Phytoestrogens are a group of plant-derived molecules so named because they possess an oestrogen-like activity. The major interest in Phytoestrogens in the 1990s arose in part as a result of an observation that Japanese menopausal women suffered significantly fewer hot flushes compared with their western counterparts. They also appeared to have a lower incidence of breast cancer, cardiovascular disease and osteoporosis. The low incidence of these conditions was correlated with the very high levels of Phytoestrogens found in the traditional Japanese diet.
Effects of Phytoestrogens on climacteric symptoms
Although there have been a few studies that they have investigated the effects of soy on the incidence and severity of hot flushes in perimenopausal and postmenopausal women, there have not been any uniformity in the studies and the conclusions are difficult to interpret. Some of the studies have used soy as whole grains on in flour form, while others have utilised isolated soy protein. The results of the studies so far reported are contradictory. Some failed to observe any effects, while others have observed varying degrees of benefit. Soy preparations appear, at best, to nearly halve the incidence of hot flushes, which is somewhat in contrast with the relatively few hot flushes experienced by Japanese women. There are now available on the market, soy preparations in the form of pills or capsules at doses of 50-100mg per day. Again, at best, the preparations reduce the number of hot flushes by half. This is not an obvious improvement on the treatment effects achieved with whole soy and suggest that the effect of these compounds is small. Thus, it would seem that larger studies with large numbers of women experiencing a high incidence of severe hot flushes are needed to resolve the issue of how effective soy is.
Effects of phyto-oestrogens on bone:
The few small studies that have been conducted on the effects of Phytoestrogens on bones have shown a mild but promising effect. In a small study using soy, at a dose of 54mg per day, a highly significant increase in bone mineral density was observed in both the spine and the femoral neck. The increment was similar to that observed with conventional HRT.
Dietary supplements derived from Red Clover contain additional chemicals that are not present in soy and, therefore, may have different biological activity. A few studies performed using Red Clover at doses of 40-160mg per day found no significant effects on the incidence of hot flushes.
Why are the results conflicting? Many factors combine to render it difficult to conduct effective research on complementary medicines. Often financial resources are limited, the same product from different manufacturers may not contain similar ingredients, and the way the ingredients are absorbed and/or metabolised by the body may vary between individuals and this may be important in terms of their effects.
It is also important to realise that a traditional Japanese diet is not only rich in soy, but also has a low ratio of certain fatty acids due to the high consumption of fish. It may be this combination of fish and other types of diet, rather than just Phytoestrogens themselves, that may be important.
Black Cohosh is a native plant from the east of North America that has been used by Native Americans for gynaecological conditions since before the arrival of European settlers. It was called 'Squaw root' because it was used primarily for female disorders. It was the primary ingredient of a tonic for 'female complaints', which sold widely in the USA for more than fifty years in the early twentieth century. In 1989, the German government commissioned an expert panel to address herbal products, and Black Cohosh was approved as a non-prescription medicine for the treatment of climacteric ailments. However, the commission recommended its use for no longer than six months due to an uncertainty about its possible long-term side effects.
The treatment of menopausal signs and symptoms has been the primary therapeutic application of Black Cohosh. It is main ingredient in the often-used over-the-counter menopausal preparation called Remifemine. The mechanism by which Black Cohosh exerts its effects is unclear. It was once believed to have oestrogen-like activity, but the results of studies have been varied. The biologically active component of Black Cohosh is attributed to a number of special chemicals called tryterpine glycosides. Remifemine is standard with respect to these chemicals. In the two studies that have been conducted to study the effects of Black Cohosh on hot flushes, in only one of them was there a statistically significant reduction in symptoms. A note of caution about the use of preparations containing Black Cohosh has to be made as there have been reports of acute hepatitis in relation to its use.