Milk and Cancer: Myths and Reality

It is known that cow milk contains many different hormones necessary for the rapid growth and development of calves (2015) year. Among them are prolactin, progesterone, insulin-like growth factor, prostaglandins, and estrogens. Practically all of them are not destroyed by heating, so they are present in milk and dairy products. Good news — their quantity is comparatively not as high as researchers claim — for example, three servings of whole milk contain about one-tenth of the amount of estrogens that could potentially have any physiological effect on our body.

A larger number of authors of numerous studies and reviews lean toward the view that there is no link between dairy product consumption and the risk of cancer, or, conversely, that it is inversely proportional.

What exactly do they write?

A review (2018) year, devoted to the impact of dairy product and red meat consumption on chronic diseases, states that there is no link between dairy consumption and the development of breast cancer.

In another study (based on 80,000 patients, Norway, 2018), a "weak inverse relationship between milk consumption and the development of colon cancer in women" was shown (let us recall that in Northern Europe most people have working lactase).

In a review (2016) it is shown that consumption of dairy products did not influence or reduced the risks of developing type 2 diabetes, obesity in children, heart diseases, with a noted positive effect on mineralization and bone density. It indicates the existence of an inverse relationship between milk consumption and the risk of developing colon cancer, bladder cancer, stomach cancer, and breast cancer, and the absence of a link with the risk of pancreatic cancer, ovarian cancer, and lung cancer. The authors note that the evidence linking milk consumption to prostate cancer risk is inconsistent.

Other authors (2018) also support them in this regard and agree that "there is no clear data on milk consumption and cancer risk."

In a small section of the aforementioned review from 2015, they state that "the available data in the literature are very controversial." Some authors point to a link between milk consumption and prostate cancer risk. In particular, Japanese researchers are decidedly inclined, linking a substantial increase in the incidence of this disease among men with nearly a 20-fold increase in the volume of dairy product consumption.

The authors of a review, published in 2017 based on an analysis of 172 publications on milk and the risk of developing tumors of the prostate, indicate that such a link likely exists, and suggest that the insulin-like growth factor plays a key role here.

Other researchers have studied the effect of milk on the growth of cultures of prostate and breast cancer cells. They showed that milk promoted the growth of prostate cancer cells but did not affect the growth of breast cancer cells (its rate was slightly increased by soy milk — oops).

Just in case, note that results from "in vitro" studies (i.e., outside the body) are not equivalent to the statement that "product X causes cancer"!

In one publication (2018) 61 studies were analyzed and shown that fermented dairy products (i.e., fermented milk products) actually reduce the risk (by about 15%) of developing cancers (specifically studied were the links with esophageal cancer, bladder cancer, and colon cancer).

In a recent study (2018) (2258 people, Northern California and Louisiana, diagnosis — prostate adenocarcinoma, patient age 40-79) the patient's diet in the year before diagnosis was analyzed. It showed that the disease progression was more aggressive among whole milk drinkers: "when analyzing the aggressiveness of prostate cancer among consumers of whole and skim milk, it was noted that consuming more than 1.25 servings of whole milk increased the chances of highly aggressive prostate cancer by 74% compared to skim milk consumers). It is fair to note that this study also points to other factors that correlate with the disease, such as smoking and saturated fat consumption.

Similar results were obtained earlier by other authors (2013, 2806 patients), where the consumption of whole milk was associated with higher mortality from prostate cancer.

Another study (2017, Sweden, 525 people) showed that among men who were diagnosed with adenocarcinoma and who consumed more than three servings of high-fat milk, death rates were higher.

What conclusions should be drawn from this?

There are no scientific data that dairy products cause cancer. However, there is evidence of a decreased probability of developing certain types of cancer (gastric, colon, bladder, breast) with the consumption of fermented dairy products.

There are conflicting data about the effect of milk (especially whole milk) on the development of prostate cancer. Therefore, consumers who are in a risk group (for example, men with chronic prostatitis or diagnosed prostate cancer, or those with a family history) should probably plan their diet more carefully — not exceed recommended milk intake, favor fermented dairy products and milk with lower fat content.