Long-term yogurt consumption tied to decreased incidence of certain types of colorectal cancer

(Press-News.org) 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.

“Our study provides unique evidence about the potential benefit of yogurt,” said corresponding author Shuji Ogino, MD, PhD, the chief of the Program in Molecular Pathological Epidemiology in the Department of Pathology at Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system. Ogino is also an American Cancer Society Professor, a Professor at Harvard T.H. Chan School of Public Health, and an Affiliate Member of the Broad Institute of MIT and Harvard. “My lab’s approach is to try to link long-term diets and other exposures to a possible key difference in tissue, such as the presence or absence of a particular species of bacteria. This kind of detective work can increase the strength of evidence connecting diet to health outcomes.”

Ogino and colleagues – team OPTISTIMISTICC – are funded by Cancer Research UK through Cancer Grand Challenges, a research initiative co-founded by Cancer Research UK and the National Cancer Institute in the United States.  OPTIMISTICC aims to transform the understanding of how the microbiome contributes to disease development, progression and response to treatment. As part of this, Ogino’s team aims to define the risk factors and environmental exposures that individuals encounter through life which are behind the rise of early-onset colorectal cancer and ultimately develop strategies to reduce the burden of this type of cancer.

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.

“It has long been believed that yogurt and other fermented milk products are beneficial for gastrointestinal health,” said co-senior author Tomotaka Ugai, MD, PhD, of the Department of Pathology at the Brigham and the Department of Epidemiology at the Harvard T.H. Chan School of Public Health. “Our new findings suggest that this protective effect may be specific for Bifidobacterium-positive tumors.”

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.”

 

Authorship: In addition to Ogino, Ugai and Chan, Mass General Brigham authors include Satoko Ugai, Hidetaka Kawamura, Kota Arima, Kazuo Okadome, Qian Yao, Kosuke Matsuda, and Yuxue Zhong. Additional authors include Li Liu, Keisuke Kosumi, Tsuyoshi Hamada, Kosuke Mima, Hiroki Mizuno, Wendy S. Garrett, Mingyang Song, Marios Giannakis, Edward L. Giovannucci, and Xuehong Zhang.

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