How does soy improve the symptoms of menopause?

Menopause

Dr. Alice Murkies and colleagues ³ from Brighton Medical Clinic in Australia compared the effects of supplementation with soy flour versus wheat flour on the number of hot flushes experienced in a group of post-menopausal women. The number of hot flushes experienced by the women receiving soy flour decreased significantly within 6 weeks. After 12 weeks, the number of hot flushes had significantly decreased by 45% in the women receiving soy flour and by 25% in the women receiving wheat flour.

Dr. Amnon Brzezinski at the Hedassah Medical Centre in Israel ⁴ examined the effects of a standard diet compared to a phytoestrogen-rich diet on menopausal symptoms. One quarter of the total daily calorie intake was replaced with phytoestrogen-rich foods (including tofu, soy drink, tempeh and flaxseed). The women consuming both the standard diet and phytoestrogen-rich diet experienced an improvement in their total scores of menopausal symptoms. However, the women consuming the phytoestrogen-rich diet experienced a 55% reduction in the number of hot flushes compared to the women on the standard diet, where the number of hot flushes were significantly decreased by 35%.

Dr. Paola Albertazzi and colleagues ⁵ at the University of Ferrara in Italy reported that symptomatic women (experiencing over seven hot flushes per day) consuming 40 grams per day of soy protein with its naturally occurring isoflavones had significantly fewer hot flushes than those consuming the non-soy (casein - milk protein) control. The number of hot flushes decreased significantly after two weeks on soy treatment. By 12 weeks of treatment, the number of hot flushes had decreased by 45% with soy treatment compared to the start of the study. The women receiving the non-soy control also experienced a significant 30% decrease in the number of hot flushes after 12 weeks reflecting a strong placebo effect.*

Dr. Scott Washburn and colleagues ⁶ from Wake Forest University, USA, compared the effects on various menopause symptoms, of consuming a carbohydrate control or 20 grams of soy protein with isoflavones in one daily dose or 20 grams of soy protein with isoflavones split into two daily doses. No differences were observed in the number of hot flushes experienced by the women in either group. However, the researchers observed a significant reduction in the severity of hot flushes in women consuming 20 grams of soy protein with isoflavones in two split doses, compared with women receiving the carbohydrate control and the soy protein in one dose.

In the study by Dr. Brzezinski ⁴ discussed above, the women who consumed the phytoestrogen rich diet experienced a more significant reduction in the level of vaginal dryness compared to the women consuming the standard diet.

In an Australian study, Dr. Fabian Dalais and colleagues ⁷ at the Monash Medical Centre in Victoria compared the effects of a soy (as soy grits, providing 52mg of isoflavones per day), linseed or wheat diet on various symptoms of menopause. Women consuming the linseed and wheat, but not the soy experienced significant reductions in the number of hot flushes (41% with linseed and 51% with wheat) compared to baseline. However, only the women consuming soy showed a significant improvement in the measure of vaginal cytology. This suggests that the isoflavones in the soy had effects similar to oestrogen, in stimulating the increase of cells that are capable of producing mucus to lubricate the vagina.

*The results of these and other studies are promising, however, it is clear that a strong 'placebo effect' occurs (which means both the control group and treatment group experience similar effects). Specifically, the studies have shown that subjects receiving the control treatment experienced a 20-35% reduction in hot flushes, compared to subjects receiving soy where a 40-55% reduction in hot flushes has been reported ¹ . More research is clearly needed to determine the role of soy foods and isoflavones in alleviating menopause symptoms.