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Brazilian researchers assigned 38 women to 80 mg of soy isoflavones or placebo for four months.
Soy isoflavones have been well researched for their presumed women's health benefits. Now, a new study in the journal Menopause has linked soy isoflavones to reduced insomnia in postmenopausal women.
Led by Helena Hachul, MD, PhD, of the Federal University of São Paulo, researchers assigned 38 women with insomnia to 80 mg of soy isoflavones or a placebo daily for four months in double-blind, randomized fashion.
Sleep performance was measured in each patient by polysomnography sleep tests.
After four months, the number of patients identified as having moderate to intense insomnia was reduced by 31.5% in the placebo group and 52.6% in the soy isoflavone group. The researchers noted that patients taking soy isoflavones exhibited an average 6% improvement in "sleep efficiency" compared to a 3.6% improvement in patients taking placebo.
While this study serves to benefit the reputation of soy isoflavones for postmenopausal insomnia, the limited sample size of just 38 women should be heeded. Published science suggests that soy isoflavones could have a hand in several other women's health factors, including reduced hot flashes and reduced incidence of breast cancer.