Soy isoflavones versus placebo in the treatment of climacteric  vasomotor symptoms: systematic review and meta-analysis.
OBJECTIVE
The incidence of vasomotor crises during the climacterium varies in women across different populations, and phytoestrogen consumption seems to play an important role in this problem. The aim of this study was to determine whether intervention with soy (dietary, extract, or concentrate), as compared with placebo, reduces the incidence of hot flashes in climacteric women.


METHODS
Only published, randomized, placebo-controlled clinical trials were selected, with a 12-week duration of intervention, having selected postmenopausal women affected with hot flashes attributed to the climacterium (without cancer background). The intervention to be evaluated was soy, as "soy dietary supplement," "soy extract," or "isoflavone concentrate" (genistein or daidzein). The results were expressed as the number of hot flashes, average score of vasomotor symptoms, or average percent reduction in hot flashes within a time unit (day, week, or month).


RESULTS
Nineteen studies were analyzed. The minimum heterogeneity was observed in the "isoflavone concentrate" group. In the "extract" and "dietary supplement" groups, heterogeneity reached an intermediate level, I(2) = 42% and 59.73%, respectively. The overall result showed a standardized mean difference of -0.39 (95% CI, -0.53 to -0.25) in favor of soy as well as -0.45 (95% CI, -0.64 to -0.25), -0.51 (95% CI, -0.79 to -0.22), and -0.20 (95% CI, -0.46 to -0.06) for the "concentrate," "extract," and "dietary supplement" subgroups, respectively.


CONCLUSIONS
Although the overall combined results and the results by subgroups (according to the type of supplement used) showed a significant tendency in favor of soy, it is still difficult to establish conclusive results given the high heterogeneity found in the studies.
Bolaños
Rafael
R
San Marcos University, Lima, Peru. rbolanosd@correo.unmsm.edu.pe
Del Castillo
Angélica
A
Francia
José
J
D000328:Adult; D016001:Confidence Intervals; D019587:Dietary Supplements; D005260:Female; D019584:Hot Flashes / Q000188:drug therapy*; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D008593:Menopause; D008875:Middle Aged; D016017:Odds Ratio; D008517:Phytotherapy / Q000379:methods*; D010936:Plant Extracts / Q000008:administration & dosage; D016032:Randomized Controlled Trials as Topic; D013025:Glycine max; D016896:Treatment Outcome; D016387:Women's Health
D007529:Isoflavones; D010936:Plant Extracts; C040641:genistin; C013908:daidzin