Associations between soy, dairy intakes and breast cancer risk are inconsistent. Dairy has even been tied to decreased risk for breast cancer, according to the World Cancer Research Fund. A new observational study shows contrary results.

The researchers have found that drinking milk increases the risk of developing breast cancer. The study suggests that milk raises breast cancer risk, and the more you drink the higher your risk may be.

"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%," first author Gary E. Fraser, MBChB, PhD, said in a press statement. Fraser is affiliated with the School of Public Health at Loma Linda University, California.

"By drinking up to 1 cup per day, the associated risk went up to 50%, and for those drinking 2 to 3 cups per day, the risk increased further to 70% to 80%," he added.

The findings have been published in the International Journal of Epidemiology.

The study cohort contains 52 795 North American women, initially free of cancer, followed for 7.9 years. Women had a mean age of 57.1 years.

Dietary intakes were estimated from food frequency questionnaires from six structured 24-h dietary recalls. Incident invasive breast cancers were detected mainly by matching with cancer registries. For 1011 women, researchers double-checked food intake with 24-hour diet questionnaires and verified soy intake by analyzing urine levels of soy isoflavones. Analyses used multivariable proportional hazards regression.

Data on invasive breast cancer diagnoses came from national registries in the US and Canada. Over the course of 7.9 years, 1057 women developed invasive breast cancer. Results were adjusted for a range of factors related to breast cancer risk, including diet, lifestyle, and family history of breast cancer.

Overall, women who consumed the most calories from dairy per day had 22% increased risk for breast cancer, compared with women with the fewest calories from dairy (hazard ratio, 1.22; 95% confidence interval, 1.05-1.40; P = .008). Women who drank the most cow›s milk per day had 50% increased risk for breast cancer compared with women who drank the least.

Drinking full or reduced-fat cow's milk did not change the findings.

The researchers concluded that Higher intakes of dairy milk were associated with greater risk of breast cancer when adjusted for soy intake. Current guidelines for dairy milk consumption could be viewed with some caution.No significant association was found between breast cancer risk and cheese or yoghurt consumption.

Current guidelines recommend that adults and children aged 9 and over drink three 8 oz glasses of milk per day, or equivalent portions of yoghurt, cheese, and other dairy products.

For further reference log on to :

International Journal of Epidemiology, dyaa007, https://doi.org/10.1093/ije/dyaa007