Postmenopausal osteoporosis is said to be the result of a sharp decrease in estrogen levels and leads to an increased rate of bone remodeling.8,9,10 Observational studies suggest postmenopausal Asian women who consume diets high in isoflavones have a lower rate of fracture than other groups.11,12 A randomized, double blind trial conducted at three university medical centers in Italy studied 389 postmenopausal women with a bone mineral density (BMD) of less than 795 g/cm2 at the femoral neck and no significant comorbid conditions. Patients took either a placebo or 54 mg of genistein daily for 24 months. Results showed BMD had increased in genistein recipients and decreased in placebo recipients at the anteroposterior lumber spine.
On the opposite end of the spectrum, a Cochrane Database System Review concluded there is no evidence of effectiveness in the alleviation of menopausal symptoms with the use of phytoestrogen treatments (including dietary soy, soy extracts, red clover extracts and other types of phytoestrogens).13 A systemic review from the University of Minnesota evaluated research from the Cochrane Library and Medline from 1966 to March 2004 and, based on the available evidence, found phytoestrogens from soy and red clover did not improve hot flushes.14
However, a report published in Menopause said concluding isoflavone supplements do not significantly reduce hot flash symptoms may be incorrect, adding the lack of discrimination between individual isoflavones contained in heterogeneous isoflavone mixtures from differing sources can be misleading when designing studies, interpreting results and conducting reviews.15
It appears the conflicting messages are not affecting the interest in soy products for health. The Packaged Facts report “Soy Foods and Beverages” estimated total retail sales of soy products reached $2.1 billion in 2007, up 7 percent from 2006. The report also noted one out of every five consumers report they believe consuming soy-based foods and beverages provides, heart-health function (16 percent), cholesterol-lowering properties (11 percent) and potential for menopause symptom relief (10 percent).
Isoflavones can come from other plant sources as well. Red clover extract, for example, contains genistein and daidzen, which makes it a popular option for easing menopausal changes. And much like soy, evidence is inconsistent on whether it is effective in helping menopausal hot flashes.16,17,18,19,20 In a 12-week double blind, controlled trial of 30 postmenopausal women, 80 mg/d was found to significantly reduce hot flashes.21 A randomized, double blind study from Guayaquil, Ecuador, supported the notion that 80 mg/d of red clover supplementation in post menopausal women significantly decreased menopausal symptoms (baseline:27.2+/-7.7; after isoflavones: 5.9+/-3.9; after placebo: 20.9=/-5.3, P<0.05).22
One of the largest studies (n=252), however, discredited the potential of red clover and its effects on menopause symptoms.23 Known as the Isoflavone Clover Extract study, researchers revealed the reduction of daily hot flashes from red clover extract (as Promensil® and Rimostil®, from Novogen) at 12 weeks were similar to placebo; they also noted there was a biological effect from Promensil but not a clinically important one on hot flashes.
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