A new study published in the International Journal of Epidemiology revealed that intake of dairy milk is linked to a higher risk of breast cancer in women. The study sheds light on how even a single cup of dairy milk can increase the risk of breast cancer among women by 50 percent. 
The study was conducted over a course of 8 years, involving around 53000 women from North America who were initially cancer-free. Their diets were monitored through questionnaires and 24 hours dietary recalls, and the results were based on baseline questionnaires containing information pertaining to the demographics, family history of the condition, alcohol consumption, medicines used, and other such factors.
It was found at the end of the study that around 1060 women developed breast cancer, with an association with dairy milk. There were also important associations with cheese and yogurt. On the other hand, no clear association was found between soy milk and breast cancer.
The scientists conducting the study said that the link between the two might be a result of the sex hormone content in dairy milk, as the cows are lactating and usually also pregnant while producing that milk. Since breast cancer in women is usually a result of hormones such as estrogen and progesterone, dairy milk might insinuate a complication.
The lead researcher in the study, Fraser, said “Dairy milk does have some positive nutritional qualities, but these need to be balanced against other possible, less helpful effects. This work suggests the urgent need for further research.”