NMU 154 – Dairy Milk and Breast Cancer
Nutrition / Natural Medicine Update No 154 (Feb 28, 2019)
with Dr. James Meschino
Topic: Milk Consumption Strongly Linked to Breast Cancer, But Not Yogurt, Cheese or Soymilk
Source: International Journal of Epidemiology (2020)
A major study from Loma Linda University has shown that intake of dairy milk is associated with a greater risk of breast cancer in women – up to 80% depending on the amount consumed. The study published in the International Journal of Epidemiology in February 2020 examined dietary intakes of nearly 53,000 North American women, all of whom were initially free of cancer and were followed for nearly eight years. The study also factored in demographics, family history of breast cancer, physical activity, alcohol consumption, hormonal and other medication use, breast cancer screening, and reproductive and gynecological history. By the end of the study period, there were 1,057 new breast cancer cases during follow-up. The study did not find a link between soymilk or soy products and the risk of breast cancer. In fact, in those who substituted soymilk for cow’s milk, there was a marked reduction in breast cancer risk. Many women are afraid of having soymilk and soy products, but study after study from human data show that it may, in fact, be protective.
Regarding the consumption of cow’s milk, the researchers explained that there was 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. As the researchers explained, “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%.” It didn’t seem to matter if the milk was high fat, low fat or non-fat milk. They were all associated with the same breast cancer risk. But of special note is the fact that the consumption of yogurt and cheese did not appear to increase the risk for breast cancer.
For a long time, I have advocated for the consumption of low-fat Greek yogurt and the inclusion of soy products in the diet, and I stand by that today. As the researchers stated, “This raises the possibility that dairy-alternate milk (like soymilk, almond milk, oat milk) may be an optimal choice.” This study, by the way, is consistent with the recent report suggesting that vegans but not lacto-ovo-vegetarians experienced less breast cancer than non-vegetarians.
What might be causing breast cancer from milk and meat consumption may be the presence of higher levels of the hormone, insulin-like growth factor-1 (IGF-1), which is thought to promote certain cancers. Many animals receive growth hormone treatment, which raises the animals IGF-1 (insulin-like growth factor -1) blood levels. When we drink the milk or eat the meat of these animals, we also ingest the IGF-1 hormone found in these foods. IGF-1 acts as a fertilizer, prompting our cells to divide at a faster rate, which increases the risk of genetic mutations that can cause cancer. In this case, breast cancer, as the speculation goes. In fermented dairy products like yogurt and cheese, the hormones are likely broken down in the fermentation process, making them a safer bet from a breast cancer standpoint. At least that is thinking of some experts.
So, I think the day is coming whereby dairy farming practices (i.e. the administration of growth hormones to optimize milk production) or the recommendations to the public about milk consumption are going to change. I think this study is quite meaningful and that the use of low-fat Greek yogurt should be your highest priority dairy choice. In addition, using soymilk, or almond milk or oat milk are emerging as safer substitutes than the use of cow’s milk regarding the breast cancer risk.
I have included the scientific references for this information in the text below.
1. Main Reference: Synnove Knutsen, Rawiwan Sirirat, Andrew Mashchak, Michael Orlich, Karen Jaceldo-Siegl, Gary E Fraser. Dairy, soy, and risk of breast cancer: those confounded milk. International Journal of Epidemiology, 2020. https://academic.oup.com/ije/advance-article-abstract/doi/10.1093/ije/dyaa007/5743492?redirectedFrom=fulltext
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