Breast cancer has now overtaken lung cancer as the world’s most commonly diagnosed cancer, and as the leading cause of cancer-related deaths for women in many countries. While genetics can certainly increase risk of the disease, for most women lifestyle factors, such as alcohol or being overweight or obese, are bigger influences on developing breast cancer. Now, two separate studies, both published in 2020, have identified cow’s milk as another possible risk factor for breast cancer.
The first study, which looked at 33,780 Swedish women since 1997, found that about 300 millilitres of cow’s milk per day (the equivalent of a large mug) increased breast cancer risk by about a third compared to women who did not drink milk.
The second study, from the US, looked at 52,795 over a period of nearly eight years and found that women who drank about 300 millilitres of milk per day had a 50% increased risk for breast cancer compared with those who drank very little milk.
Both studies found that the risk was mostly limited to post-menopausal women who developed a type of breast cancer stimulated by oestrogen, called oestrogen-receptor positive breast cancer. There was no increased risk of other types of breast cancer which rely on other growth factors (such as HER2 positive breast cancer)…