Asian women who consumed an average two cups of coffee daily had elevated estrogen levels as compared to those who consumed less.
However, Caucasian women who consumed an equivalent amount of caffeine a day had slightly lower estrogen levels than women who consumed less. Estrogen is the main sex hormone in women, essential for the menstruation and reproduction.
Total caffeine intake was calculated from any of the following sources: coffee, black tea, green tea and caffeinated soda. The changes in estrogen levels among the women who took part in the study did not appear to affect ovulation.
Studies conducted in animals had suggested that caffeine might interfere with ovulation, the American Journal of Clinical Nutrition reports.
"The results indicate that caffeine consumption among women of child-bearing age influences estrogen levels," said Enrique Schisterman from the division of epidemiology, statistics and prevention research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).
Over 250 women from 18 to 44 years old participated in the study between 2005 and 2007, according to an NICHD statement.
"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 tied with such disorders as endometriosis, osteoporosis, and endometrial, breast, and ovarian cancers," said Schisterman.
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