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The phytoestrogens available from plant sources have been noted to be useful to a certain extent in postmenopausal women, in the reduction of the symptoms associated with menopause.
The term phytoestrogen refers to plant compounds that mimic the actions of the natural hormone estrogen in the human body. Estrogen is essential for a wide range of functions in women, and decreases in the secretion of estrogen during menopause is normally associated with a wide range of disorders. Phytonutrients belongs to the group of flavones or isoflavones.

More than 20 compounds of phytoestrogens are available from over 300 plant sources/products including herbs (such as parsley, garlic, etc.), grains (mainly soy beans, wheat, and rice), fruits (including dates, cherries, and apples) and drinks (such as coffee and wine).

The effect of phytoestrogens on the immune system has been quite controversial. While many researchers suggest that phytoestrogens tend to suppress the immune system, others report that phytoestrogens have a cell based differential effect on the immune system.

The studies opposing the use of soy isoflavones report that about 80% reduction in the function of the thymus gland was noted in animals following the administration of phytoestrogen injections. The effect on the function of the thymus gland resulted in the decreased production of the T-lymphocytes and associated cells.1These effects of phytoestrogen were attributed to its effect on the genes involved in the formation, growth and development of the thymus.

Phytoestrogens Have a Selective Role on the Immune System

On the contrary, it is widely supported that phytoestrogens have a selective role on the immune system wherein, suppressing certain cells while stimulating a few of the immune cells. Animal studies have reported that phytoestrogens stimulate various aspects of the immune system. Studies conducted on mouse models done to evaluate the effects of soy isoflavones on the progression of tumor cells reported that the phytoestrogens had a stimulatory effect on the immune system. A decrease in the progress of the cancer cells were noted in these animals following the administration of isoflavones. The benefit was attributed to the increased activity of the natural killer (NK) cells and cytotoxic T-cells as a response to the phytoestrogens.

soy_products.jpgA recent study performed in Japan supported the above findings.The researchers propose that the effect of phytoestrogen is immune cell dependent. While it suppresses the antigen specific immunity and proliferation of lymphocyte cells, it enhances the effects of the NK cells and T- cells. This effect on the NK cells and T-cells may be beneficial in the prevention of the cancers. Further, the immune suppressant effect may be useful for treatment of autoimmune disorders associated with over-activity of the immune system.

The role of phytoestrogens in the enhancement of immune system needs further research to clearly demarcate the benefits and drawbacks of phytoestrogen.

  • 1. Yellayi S, Naaz A, Szewczykowski MA, Sato T, et al. The phytoestrogen genistein induces thymic and immune changes: a human health concern? Proc Natl Acad Sci U S A. 2002 May 28, 99(11):7616-21
  • 2. Cooke PS, Selvaraj V, Yellayi S. Genistein, estrogen receptors, and the acquired immune response. J Nutr. 2006 Mar, 136(3):704-8
  • 3. Guo TL, McCay JA, Zhang LX, Brown RD, et al. Genistein modulates immune responses and increases host resistance to B16F10 tumor in adult female B6C3F1 mice. J Nutr. 2001 Dec, 131(12):3251-8
  • 4. Sakai T, Kogiso M. Soy isoflavones and immunity. J Med Invest. 2008 Aug, 55(3-4):167-73.