Plant estrogen, also often called phytoestrogen, is a naturally occurring nonsteroidal compound in plants that shares a chemical structure similar to estradiol compounds — estrogen as it occurs in the human body. A nonsteroidal compound does not contain fat-soluble steroid compounds that have physiological effects on the human body. While plant estrogen is not exactly the same as human estrogen, its effects on the human body are similar. Generally, these plant hormones are not of exactly the same chemical makeup as human hormones and may be weaker, thereby having a lesser, though still potentially significant, effect on the body. Plant estrogen is not considered a nutrient, such as vitamins or minerals, and does not have a role in any major biological function in the body.
There are four major groups of phytoestrogen: isoflavones, flavones, coumestans, and lignans. Isoflavones, flavones, and coumestans are all flavonoids. This means that the chemical structure of the plant pigments has antioxidant properties. Foods containing the highest amount of plant estrogen include soybeans, tofu, tempeh, soy drinks, flaxseeds, sesame seeds, and oats.
Discovered in 1926, plant estrogen was at first only observed as a part of plant biology, and was assumed to have little to no effect on human or animal physiology. As research continued, scientists found that high levels of plant estrogen in red clover had mild effects on the fertility and reproductive systems of grazing sheep. Though the amount of estrogen a plant contains is much less than is found in the human body, the sheep were consuming large amounts of red clover daily and thus were affected by the estrogen in the plants.
Subsequent research has been performed on plant estrogen and its possible beneficial or detrimental effects on the body, specifically pertaining to diabetes and breast cancer. After several studies, scientists are still unclear on whether phytoestrogen may cause or prevent breast cancer. It has been shown, though, that is has a positive influence on women who suffer from the effects of menopause, such as hot flashes, breast soreness, and mood. Further research has suggested that the consumption of plant-based estrogen has a beneficial effect on people who are diabetics or are clinically obese. These studies have shown that ingesting these compounds may improve glucose control and insulin resistance, as well as moderating hyperglycemia and reducing a person's body weight.