``Higher estrogen levels would not be beneficial for women who for example have endometriosis, breast pain and family histories of breast or ovarian cancer, especially arising premenopausally,'' the study's lead author, Dr. Daniel W. Cramer from Brigham and Women's Hospital in Boston, Massachusetts, told Reuters Health.
``It is my personal advice that such women should be discouraged from consuming more than two cups of coffee per day,'' Cramer said.
The study included nearly 500 women aged 36 to 45 who were not pregnant, breast-feeding or taking hormones. All women answered questions about their diets, smoking habits, height and weight. Researchers measured the women's hormone levels during days 1 to 5 of their menstrual cycle.
Women who consumed the most cholesterol and alcohol, and those who consumed more than one cup of coffee a day had significantly higher levels of estrogen during the early follicular phase of their menstrual cycle, according to the report in the October issue of Fertility and Sterility.
In fact, caffeine intake from all sources was linked with higher estrogen levels regardless of age, body mass index (BMI), caloric intake, smoking, and alcohol and cholesterol intake. Women who consumed at least 500 milligrams of caffeine daily, the equivalent of four or five cups of coffee, had nearly 70% more estrogen during the early follicular phase than women consuming no more than 100 mg of caffeine daily, or less than one cup of coffee.
Women aged 40 and older and those who smoked had higher levels of follicle stimulating hormone (FSH), which reflects the number of eggs remaining in a woman's ovaries. FSH tends to increase with age, and high levels of the hormone correspond with fewer eggs. Therefore, the observation that smokers have higher FSH levels suggests that their ovaries are ``older'' than their chronological age, Cramer explained.
``Our study provides a basis for believing that coffee consumption increases estradiol levels,'' Cramer said. ``While these effects are modest with one or two cups, they are more evident at higher levels of consumption.''
SOURCE: Fertility and Sterility 2001;76:723-729.