Researchers at the National Institute of Health, along with other institutions, have released a study online in the American Journal of Clinical Nutrition, stating that Asian women have higher estrogen levels when drinking 200 milligrams or more of caffeine a day. This is about 2 cups of coffee. On the other hand, white women who drank the same amount tended to have lower estrogen levels than those who did not drink this amount of caffeine. The study goes on to say that African American women who drank equally as much as both the Asian women and the white women also had higher levels of estrogen, but the statistics could not confirm whether this was enough to go by.

Their research came from analyzing women who were drinking either caffeinated soda, coffee, green tea or black tea. Coffee seemed to make the most difference in the estrogen levels of all of the women. Asian women had higher levels of estrogen, white women had lower, and African American women’s levels could not be determined. Soda and green tea, however, were shown to produce high estrogen women in Asians, whites, and African Americans.

None of the estrogen levels of the women who were observed changed any of their menstruation patterns, as the researches may have thought. Enrique Schisterman, Ph.D, of the Division of Epidemiology, Statistics and Prevention Research at the Eunice Kennedy Shriver National Institue of Child Health and Human Development (NICHD), NIH Institute said:

The results indicate that caffeine consumption among women of child-bearing age influences estrogen levels. Short term, these variations in estrogen levels among different groups do not appear to have any pronounced effects. We know that variations in estrogen levels are associated with such disorders as endometriosis, osteoporosis, and endometrial, breast, and ovarian cancers. 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.

The authors revealed that 89% of adult females between 18 and 34 years of age drink, on average, 1.5 cups of coffee each day.

The researchers gathered data on over 250 women aged 18 to 44 years from 2005 through 2007. They drank an average of 90 milligrams of caffeine per day – a little more than the equivalent of a cup of coffee’s worth.

The participants came into the clinic from once to three times a week during two of their menstrual cycles. The researchers gathered data on what they had eaten during the previous 24 hours, as well as details on their sleeping hours, smoking, exercise and other lifestyle patterns. Their estrogen levels were also measured.

In an Abstract in the journal, the authors concluded: