Higher dairy milk intake may promote breast cancer

Consuming high amounts of dairy milk and calories from dairy appears to contribute to an increased risk of developing breast cancer, a study has found.

Researchers followed 52,795 women (mean age, 57.1 years), who were initially free of cancer, for 7.9 years. They estimated dietary intakes from food frequency questionnaires, as well as from six structured 24-h dietary recalls in 1,011 women included in the calibration study. Incident invasive breast cancers were identified through cancer registry linkage.

There were 1,057 new breast cancer cases documented during follow-up. Multivariable proportional hazards regression models showed no clear associations between soy products and breast cancer, independently of dairy.

However, 90th vs 10th percentiles of intakes of dairy calories and dairy milk were associated with a risk increase. The respective hazard ratios (HRs) were 1.22 (95 percent confidence interval [CI], 1.05–1.40) and 1.50 (95 percent CI, 1.22–1.84). Results were similar for full fat and reduced fat milks, whereas no significant relationships were noted for cheese and yogurt.

When median intakes of dairy milk were replaced with soy milk, the risk of breast cancer was attenuated (HR, 0.68, 95 percent CI, 0.55–0.85).

Similar-sized associations were noted among pre- and postmenopausal breast cancer cases, with CIs also excluding the null in oestrogen receptor (ER+, ER–) and progesterone receptor (PR+) cancers.

In light of the findings, researchers pointed out that current guidelines for dairy milk consumption should be viewed with some caution.