Red Clover

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 sectors 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.

Japanese Diet
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.