For a while my research project was black cohosh. This is an herb used as an alternative to hormone replacement. It has been tested thoroughly for estrogenic activity, and has none (an old report claimed it did, but that turned out to be a contaminant). Whether it is effective depends on the study. It may depend on which brand--I'd be cautious of Remifemin, the most popular brand, which lacked the marker compounds for black cohosh (and thus, possibly didn't actually have any black cohosh at all).

That is the problem with "dietary supplements"--anything labelled as such is not FDA regulated, and quality control is not consistent. It may not be what it says. The GNC brand seems to be pretty consistent.

My thinking is, even if it is only as effective as placebo, that's pretty good. Placebo reduces hot flashes by 50%. When I'm that age, I hope someone will give me a sugar pill but convince me it is a potent drug. Hormone replacement is more effective, it reduces hot flashes by 85%. Black cohosh is probably somewhere in between.

My research has been on whether black cohosh, like hormone replacement, increases the risk of breast cancer. Since it is not estrogenic, it is not likely to have that side effect. It seems to act through neurotransmitter receptors in the brain. It did not increase or decrease mammary tumors in my rats. If it also doesn't interact with tamoxifen, it would be a great alternative because tamoxifen causes hot flashes just like menopause.