A recent study published in the International Journal of Epidemiology concluded that higher intakes of dairy milk were associated with greater risk of breast cancer. Those with the highest consumption (90th percentile) of dairy milk had a 50% increased risk of developing breast cancer when compared to those consuming the least amount of dairy milk (10 th percentile). To a less extent, there was a 22% increased risk of developing breast cancer when dairy calories were compared between the two groups, demonstrating consumption of other dairy products may too be a risk factor and that the quantity of dairy consumption is also important.
Although the cause of this association was not investigated in this study, it was proposed that the findings could be a result of the sex hormone content of dairy milk. Some breast cancers are hormone sensitive, responding to and growing in the presence of hormones. Intake of dairy and animal proteins also correlate with higher blood levels of a chemical messenger called IGF-1, which can promote certain cancers.
With the results of this study, a sound recommendation for those with risk factors for breast cancer (personal history, family history, radiation exposure, obesity etc.) is to be cautious about dairy milk and use unsweetened non-dairy alternatives such as soy milk, almond milk, coconut milk or cashew milk when available.