Moderate caffeine consumption, found in coffee and other caffeinated beverages, was not “significantly” associated with an overall increased risk of breast cancer, a study in the Archives of Internal Medicine showed. But women with a history of benign cancer disease who consume more than four cups of coffee a day have a “borderline significant risk” for malignant disease.

Researchers from Brigham and Women's Hospital and Harvard Medical School in Boston and colleagues from Tokyo Women’s Medical University in Japan examined the diets of a pool of almost 39,000 women over the age of 45 over a period of ten years. They were asked to provide details about their diet and their coffee habits.

A high-caffeine diet was found to increase the likelihood of growing tumours larger than two centimetres, the researchers reported. The researchers warned that drinking high amounts of coffee or other caffeinated beverages daily may increase the risk for breast cancer in women with bening breast disease and for tumours that are negative for both estrogen receptor (ER) and progesterone receptor (PR). A high caffeine intake raised the risk of developing tumours larger than two centimetres by 79 percent. Drinking more then four cups of coffee daily was associated with a 68 percent increased risk for developing estrogen and/or progesterone receptor-negative breast cancer.

Previous studies have shown that caffeine consumption could protect us against multiple sclerosis, as it blocks the steps in the development of the condition. Moderate coffee consumption was found to reduce the risk of dying from heart disease.