Coffee, Tea, Estrogen

Caffeine consumption among women of child bearing age influences estrogen levels

(RxWiki News) Most women need a jolt of caffeine in the morning or afternoon. According to new research, that cuppa joe or can of soda may influence your estrogen levels.

A new National Institutes of Health study looked at more than 250 women who drink caffeine – either coffee, tea or caffeinated soda - and found that caffeine affects their estrogen levels.

Caffeine had the most significant effect on Asian women: Consuming 200 milligrams or more a day, equivalent to about two cups of coffee, led to elevated estrogen levels, compared to the estrogen levels of women who drank less caffeine.

"Caffeine may change your estrogen level; ask your doctor."

Drinking 200 milligrams of caffeine daily affected other races differently. It had an opposite effect on white women, as they had lower estrogen levels, compared to women who had fewer milligrams of caffeine. Black women who drank 200 milligrams of caffeine had elevated estrogen levels, though not as high as Asian women's levels and not enough to be deemed significant.

The study found that the type of caffeine consumed by woman affected her estrogenic response. Womens’ response to coffee was identical to their response to caffeine in general. However, drinking more than one cup of green tea or caffeinated soda led to higher estrogen levels in all races.

Changes in the women’s estrogen levels don’t appear to have any short-term health effects, says Dr. Enrique Schisterman, of the Division of Epidemiology, Statistic and Prevention Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), where some of the research was conducted.

However, changes in estrogen level are linked to disorders like endometriosis, osteoporosis, and endometrial, breast and ovarian cancers, he says in a press release.

"Because long term caffeine consumption has the potential to influence estrogen levels over a long period of time, it makes sense to take caffeine consumption into account when designing studies to understand these disorders." said Dr. Schisterman.

The women, who were 18 to 44 years old and participated in the study between 2005 and 2007, visited the study clinic one to three times a week at specific times of two menstrual cycles. During their time at the clinic, they answered questions about diet, exercise, sleep, smoking and other lifestyle factors. The doctors took samples of their blood and measured their reproductive hormone levels.

The research team found that most of the women (89%) from 18-34 years of age drank a caffeine amount that’s equal to 1.5 to 2 cups of coffee a day.

The authors note that caffeine did not affect ovulation in the women, despite previous studies on mice that linked caffeine to ovulation interference.

This observational study was published online in the American Journal of Clinical Nutrition.

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Review Date: 
January 27, 2012