A new study in the International Journal of Epidemiology. found that while there is no apparent connection between soy intake and breast cancer risk, dairy milk is connected with elevated incidents of breast cancer. The study followed women for almost 8 years, all of them cancer-free to start, asked them to fill out daily food logs and found that there is a clear connection between dairy intake and breast cancer.

The study looked at soy, dairy, and breast cancer over 7.9 years among 52,795 women in North America, and by the end of the study, there were 1,057 new breast cancer cases among the women, and a higher number of those cancers were among dairy milk drinkers.

So while most people avoid soy for fear that the plant-based estrogens will act as actual estrogens in the body, research has shown that soy may actually be protective, since in past studies a moderate amount of soy in the diet has been associated with lower risks of breast cancer.

After nearly 8 years in which the women in the study (29.7%  of whom were Black), kept food diaries every 24 hours to create a reliable track record of what they ate, the results were in. They then matched these dietary questionnaires with cancer cases and found that among the participants (mean age of 57) there were 1,057 new breast cancer cases during follow-up.

"No clear associations were found between soy products and breast cancer, independently of dairy," the study states. "However, higher intakes of dairy calories and dairy milk were associated" with the elevated risks, the study found. "Full fat and reduced-fat milks produced similar results."

There was no such elevated risk among women who consumed soy milk, according to the study, and the findings of cancer risk among dairy milk drinkers were the same whether the women were pre- or post-menopausal.

The study concluded: "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."

“Consuming as little as one-quarter to one-third cup of dairy milk per day was associated with an increased risk of breast cancer of 30 percent,” lead researcher Gary E. Fraser, PhD, of Loma Linda University explained. “By drinking up to one cup per day, the associated risk went up to 50 percent, and for those drinking two to three cups per day, the risk increased further to 70 to 80 percent.”

Breast cancer is considered a "hormonal' cancer, meaning it is receptive to estrogens in the body, so adding estrogens from dairy may be the reason for this increased risk. Dr. Neal Barnard, founder of the Physicians Committee for Responsible Medicine (PCRM) has proposed adding a warning label to cheese, warning consumers that eating cheese can raise the risk of breast cancer. Barnard has written a book about why cheese is addictive, called The Cheese Trap, since it contains casein which acts on our opiate receptors, so while cheese has the same hormonal risk as milk, it's difficult to quit. Barnard also wrote a book called Your Body In Balance, about the dangers of hormones in your food and how they wreak havoc with your menstrual cycle and reproductive health.

What most consumers don't know, is that breast cancer, ovarian cancer, uterine cancer and prostate cancer are all hormonally sensitive cancers, so while this study only looked at breast cancer they may all be affected by adding estrogens to our diet. Drinking milk may elevate the risk for other types of cancer, sincee if milk drives up the risk for that cancer, it may also increase the risk for other hormonal cancers, according to experts.


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