A study published in the International Journal of Epidemiology by researchers at Loma Linda University Health in Loma Linda, California, evaluated the risk factor.
Researchers evaluated the dietary intakes and cancer risk of nearly 53,000 North American women. They were cancer-free at baseline and followed for about eight years. Dietary intakes were estimated using food frequency questionnaires, repeated 24-hour recalls and a baseline questionnaire that asked about demographics, family history of breast cancer, physical activity and more. By the study’s end, 1,057 new breast cancer cases were identified.
According to Gary E. Fraser, the first author of the study, consuming as little as 1/4 to 1/3 cup of dairy milk per day was associated with an increased risk of breast cancer of 30%. Those who drank one cup per day, the associated risk went up to 50%. The risk climbed to as high as 80% in those who drank two to three cups per day. It didn’t matter whether participants consumed full-fat milk or skimmed milk, the risk factor was similar.
What is the link between milk and breast cancer?
According to Fraser, a possible reason for the association between breast cancer and dairy milk could be the sex hormone content of milk as close to 75% of dairy herds are pregnant. How does that lead to breast cancer? Breast cancer is usually hormone-responsive. Consumption of dairy and other animal proteins has been many a times, linked to higher blood levels of the insulin-like growth factor-1 hormone, thought to promote certain cancers.
The silver lining here is that fermented dairy products can be eaten to reduce the risk of cancer. It is a good news that fermented dairy foods such as cheese and yogurt are not associated with any increased breast cancer risk. Consuming yogurt regularly has been linked with reduced risk for lung cancer and, in men, colorectal cancer. Fermented foods are believed to have positive effects on the microbiome, which helps in reducing the risk of cancer.