Effects on menopausal symptoms and acceptability of isoflavone-containing soy powder dietary supplementation

To assess the acceptability of the delivery of an isoflavone supplementation in the form of a powdered drink, and whether the supplementation of dietary isoflavones in this manner decreased the incidence of menopausal flushes. The secondary aims included assessment of other symptoms or parameters of estrogen deficiency and responses to isoflavones.

A randomized, double-blind, placebo-controlled, parallel-group trial comprising 24 postmenopausal women with symptoms of estrogen deficiency was performed over a 12-week period. The women were randomized to receive a dietary beverage containing isoflavones or an isoflavone-free, isocaloric placebo preparation.

Although there was a high compliance rate among individual patients, there was a 25% withdrawal rate from the study in the active group. The incidence of complaints of bad taste tended to be higher in the active group (p = 0.07), and the total number of adverse events was significantly higher in this group (p < 0.001). There was no statistically significant difference in the incidence of flushes between the groups. There was no difference between the groups in Greene Menopause Symptom Scores, vaginal maturation value, levels of follicle stimulating hormone (FSH) or sex hormone-binding globulin (SHBG), or bone turnover markers.

Powdered energy drinks are not commonly consumed in Australia and were poorly tolerated in this study. The high withdrawal rate and reporting of side-effects suggests that other methods of isoflavone delivery may be more appropriate in this culture, in future trials. At the dose used no benefit was seen in relief from menopausal symptoms, although for the sample size, the study could only have been expected to detect major differences between the groups.