Studies have shown that coffee has a strong effect on increasing estrogen.
Women who drink four to five cups of coffee a day consume more than 500 milligrams of caffeine. This increases estradiol levels by as much as 70% during the follicular phase of a woman's menstrual cycle (days 1 - 5 after the start of menstruation), when high levels of estrogen are particularly dangerous.
The study found that drinking just two cups of coffee from a small coffee cup significantly increased estrogen levels. The more you drink, the higher your estrogen levels. High estrogen levels increase the risk of breast and endometrial cancer, as well as endometriosis and breast pain.
