Although soy isoflavones do have estrogenic effects, more trials are needed before they can be recommended as alternatives to standard estrogen replacement during the menopause, say researchers from the United States.
Dr Ann Vincent and Dr Lorraine Fitzpatrick (Mayo Clinic) say that isoflavones derived from soya are structurally similar to 17b-estradiol and selective estrogen receptor modulators and that there is interest in their use as natural alternatives to standard estrogen replacement. Some studies have shown that isoflavones reduced the incidence of hot flushes by 45 per cent. However, this compared with 70 per cent for estrogen replacement therapy and 30 per cent for placebo, they say.
They conclude that long-term, randomised, placebo-controlled trials are required before definite conclusions can be drawn about their use as an alternative to standard estrogen replacement therapy (Mayo Clinic Proceedings 2000;75:1174).