Memory Loss & the Brain

Estrogen is a class of hormones present in women's bodies that induces menstruation and female characteristics such as the development of ovaries and breasts. It is produced by the ovaries. During menopause, the ovaries stop functioning and the body stops producing estrogen. This can have long-range effects including osteoporosis and atherosclerosis. It may also cause symptoms such as hot flashes, irritability and depression. Various forms of estrogen can be taken as drugs to offset these symptoms. However, because estrogen alone can cause a high risk of breast cancer, estrogen is usually prescribed in combination with progestin to lower the risk. This combination is called hormone replacement therapy (HRT). HRT may reduce the risk of osteoporosis and heart disease, but may increase the risk of breast cancer and liver disease.

Estrogen has many effects on brain chemistry and behavior. In animals, estrogen can increase the formation of new connections between neurons, which may be one way that the brain stores new information during learning. Female rats given estrogen may learn tasks faster than female rats deprived of estrogen. There is some evidence that women with low levels of estrogen may show impaired thought processes and increased risk of developing Alzheimer's disease. Post-menopausal women taking HRT may show a reduced risk of Alzheimer's disease. However, there is not yet enough evidence from large-scale studies to be certain. Given that estrogen (and HRT) are associated with some serious risks, most doctors do not feel that estrogen should be taken solely for the purpose of protection against Alzheimer's disease. Instead, women should balance the known risks and benefits of estrogen, such as osteoporosis, cancer and heart disease.

To avoid some of the known risks of estrogen, some women take phytoestrogens, or plant-based estrogens. These are found in foods such as whole grains, beans and soy or in dietary supplements marketed as "natural" estrogen. At this point, it is not at all clear what benefits and risks are associated with these phytoestrogens. In fact, it is possible that taking phytoestrogen supplements may carry the same long-term risk of cancer as estrogen alone (see estrogen replacement therapy). Until the safety of these supplements is established, their long-term effects are unknown.

However, there is little risk associated with eating a phytoestrogen-rich diet, since the associated foods (whole grains, beans and soy) have many health benefits -- some totally unrelated to estrogen. Meanwhile, research is underway to document what, if any, risks and benefits are associated with phytoestrogens.