How Does Caffeine Affect Estrogen Levels?

Your morning cup of coffee may be a pleasant ritual, but the effects of the caffeine in your coffee may not occur to you. Like all drugs, caffeine has a variety of effects on the human body. Estrogen, the best-known female sex hormone, is affected by caffeine.

Caffeine

Caffeine is found naturally in the leaves, seeds and fruits of more than 60 plants, including tea, coffee and kola plants. It is also produced synthetically. A central nervous stimulant, caffeine is quickly absorbed by the brain and excreted in the urine many hours later. Common nutritional sources of caffeine include coffee, tea, chocolate and most colas, as well as some medications. Too much caffeine can cause symptoms of anxiety, insomnia, nausea and a fast heart rate.

Estrogen

Estrogen is the hormone that guides the formation of the female reproductive system. The secondary sex characteristics that appear during puberty, such as increased breast size and genital hair, result from increased estrogen levels in the female body. During the menstrual cycle, estrogen rises, stimulating the maturation of eggs. If pregnancy does not take place, the estrogen levels then decline rapidly during the luteal phase–the last two weeks of the menstrual cycle. Estrogen declines in menopause, but production never ceases completely.

Caffeine and Estrogen

A study in the October 2001 issue of "Fertility and Sterility" found that more than one cup of coffee a day increased estrogen in women between the ages of 36 and 45 in the first stage of the menstrual cycle. In a study reported in the June 2005 issue of "Cancer," caffeine intake decreased estradiol, one of the forms of estrogen, during the luteal phase of the menstrual cycle. Both caffeinated coffee and caffeinated tea had this effect. The researchers thought caffeine might inhibit aromatase, a key enzyme in the production of estrogen in the body.

Expert Advice

According to Dr. Michael Lam, a specialist in preventive and anti-aging medicine, a higher caffeine intake has a greater effect on estrogen levels. Lam notes that studies on coffee consumption and estrogen have shown that women who drink four to five cups of coffee a day, about 500mg of caffeine, had nearly 70 percent more estrogen during the early part of the menstrual cycle than women who drink less than one cup of coffee a day. Lam recommends that women limit coffee intake to one or two cups a day.

Further Considerations

Research indicates caffeine has different effects on estrogen at different stages of the menstrual cycle. If you have questions or concerns about caffeine and estrogen, consult a health care professional.

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