Caffeine Alters Estrogen in Women

caffeine alters estrogenA new study sponsored by the National Institutes of Health has found that consuming 200 milligrams of caffeine per day or more significantly alters estrogen levels among premenopausal women.

Surprisingly, the effect of caffeine varies to ethnicity as well as the source of caffeine.

The research followed 259 healthy pre-menopausal women through two menstrual cycles. The researchers analyzed the blood together with 24-hour dietary recall, sleep, exercise and other lifestyle factors. The analysis adjusted the final results to weight and age.

The research found that consuming 200 milligrams of caffeine a day or more increased estrogen levels among Black and Asian women, while it lowered estrogen levels among Caucasian women. The most significant change in estrogen was among the Asian women.

200 milligrams of caffeine is equivalent to approximately two cups of coffee.

In the study, published in the American Journal of Clinical Nutrition, caffeine intake came from coffee, tea and soda. While the overall results were consistent among those who drank coffee, those whose caffeine sources came from tea and caffeinated soda had higher estrogen levels – and this was among all the ethnic groups.

As an overall group, the women consumed an average of 90 milligrams of caffeine per day – equivalent to about one cup of coffee. This was less than the current national average of caffeine intake equivalent of 1-1/2 to two cups of coffee per day among U.S. women between 18 and 34 years old.

While estrogen changes have affected ovulation in animal studies, there was no evidence that the estrogen changes affected ovulation in the study – though the ability to test this was limited.

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The researchers concluded that: “Moderate consumption of caffeine was associated with reduced estradiol concentrations among white women, whereas caffeinated soda and green tea intakes were associated with increased estradiol concentrations among all races.”

The study was led by Karen C. Schliep, Ph. D. of the University of Utah, Salt Lake City. Another of the study’s authors, Enrique Schisterman, Ph.D., is a leading researcher at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Dr. Schisterman commented on the study:

“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 level are associated with such disorders as endometriosis, osteoporosis, and endometrial, breast, and ovarian cancers.”

Compiled and written by Case Adams, Ph.D. See some of author’s books.


Schliep KC, Schisterman EF, Mumford SL, Pollack AZ, Zhang C, Ye A, Stanford JB, Hammoud AO, Porucznik CA, Wactawski-Wende J. Caffeinated beverage intake and reproductive hormones among premenopausal women in the BioCycle Study. Am J Clin Nutr. 2012 Feb;95(2):488-97.

Case Adams is a California Naturopath with a PhD in Natural Health Sciences, and Board Certified Alternative Medicine Practitioner. He has authored 26 books on natural healing strategies. “My journey into writing about alternative medicine began about 9:30 one evening after I finished with a patient at the clinic I practiced at over a decade ago. I had just spent the last two hours explaining how diet, sleep and other lifestyle choices create health problems and how changes in these, along with certain herbal medicines and other natural strategies can radically yet safely turn our health around. As I drove home that night, I realized this knowledge should be available to more people. So I began writing about health with a mission to reach those who desperately need this information. The strategies in my books and articles are backed by scientific evidence along with wisdom handed down through traditional medicines for thousands of years.” Case connects with nature by surfing, hiking, running, biking and according to Dad, being a total beach bum.

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