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Soy Protein and Hot Flashes

For many post menopausal women the symptoms are familiar: hot flashes, insomnia, nervousness, melancholia, headaches, weakness, vertigo. Although hormone replacement therapy (HRT) has gained wide acceptance as a means of reducing these symptoms of menopause, many women prefer alternatives that are more traditional and less controversial. The possible increase in the incidence of breast cancer in women who have chosen HRT has been a major reason why the popularity of soy products is on the rise in older women.

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Less than 25% of Japanese women complain about hot flashes compared to 85% of North American women. At the same time, Japanese women eating their traditional diet have a lower incidence of breast and other cancers that have been linked to estrogen. The most remarkable difference between the Japanese and North American women is the amount of soy products in their diet. The North American diet contains large amounts of animal and milk proteins. These differ from soy proteins in that animal and milk proteins don't contain isoflavones. Isoflavones are also referred to as phytoestrogens. It is the phytoestrogens that are the active ingredient in soy products. Japanese women consuming a traditional diet consume about 200 mg of phytoestrogens a day. The phytoestrogens found in soy have similar chemical structures to the estrogen hormones that control many metabolic pathways in our bodies. At menopause the levels of estrogens in women's blood drops; adding soy products to the diet may be one way to combat this decline and reduce some of the symptoms of menopause.

A report from Italian researchers in 1998 showed that by adding 60 g of isolated soy protein (which contained 76 mg of isoflavones), the number of hot flash episodes was quickly and dramatically reduced. After three weeks hot flashes were reduced by 26%, 33% by week 4 and 45% after 12 weeks. However, the researchers did have difficulty getting women to adhere to the daily regime and close to 25% of the subjects failed to complete the experiment. Gastrointestinal side effects and constipation were the most common complaints and a large number of women interrupted their treatment during the holiday period. The researchers were able to show that the effectiveness of the soy treatment was directly related to the level of compliance of the subjects.

There has been a great deal of interest in soy products as an alternative treatment for menopausal women. This Italian study is good evidence that soy protein may contain active ingredients that can reduce some of the metabolic changes that occur at this time of life.

Table 1
CHEMICAL STRUCTURES
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  1. Reference
  2. Albertazzi, P., et al., The effect of dietary soy supplementation on hot flushes. Obstet Gynecol, 1998. 91(1): p.91(1):6-11,1

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