A new study published in the International Journal of Epidemiology has found that the intake of milk could be the cause of breast cancer in women.
Gary E Fraser, from the School of Public Health, Loma Linda University, and team found that drinking even one glass of milk could be linked with breast cancer development in women.
Breast cancer can develop in either or both breasts. It feels like a lump and could be seen with the help of an X-ray. Many of the lumps are benign (non-cancerous) but need proper medical examination so that the growth and type could be monitored. In 2018, 627,000 women died of breast cancer, according to World Health Organization. 50% of them belonged to developed whereas 50% were from under developed countries.
This cohort study included 52,795 North American women who were initially cancer-free and were followed up for eight years when they got diagnosed with breast cancer. The diagnosis was made by matching cancer registries. Dietary patterns were assessed by the help of Food Frequency Questionnaires and six structured 24hour dietary recall.
As many as 1,057 new breast cancer cases appeared in the eight-year study. The results got ugly when increased intake of dairy milk and calories got associated with high breast cancer risk. Association with cheese and yogurt was low. Full fat and low milk showed a higher association. However, the association of soy products with cancer was unclear.
Gary E. Fraser, the first lead author of the paper, says, “There is fairly strong evidence that either dairy milk or some other factor closely related to drinking dairy milk is a cause of breast cancer in women. 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%. By drinking up to one cup per day, the associated risk went up to 50%, and for those drinking two to three cups per day, the risk increased further to 70% to 80%.”
Fraser also explained that this association of breast cancer with milk could be because of the sex hormones present in dairy milk as (up to 75%) cows are mostly pregnant and lactating. Excess consumption of animal protein is also linked with increased hormone production of insulin-like growth factor-1 (IGF-1) which could cause cancer. More work is required to further explore these factors.
The findings contradict American Dietary Association’s milk recommendations that say you should drink up to three cups of fat-free or low-fat milk daily. It is better to choose low-fat milk products instead of full fat.
The research has startled many because milk is considered the healthiest food in the world. One cup of low-fat milk provides 140 calories with fat 5g, carbohydrates 13 g, sugar 11g and protein 8g. Milk is an excellent source of calcium, vitamin D, phosphorus, riboflavin, vitamin B12, selenium, potassium and zinc. Decreasing the intake of milk means lowering the levels of essential macro and micro nutrients that are needed for bones and human body.
Many studies conducted in the past go against these findings and state that dairy intake is inversely related to breast cancer development in females depending on the dose, type and period.