In the study, women answered the number of grapefruit they had eaten every day in the past few years. It was found that half of them ate a grapefruit every day, and 7% of them ate a quarter or more grapefruit every day. Excessive consumption of grapefruit can easily induce breast cancer. Researchers believe that this may be because grapefruit can lead to an increase in estrogen levels in human blood, and hormone levels are related to the risk of breast cancer. How about overeating grapefruit?