Drinking more than two cups of coffee
daily may boost estrogen levels in women and could worsen
conditions such as endometriosis and breast pain.
According to the researchers, women who
drank the most coffee had higher levels of estradiol, a naturally
occurring form of estrogen, during the early follicular phase,
or days 1 to 5 of the menstrual cycle.
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 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 more than one cup
of coffee a day had significantly higher levels of estrogen
during the early follicular phase of their menstrual cycle.
Caffeine intake from all sources was
linked with higher estrogen levels regardless of age, body
mass index (BMI), caloric intake, smoking, and alcohol and
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.
This study provides a basis for believing
that coffee consumption increases estradiol levels. While
these effects are modest with one or two cups, they are more
evident at higher levels of consumption.
and Sterility October 2001;76:723-729