Drinking dairy milk can cause breast cancer. The chances could increase by as much as 80 percent if you’re drinking two to three cups of milk everyday.

Even drinking just a quarter of a cup of milk every day raises the risk my 30 percent, a team from Loma Linda University in California has discovered, and they say their research has uncovered ‘fairly strong evidence that dairy milk is a cause of breast cancer in women.’

They looked at the dairy consumption of 53,000 women who were cancer-free at the start of the study, and 1,057 of them went on to develop breast cancer over the next eight years.

Although the researchers couldn’t see a link to soymilk and other soy products, they found a strong connection to dairy milk, but not to other products such as yoghurt and cheese. The risk was the same whether the women were drinking low-fat or full-fat milk.

The risk increased with the amount of milk the women were drinking every day. Those drinking as little as a quarter of a cup had a 30 percent increased risk, while one full cup caused a 50 percent raised risk, and it went up to as much as 80 percent for the women drinking two to three cups a day.

The researchers aren’t sure why milk is a carcinogen, but they think it could be due to the sex hormone content of the milk. The cows are lactating, and around 75 percent of the herd could be pregnant at any one time. Dairy also promotes the hormone IGF-1 (insulin-like growth factor -1) in the blood, which is known to promote cancer.

Int J Epidemiol, 2020; dyaa007