Clinical Abstracts: Soy Intake and Hot Flashes
With Comments by Adriane Fugh-Berman, MD
Source: Nagata C, et al. Soy product intake and hot flashes in Japanese women: Results from a community-based prospective survey. Am J Epidemiol 2001;153:790-793.
Design/Setting/Subjects: A questionnaire survey of a randomly selected subset of 1,500 women (1,196 responded), who were participating in the Takayama study, an ongoing prospective observational study of 31,000 residents ages 35 and older (92% of that population) in Takayama, Gifu, Japan. The study assessed diet, exercise, smoking, drinking, and medical and reproductive histories. All participants in the current study were premenopausal in 1992, at the inception of the study, and were assessed in 1998.
Methods: Detailed dietary histories were taken in 1992, including nine specific soy products; isoflavone intake also was calculated. Women who reported hot flashes prior to study inception were excluded, as were women who reported hot flashes during the first year of the study (to minimize possible influences of symptoms on diet). Analysis was performed on 1,106 women; 101 women experienced moderate-to-severe hot flashes.
Results: There was a significant inverse relationship between intake of soy products (both total intake and isoflavone intake) and the hazard ratio for hot flashes (age, total energy intake, and menopausal status were controlled for). Smoking was significantly associated with an increased risk of hot flashes, and parity was inversely related. Adjustment for these variables (as well as intake of other nutrients and use of hormone replacement therapy) did not significantly affect results. For highest tertiles of soy intake vs. lowest tertiles, hazard ratios were 0.33 (95% confidence interval [CI] 0.16-0.67, P = 0.002) and 0.27 (95% CI 0.13-058, P = 0.008).
Funding: A grant from the Ministry of Education, Science, Sports, and Culture, Japan.
Comments: This survey provides indirect evidence that soy food intake as part of a traditional diet may reduce the incidence of hot flashes. The survey was unusually detailed in assessing soy intake; foods assessed included tofu, deep fried tofu, dried bean curd, soy milk, boiled soybeans, and natto (a fermented soy product), all of which are part of a traditional Japanese diet.
In Asia, consumption of legumes (soybeans, other beans, lentils, and peas) provides 25-45 mg/d of total isoflavones, compared with Western countries, where average consumption is less than 5 mg/d. In Japan, where soy consumption is very high, as much as 200 mg/d of isoflavones are consumed.1 Phytoestrogen supplementation, most frequently using soy protein, has been tested for treatment of hot flashes, with mixed results (see Alternative Therapies in Women’s Health, Premiere Issue 1998). Soy product intake may be more effective for the prevention rather than the treatment of hot flashes; it also is possible that traditional foods are more effective than soy powder (fermentation, for example, increases bioavailability of soy). It was surprising that the researchers apparently did not re-assess dietary intake at the time of the substudy; what if diets changed in the six years since diet was assessed?
Reference
1. Knight DC, Eden JA. A review of the clinical effect of phytoestrogens. Obstet Gynecol 1996;87:897-904.
Fugh-Berman A. Soy intake and hot flashes. Altern Ther Women's Health 2002;4:31-32.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content