As phytoestrogens

There is much interest in the possible hormonal effects of phytoestrogens in both men and women. The majority of studies conducted in women have examined the ability of phytoestrogens to alleviate menopausal symptoms. Whilst hormone replacement therapy is recommended for women experiencing menopausal symptoms, there remains some uncertainty as to whether HRT can increase the risk of breast cancer. As a result of these concerns, investigations into natural alternatives such as phytoestrogens have received considerable attention. 

Diet effects on cholesterol absorption and excretion measurements are usually not problematic but should be considered. Standard rodent chows from commercial suppliers work well in most instances. However, lot-to-lot variability in some micronutrients, such as phytoestrogens, may complicate interpretation of results from a serial study that spans several months. Semi-purified diets avoid this possibility. The caveat with semi-purified diets is that most have little or no fiber. Mice eat much less of these diets, have reduced gut motility, and less fecal output. 

Ffuman and animal exposure to phytoestrogens usually occurs by two routes, ingestion of food products containing the agents or as over-the-counter nutritional supplements. Ffowever, a number of cosmetic preparations contain certain of these natural estrogens which may be absorbed through the skin. Medical problems associated with administration of hormone replacement therapy, as described in the report of the Women s Health Initiative, have motivated many women to seek nonmedical means of post-menopausal endocrine replacement, such as phytoestrogen supplements. 

S Nishibe, T Deyama, K Hamasaki, T Kawamura, T Tanaka, E Sakai, S Heinonen, H Adlercreutz. Use of Eorsythia leaves as phytoestrogen source. Abstract books of the 1st intematuional conference on polyphenols and health, Vichy-Erance, 2003, p. 225. 

Lignans are composed of two phenylpropanoid units joined together to form an 18-carbon skeleton, with various functional groups connected. They are always found in woody tissues and resins of plants. Several lignans show clinical activity, such as phytoestrogenic, cathartic, antineoplastic, antiviral, and liver protective activities. 

Isoflavones are flavonoids commonly called as phytoestrogens and one of the most extensively investigated polyphenols. These are present in soybeans, soybean products, and other pulses, widely consumed in Asian and Southeast Asian coim-tries. Isoflavones have attracted attention mainly due to their role in the ameliora-ti(Mi of postmenopausal symptoms such as hot flushes and osteoporosis [52,58,59]. The other beneficial and important biological properties have been established which are related to effects on cardiovascular diseases, cognitive functions, and breast and prostate cancers. These conclusions were based on wide-ranging studies and parameters which showed positive effects, for example, reduction of hot flushes, the excretion of Ixme resorption markers, increase in bone mineral density, the lower LDL and total cholesterol, reduction in colon cancer, and modulation of immune function [60, 61]. Chemical structures of some important molecules of these phytochemical classes are represented in Fig. 82.3. 

Isoflavones have a chemical structure similar to that of mammalian estrogens and are referred as phytoestrogens [36]. Isoflavones are quite weak, possessing 1/1000 to 1/10,000 the estrogenic activity of 17-G-p-estradiol. How-... 

Isoflavones have been found in higher concentrations only in the legume family of plants (Fabaceae) and occur in significant amounts only in soybeans and soya bean products. Isoflavones exhibit oestrogenic activity, but also further toxic effects, and are often classified, together with other active compounds, as phytoestrogens (see Section 10.4). 

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