90% of American women drink the caffeine equivalent of one to two cups of coffee daily. While consumers are acutely aware of caffeine’s impact on energy levels, probably none are aware of the stimulant’s impact on estrogen levels. Indeed, research is just uncovering the complex, yet significant, relationship between caffeinated beverages and hormonal balance.

An intriguing study just out in the American Journal of Clinical Nutrition looked at data from 259 women, average age of 27, comparing blood estrogen levels with caffeine habits. They found that caffeine intake greater than 200 mg/day (approximately 2 cups of coffee) lowered estrogen concentrations among Caucasians by 13% and increased them among Asian women by 59%. The caffeine source was significant — when it came from soda or tea, caffeine increased estrogen concentrations among all races. For older women and African Americans, caffeine intake did not affect hormone levels in a statistically significant way.
Why the differences? Genetic factors influence how estrogen is metabolized. Antioxidants and other compounds may also play a role. Indeed, such compounds are credited for the potentially healthful effects (e.g., lower Parkinson’s risk) observed for caffeine sources such as coffee, cocoa and tea. Further research is merited to explore how caffeine impacts gender-related health outcomes. One alarming study linked higher caffeine intake with a doubled risk of miscarriage. Paradoxically, men are more sensitive to caffeine stimulation than are women. Regardless of gender, children are getting too much caffeine — possibly contributing to sleep and attention problems.
Published March 5, 2012