There has been considerable interest in certain bioactive , non- nutrient plant derived Estrogenic compounds and whether they can serve as alternatives to Hormone Replacement Therapy (HRT) in menopause . These phytochemicals exhibit estrogenic actions in humans either by acting as modulators of estrogen receptors ( SERMs ) or as enzyme modulators (SEEMs) . These compounds are called Phytoestrogens. The blanket term Phytoestrogens refers to various plant constituents , their extracts which are available as pills, as well as to synthetic compounds like Ipriflavone, which is similar in structure to estrogen and Isoflavones.
Phytoestrogens consist of three main groups : Isoflavones , Lignans and Coumestans . Of these , the first two are most abundant in nature. There are more than 1000 known isoflavones of which only a few, like Genistein , Diadzein have good biological activity but it is not as yet known which compound has maximum estrogenic activity .
It is interesting to note that Indian diets are rich in Phytoestrogens which are present in whole grains , legumes – peas, beans, lentils, peanuts, seeds, nuts and other podded plants used as food, fruits, vegetables, spices and herbs.The most widely researched has been soy even though Bengal Gram has three times more phytoestrogens than soybean (152.6 mg / 100 g fresh weight vs. 67.8 ).
The great Indian curry is also a rich amalgam of phytoestrogens which contain dietary herbs like turmeric, cumin, fennel, fenugreek, cardamom, cinnamon, saffron and liquorice. These cannot be dismissed as quackery because they do improve hot flushes . Their beneficial effects on the heart and bones are coincidental and recently discovered. Some of the Indian dietary herbs are licenced for use in Germany but their sale is not permitted as drugs in USA but as health foods. Several Indian medicinal herbs like asoka, yashtimadhu, shankpushpi, shatavari etc.also have beneficial effects on the postmenopausal woman, but since they have not been used in the western countries their mechanism of action is not known.
More than 1000 articles have been published on phytoestrogens in the past 0 years ,especially on soy. Most of the evidence on the benefits of phytoestrogens has , however, come from animal studies. The data from human studies has, at most, been conflicting. Hot flushes do show some improvement but effects on urinary and vaginal symptoms is inconclusive. That cancer is prevented is suggested by the fact that Asians who consume lots of soy have lesser breast cancer ; this is supported by circumstantial evidence , but not conclusively proven. It is possible that phytoestrogens prevent the initiation or the beginning of breast cancer but cannot inhibit already existing cancer cells because consumption of soy in early life can prevent cancer but not consumption in late life. For uterine cancer, the data is neither in favour nor against. The area where maximum benefit has been seen is on the heart . Phytoestrogens lower cholesterol levels and have anti – atherogenic effects on the blood vessels . But these are surrogate markers of heart disease and what happens to the clinical markers of heart disease like heart attack and stroke is not as yet known . The relationship between isofavones and Ipriflavone and bone health can at best be termed ‘ provocative ‘ . Once more information comes in, it is likely that Ipriflavone may well turn out to be a good alternative to HRT in the postmenopause for the bones .
As far as soy is concerned ,the amount of Isoflavones is maximum in the primary product i.e. the soybean , is high in the fermented products – tofu , good in flour , lesser in soymilk , though the deficiency is made up by the larger amount that can be consumed , and is much lesser in soy oils and sauce . This is because of differences in preparation and preservation of different foods . Soybeans from different sources also have different amounts of Isoflavones because of differences in species and soil differences due to geographical and environmental influences . Despite yhis variability , it might be better to consume whole soy as food because of benefits from other phytochemicals and nutrients . When eating soy – fortified or enriched foods , it might be wiser to read the labels to determine the content of Isoflavones . It is pertinent to warn , however , that in India , there is , so far , no regulation to ensure this content . Same is true for several isoflavone pills available in the market . Rigid testing is mandatory for treatments in the postmenopause , be it synthetic estrogens or the so called ‘ designer ‘ estrogens ( SERMs) . Not so for phytoestrogens which are viewed as dietary supplements and are therefore not regulated by drug enforcing agencies . Moreover , Americans see these pills as ‘ natural ‘ treatment for menopause and therefore have tended to overdose with consequent antiestrogenic and harmful effects .
Should phytoestrgens be prescribed as treatment ?
Just because there are some potential benefits of phytoestrogens , their use cannot be extrapolated as therapy or treatment.
Are they really safe ?
Soy has a long history of being safe in Asia but to draw conclusions regarding the safety and benefits of increased intake of phytoestrogens is a little unwise and premature at this time.
Should then one adopt a soy diet ?
It is a simplistic view to take that by adopting a diet of one country one can adopt the disease profile of that country . Meaning thereby that by adopting the soy rich diet of the Japanese one cannot have lesser rates of breast cancer or hip fracture . This is because lower disease rates of one country and race may be due to other dietary influences or genetic factors .
Nevertheless , recognizing the health benefits of a modest intake of phytoestrogens , the US – FDA has recommended that 45-50 mg of Isoflavones be consumed per day . This can be obtained from 25-40 g of soyprotein which is equivalent to one serving of soy . This might be true for Americans but for Indians , the most prudent recommendation to make is to partake of wholesome and nourishing diet consisting of 4 or more smaller meals in a day rather than 3 large meals per day , with 5 – 9 helpings of fruits and vegetables . One should have a diet high in fibre , low in fat and meat . One should eat what is locally available and seasonally relevant . This is likely to increase the overall phytoestrogen intake and is much better than any artificial diet .