Perhaps the most marketed herbal phytoestrogen is black cohosh, or black snakeroot (Cimicifuga racemosa), a tall woodland perennial with white torch like flowers native to eastern North America. The rhizome contains triterpene glycosides and many other ingredients that appear to have phytoestrogenic effects. Other traditional herbs sometimes promoted as phytoestrogens, such as dong quai (Angelica sinensis), have little medical evidence to support their use.
Mechanism of Action:
Soy iso-flavones appear to act as selective oestrogen receptor modulators in that they can occupy and block the oestrogen receptor. In premenopausal women with normal estrogens levels, soy therefore would have an overall anti-oestrogen (oestrogen blocking) effect, whereas in postmenopausal women lacking oestrogen, a weak estrogenic effect would be observed. Soy may also increase the excretion of bile acids and lower cholesterol. The mechanism of black cohosh’s phytoestrogen effect is unclear, although it may also inhibit oestradiol binding to oestrogen receptors. It does not appear to contain iso-flavones like soy, and there are conflicting findings on its estrogenic activity. Early reports of luteinizing hormone suppression have been contradicted by more recent research showing no change in gonadotropins or oestradiol. There appears to be no stimulatory effect on oestrogen receptor–positive breast cancer cells.
What is black cohosh
Adverse Reactions, Contraindications and Interactions:
While soy is generally considered safe, it may induce nausea, bloating, and allergic reactions (itchy rashes or even asthma if inhaled as dust) in some people. One study suggested that high midlife soy (tofu) consumption may be associated with cognitive decline in later life. However, educational and social differences between the high- and low-tofu groups may also account for some of these findings. Research findings in regard to the safety of soy in breast cancer patients conflict, with an in vitro study suggesting possible stimulation of oestrogen-dependent breast cell cultures.
Black cohosh may cause nausea, vomiting, hypotension, and even miscarriage. It is absolutely contraindicated in pregnancy. Red clover contains coumarone and should therefore be avoided with anticoagulants. Diets high in red clover iso-flavones have reduced livestock fertility and theoretically could do the same in humans. Flaxseed may cause nausea, diarrhoea and flatulence. Cyanogenic nitrates in flax (especially in immature seed pods) have produced toxic reactions.
