Many of us don't function well without a morning cup of coffee to get things started. Some of us require small doses throughout the day in order to function. The caffeine-human relationship has been cultivated for millennia through various relationships with plants from tea to cacao—the fruit chocolate comes from—to our beloved brewed bean and the synthetic versions added to sodas and energy drinks. And while long believed to provide little more than a burst of energy, new research has connected caffeine intake, particularly from the coffee bean, with notable health benefits including an increased immunity to certain types of cancer and a decreased risk of heart disease.

But a recent study published in the American Journal of Clinical Nutrition suggests that caffeine-containing beverages like coffee can actually significantly impact estrogen levels, creating certain concerns particularly for women. The study found that caffeine had different effects on women based on their race: white women experienced lower levels of estrogen while Asian women experienced slightly elevated estrogen levels and black women noted little effects in either direction. Lower levels of estrogen over a long period of time have been connected to an increased risk of osteoporosis and heart disease, while elevated estrogen levels have been connected to breast and uterine cancer.

The study, which was conducted by the National Institutes of Health, analyzed data on more than 250 women who consumed an average of 90 milligrams of caffeine daily—the equivalent of one cup of coffee—and as much as 200 milligrams per day. (Nearly 90 percent of U.S. women between the ages of 18-34 consume the caffeine equivalent of nearly two cups of coffee per day!)

The different impact on estrogen levels by race may have to do with our genetics and the way certain ethnicities metabolize the caffeine found in coffee, said Dr. Enrique Schisterman, an author of the study and senior investigator at the National Institutes of Health. And, interestingly, when women were given caffeine from a non-coffee source such as tea or soda, all women, regardless of race, experienced higher estrogen levels, leading the researchers to look at antioxidants and other compounds in the caffeinated beverages as contributing factors in affecting the hormone levels.

Shifts in estrogen levels can affect ovulation, which can make conception difficult for women attempting to become pregnant. It may also impact the symptoms of premenstrual syndrome, a condition affecting more than 15 million women in the U.S. every year. Altered estrogen levels can also increase the risk for certain types of cancers in post-menopausal women, particularly breast cancer, as well as impact the symptoms of menopause including hot flashes.

But Dr. Schisterman noted that healthy premenopausal women don't need to worry about their caffeine consumption in the short-term; he did suggest more research on the long-term cumulative impact of caffeine consumption was needed to determine the health risks of altered estrogen levels.

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Resources:

http://www.nih.gov/news/health/jan2012/nichd-26.htm

Image: Andrea Willa

Jill Ettinger