Whole milk intake is associated with higher cancer mortality, including lung, ovarian, and prostate cancer, potentially due to biological mechanisms such as increased insulin-like growth factor 1 or galactose metabolism, though these mechanisms remain unproven in humans.

Drinking whole milk increases saturated fats in the blood, which raises bad cholesterol and causes inflammation. It also boosts a growth hormone called IGF-1, which tells cells to multiply faster and stop dying. These two effects together create an environment where abnormal cells in the prostate, ovaries, and lungs grow uncontrollably and turn into deadly cancers.