Coumestrol

Levels of coumestrol within individual plants of the same species are variable. Studies of coumestrol levels in alfalfa suggest that there may be a positive correlation between coumestrol production and infection of the plant by viruses, bacteria, and fungi. Higher levels of coumestrol are also found in plants which had been damaged by aphids. Further study is required to fully explain the cause of the correlation between damage, infection, and coumestrol levels. According to the United States Department of Agriculture and Iowa State University database on isoflavanes and coumestrol, coumestrol is found in the following food items: Based on extrapolation from studies done on animals, the maximum tolerable daily intake of coumestrol for human beings has been estimated at 22 μg per kg of body mass. This was calculated by extrapolating from the lowest level at which adverse effects were seen in animals. Although due to the variability of the human diet, the exact amount of coumestrol the average person consumes has not been calculated, studies of phytoestrogen intake suggest that most human diets result in a negligible intake of coumestrol relative to the maximum tolerable daily intake. ==Biological effects on mammals==

Because coumestrol is an estrogen mimic, it is an endocrine disruptor with the potential to affect all organ systems that are regulated hormonally via estrogens. Nervous system Coumestrol and other phytoestrogens have been shown to have an effect on sexual behavior in rats by antagonizing the action of estrogen within the brain; male rats that nursed from females with coumestrol in their diets were both less likely to mount a female rat and less likely to ejaculate, despite producing normal levels of testosterone. Exposure produced similar decreases of sexual behavior in female rats, as a result of the disruption of estrogen dependent gene expression in the brain. Effects were seen in three areas of the hypothalamus, the ventromedial nucleus, the paraventricular nucleus, and the medial preoptic area, all of which play a role in sexual behavior and sexual activity. Female rats that were exposed to coumestrol neonatally did not adopt the lordosis position as much as those that were not exposed to coumestrol. Reproductive system Coumestrol has been shown to accelerate the onset of puberty in mice. A high coumestrol diet has also been shown to induce early development of the vulva and udder of female lambs. In addition to these anatomical abnormalities, exposure to coumestrol has also been shown to alter the estrus cycle of a number of animals, including cows and sheep, resulting in lower rates of fertility. Metabolism Studies have shown that coumestrol has beneficial properties on carbohydrate metabolism in ovariectomized rats, decreasing glycogen levels in skeletal muscle. There is also data indicating that coumestrol lowers plasma cholesterol levels in chicks. These results point to a possibility of coumestrol having a positive role to play against human obesity and diabetes in the future. Menopause Coumestrol and other phytoestrogens are sometimes used as a substitute for hormone therapy in the treatment of menopausal symptoms such as hot flashes and night sweats. However, studies have indicated that phytoestrogen-enriched foods and supplements are not necessarily effective against these symptoms. In addition, studies indicate that coumestrol and other phytoestrogens have an antiestrogenic effect in the brain and, as a result, do not produce the mental health benefits which are seen in estrogen replacement therapy. Researchers at Georgetown University Medical Center have investigated this matter and concluded that phytoestrogens may be used as an effective treatment for breast cancer because of their apoptotic properties, but that it is only safe to do so after menopause, when women have a much lower level of estrogen in their bodies, or when used conjunctively with anti-estrogen therapies. ==Current and future research==

Most research on the biological effects of coumestrol has been conducted on animals because of ethical concerns. There is a need for more human studies to better understand potential human health impacts due to exposure. In addition, further research is required to fully understand the biosynthesis pathway of coumestrol, although it is believed to be similar to that of flavones and isoflavones. Further research is required to understand the exact nature of the relationship between the levels of coumestrol in a plant and the plant's response to pathogens. ==References==