Many people (even health professionals) are still under the impression that dairy products made from milk are unhealthy. NOT TRUE. Consuming dairy products, especially whole milk products, is associated with a number of health benefits.
Recent research adds to the growing body of research finding that higher intake of dairy products is associated with a lower risk of colorectal cancer (commonly referred to as colon cancer). One big review found a 20% decrease in colon cancer with higher dairy product consumption, and an 18% decrease in colon cancer specifically with higher milk consumption.
The researchers discussed studies that found that with each 400 g (about 1 3/4 cups) of dairy foods that people consumed daily, there was a 13% reduced risk of colorectal cancer.
It's more than the calcium found in the dairy products (there is research already finding that calcium in foods is associated with lower risk of colorectal cancer). And it's more than dairy products that are fermented (e.g., yogurts). It's high fat milk products (whole milk) that have the highest association. But currently it's unclear why.
Excerpts from Medscape: Does Higher Dairy Intake Reduce CRC Risk?
Two recent studies have added to the growing body of research suggesting consuming more dairy reduces a person’s risk of getting colorectal cancer.
A prospective cohort study in Nature Communications published in January looked at the incidence of colorectal cancer (CRC) in more than 540,000 UK women over 16 years and found a 14% reduced risk for the cancer for every 200 g of dairy milk consumed per day. It also found an 8% reduced risk per 50 g of yogurt per day.
The other study, from GutMicrobes, also published in January, looked specifically at yogurt intake with a focus on Bifidobacterium, a bacteria commonly found in yogurt. The researchers found that people who had at least two servings per week of yogurt had a 20% lower risk for Bifidobacterium-positive tumors than those who had less than one serving per month of yogurt, “suggesting the antitumor effect of yogurt intake on the specific tumor subgroup.”
Together, these studies and other recent systematic reviews raise questions about whether dairy foods or fermented dairy foods in particular reduce CRC risk independent of the calcium they provide. The association between higher dietary calcium and lower CRC risk has a longer, more established research base, but it’s possible there are other aspects of dairy foods in addition to calcium that provide some benefit.
“Traditionally, when we’ve thought of colorectal cancer, we’ve associated it with the dietary factors of alcohol and red and processed meat on the negative side, and whole foods on the positive side, essentially fruits, nuts, vegetables, etc.,” said Christopher J. Damman, MD, MA, a clinical associate professor of gastroenterology at the University of Washington Medicine, Seattle. “The dairy factor is a little bit new.”
Earlier Research on Dairy Intake
A 2019 systematic review and meta-analysis in Advances in Nutrition included more than 22,000 participants from 15 cohort studies and 14 case-control studies looking at associations between dairy intake and CRC risk. The cohort studies found a 20% lower risk for CRC with higher consumption of dairy products overall (relative risk [RR], 0.80; P < .01) and an 18% reduced risk specifically with higher milk consumption (RR, 0.82; P < .01) compared with lower consumption. The risk was substantially lower for high-fat dairy products (RR, 0.68; P < .01). Meanwhile, a 9% reduced risk for low-fat dairy products (RR, 0.91; P = .22) was not significant, neither was a 10% reduced risk for fermented dairy products (RR, 0.9; P = .32); however, only four studies looked at fermented dairy products. In the case-control studies, only total milk intake was significantly associated with a reduced risk (RR, 0.85; P = .03) while other products had no statistically significant associations.
An earlier 2017 systematic review and meta-analysis, published in the Annals of Oncology by scientists at the World Cancer Research Fund, found “pretty consistent” trends in reduced cancer risk with any dairy intake across Europe, the United States, and Asia, noted Anne McTiernan, MD, PhD, a professor of epidemiology at Fred Hutch Cancer Center, Seattle. For each additional 400 g of dairy foods people consumed per day, they had a 13% reduced risk for CRC.
A 2022 systematic review and meta-analysis in Frontiers in Nutrition exclusively looked at yogurt consumption and CRC risk in 16 studies and found a modestly reduced risk overall (OR, 0.87), with a greater reduction seen in the case-control studies (OR, 0.75) than the cohort studies (OR, 0.91). These results go along with similar findings showing a decreased risk for CRC with fermented dairy foods more broadly seen in a 2019 meta-analysis published in the International Journal of Cancer. ...
The Role of Calcium in Dairy
The link between optimal calcium intake and reduced CRC risk is well-established, said William Grady, MD, a professor and medical director of the Gastrointestinal Cancer Prevention Program at Fred Hutch Cancer Center in Seattle.
The recent Nature Communications study found a 17% reduced risk associated with each additional 300 mg/d of calcium intake. In comparing how strongly different factors correlated with each other, dairy milk was more strongly correlated with calcium than yogurt, but calcium intake did not appear to entirely explain the reduced risk for either milk or yogurt.
“These findings [of the Nature Communications study] underscore the multi-faceted role that diet plays in colon cancer development and show that calcium-rich foods like dairy are key players in colorectal cancer risk reduction,” said Anam Khan, MD, an assistant professor of gastroenterology, hepatology, and nutrition at The University of Texas MD Anderson Cancer Center in Houston. “Colon cancer is the third most commonly diagnosed cancer among all cancers and the second leading cause of cancer-related death in the United States,” she said. The population at large could benefit from ensuring their diet includes good amounts of dairy, Khan said, adding that 300 mg is the amount of calcium in a single 8-oz glass of milk, “so really, just taking a glass of milk a day will provide that benefit.”
Rashmi Verma, MD, an associate professor of medical oncology at the University of California Davis, noted that other components in dairy, such as conjugated linoleic acid, butyric acid, and sphingomyelin, have been shown to inhibit growth of some CRC cells in animal studies. Grady also noted investigation into other proteins in dairy that may be related to the lower CRC risks, but that research remains preliminary and incomplete, making it difficult to tell whether the reduced risk in dairy is mostly calcium-related or derives from other dairy components.
Microbiome Health As a Mechanism
Meanwhile, the Gut Microbes study raises questions about whether effects on the microbiome from fermented dairy products plays a role in reduced risk, but less research exists to support this possibility, Grady said.
Still, the study raises questions about ways in which dairy products, particularly fermented ones, may impact the gut microbiome in ways that modestly affect CRC risk. Understanding the interactions of the gut microbiome and cancer is still “relatively uncharted territory” where data is accruing but still evolving, Verma said.