For women who are looking for a natural remedy to address menopause, phytoestrogens are an important alternative. Phytoestrogens used chronically are thought to reduce the risk of certain cancers (breast cancer, bowel cancer, prostate cancer and cardiovascular disease. Many classes of phytoestrogens have been identified to date, including lignans and isoflavones. The different classes of phytoestrogens are found in smaller or larger amounts in most plants. We can attribute to each individual class the plants in which a particular type of phytoestrogen is found in particularly high amounts. For example, cereals are considered the main source of lignans.

Structure of phytoestrogens

Phytoestrogens are similar in structure to female oestrogens secreted by the ovary. They are attributed with both agonistic and antagonistic effects towards oestrogen. Of all phytohormones, isoflavones have the strongest estrogenic action. Although this action is not as strong as that of 17β-estradiol, among populations whose diets are rich in legumes and vegetables, the amount of isoflavonoids in the body can be thousands of times greater than that of steroidal estrogens. Isoflavonoids then compete with endogenous estrogens for access to cell receptors - if the concentration of endogenous estrogens is high, isoflavonoids may exhibit anti-estrogenic properties. When the concentration of endogenous estrogens is low (e.g. during menopause in women) isoflavones can have an estrogenic effect.

What are the characteristics of isoflavones?

Isoflavones are characterised by tissue selectivity in their agonistic and antagonistic effects. This is because there are two types of estrogen receptors in cells, α-receptors and β-receptors. Α-receptors are the main receptors in breast and uterine tissues, while β-receptors predominate in bones and the cardiovascular system. Estradiol has affinity for both types of receptors, while isoflavones 'prefer' β-type receptors. Phytoestrogens exhibit a wide variety of actions by acting not only through oestrogen receptors , but also through metabolic activity.

Many experiments have been conducted to investigate the effect of isoflavones on the most common symptom occurring during the menopause, i.e. paroxysmal flushing of the face. Numerous results from the phytoestrogen group show positive effects against these symptoms - with an increase in isoflavone intake, the frequency of vasomotor complaints can be reduced.

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A review of clinical and epidemiological data suggests that isoflavones may have anti-cancerogenic effects. Some experiments show that phytoestrogens can reduce the risk of breast cancer and even have a preventive effect. This is mainly the case for women with multiple risk factors such as a sedentary lifestyle, obesity or the use of stimulants. Epidemiological data indicate that in female populations with a high intake of isoflavones, the risk of breast cancer is much lower. Furthermore, it appears that isoflavones may exert an anti-estrogenic effect by competing with oestradiol for binding sites, thereby inhibiting the growth of oestradiol-dependent cells. In addition, they may stimulate SHBG in the liver, thereby reducing the amount of free oestradiol in serum.