Their extensive analysis of 53,000 North American women yielded an 80% breast cancer increase associated with habitual dairy milk consumption.
“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%,” explained the study’s first author Gary E. Fraser, MBChB, PhD, in a press statement. “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%.”
These findings are discordant with the recommended daily value issued by The United States Department of Agriculture.
The USDA advises adults to consume three servings of dairy products per day, and children to consume around two or two and a half servings per day. Dairy servings are quantified based on source, i.e: one cup of milk, one cup of yogurt, one ounce of hard cheese and half a cup of cottage cheese all qualify as a single serving.
“Evidence from this study suggests that people should view that recommendation with caution,” Fraser continued.
As posited by the new paper, even the lower end of routine dairy intake poses serious health risks;though no notable association was found in respect to soy products.
“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.”
For eight years Fraser and his team tracked the dairy intake of 53,000 women via food frequency questionnaires (FFQ), and repeated 24 hour recalls. All of the participants were cancer-free at the start of the study.
With the help of a baseline survey, the researchers were able to factor demographics, family history of breast cancer, degree of physical activity, alcohol consumption, medication use, frequency of breast cancer screenings, and reproductive and gynecological history, into their final analysis.
By the end of the eight-year study period 1,067 new breast cancer cases appeared. Although no adverse correlations were found between soy products and breast cancer, independent of dairy, low-fat milk intimated the same negative associations as full fat-milk as far as breast cancer risk was concerned.
More research would need to be conducted to conclude anything categorical but Fraser believes non-dairy milk substitutes could drastically reduce the risk observed in the new report.
The finds documented in the most recent Adventist Health Study are inline with this prediction. That particular review determined that vegans (not including lacto-ovo-vegetarians) develop breast cancer significantly less often than non-vegetarians.
It’s too early to identify all of the mechanisms at play but Fraser suspects the concentration of sex hormones present in dairy milk might be a contributing factor. Previously conducted literature has established a robust relationship between consuming animal proteins and the development of hormone-responsive cancers.
Until a follow-up analysis is conducted non-dairy milk appears to be the best source for calcium, phosphorus, and B vitamins. Be sure to read through our detailed ranking of the most popular variations.
“Dairy milk does have some positive nutritional qualities,” Fraser said, “but these need to be balanced against other possible, less helpful effects. This work suggests the urgent need for further research.”
The new study, titled Dairy, soy, and risk of breast cancer: those confounded milks. was co-authored by Synnove Knutsen, Rawiwan Sirirat, Andrew Mashchak, Michael Orlich, Karen Jaceldo-Siegl, and Gary E Fraser.
The entire report can be read in The Journal of Epidemiology.