticky powder they were asked to dissolve and swallow.
Though the authors lament the absence of a "user-friendly form" of soy to reduce hot flushes, they did not try food. The traditional Asian diet contains approximately 200 mg of phytoestrogens daily, which is commonly consumed as soybeans, miso, and tofu.
Recommendation
Soy is not a replacement for estrogen, but it contains enough isoflavones to reduce, though not eliminate, the hot flushes of menopause. Whether soy has the other beneficial effects of HRT on bone density and coronary artery disease is uncertain. Marinated and quickly stir-fried tofu would be a much better place to start than soy powder.
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