Some foods are considered good for the gut microbiome. Yogurt, which is loaded with beneficial bacteria, is one of them. A recent study found that eating yogurt two or more times a week for long periods of time (years!) is associated with a lower risk for several types of colorectal cancer.
However, it must be noted that the study found that eating yogurt, whether frequently or not, did NOT have an association with overall colorectal cancer incidence. It was just with colon cancer that had Bifidobacterium-positive tumors (31% of colon cancers in this study). Persons eating 2 or more yogurts per week had a 20% lower incidence of Bifidobacterium-positive tumors.
Yogurt contains Bifidobacterium bacteria, a bacteria that is considered tumor-suppressive. By the way, all fermented dairy products (e.g., kefir, buttermilk, cheese) have long been viewed as beneficial to health, and they all contain a variety of microbes, including Lactobacillus species.
From Science Daily: Long-term yogurt consumption tied to decreased incidence of certain types of colorectal cancer
Yogurt, which contains live strains of bacteria, is thought to protect against many types of diseases, with some reports indicating it could reduce risk of colorectal cancer.
A new study led by investigators from Mass General Brigham finds that yogurt consumption over time may protect against colorectal cancer through changes in the gut microbiome. Using data from studies that have followed participants for decades, researchers found that long-term consumption of two or more servings per week of yogurt was tied to lower rates of proximal colorectal cancer positive for Bifidobacterium, a bacterial species found in yogurt.
The study showed that the bacterial species was quite common: about 30 percent of patients with colorectal cancer had detectable Bifidobacterium in their tumor tissue. Their results are published in Gut Microbes.
To conduct their study, the researchers used data from two U.S.-wide prospective cohort studies known as the Nurses' Health Study (NHS) and the Health Professionals Follow-up Study (HPFS). The studies have followed more than 100,000 female registered nurses and 51,000 male health professionals, respectively. Participants have been followed since 1976 for the NHS and 1986 for HFPS, answering repeated questionnaires about lifestyle factors and disease outcomes, including questions about average daily intake of plain and flavored yogurt, as well as other dairy products. The researchers also assessed tissue samples for participants with confirmed cases of colorectal cancer, measuring the amount of Bifidobacterium DNA in tumor tissue.
The researchers found 3,079 documented cases of colorectal cancer in the two study populations. Information on Bifidobacterium content was available in 1,121 colorectal cancer cases. Among those, 346 cases (31%) were Bifidobacterium-positive, and 775 cases (69%) were Bifidobacterium-negative. The researchers did not observe a significant association between long-term yogurt intake and overall colorectal cancer incidence, but they did see an association in Bifidobacterium-positive tumors, with a 20 percent lower rate of incidence for participants who consumed two or more servings of yogurt a week. This lower rate was driven by lower incidence of Bifidobacterium-positive proximal colon cancer -- a type of colorectal cancer that occurs in the right side of the colon. Studies have found that patients with proximal colon cancer have worse survival outcomes than patients with distal cancers.
The researchers hypothesize that long-term yogurt intake may reduce risk of proximal colon cancer by changing the gut microbiome, including Bifidobacterium, but they note that further research that brings together both basic science and population health studies is needed to draw a definitive conclusion.
"This paper adds to the growing evidence that illustrates the connection between diet, the gut microbiome, and risk of colorectal cancer," said co-author Andrew T Chan, MD, chief of the Clinical and Translational Epidemiology Unit at Massachusetts General Hospital, a founding member of the Mass General Brigham healthcare system and co-lead for Cancer Grand Challenges team PROSPECT addressing causes of cancer in young adults. "It provides an additional avenue for us to investigate the specific role of these factors in the risk of colorectal cancer among young people.