Long-term yogurt intake may protect against the development of colorectal cancer through changes in the gut microbiome, according to a recent study published by Ugai et al in Gut Microbes.
Background
Yogurt—which contains live strains of bacteria—is thought to protect against many types of diseases. Bifidobacterium is a bacterial species found in yogurt.
Study Methods and Results
In this study, investigators used data from the Nurses’ Health Study and the Health Professionals Follow-up Study, involving more than 100,000 female registered nurses since 1976 and 51,000 male health professionals since 1986, respectively. The participants were asked to complete repeated questionnaires about their lifestyle factors and disease outcomes, including questions regarding their average daily intake of plain and flavored yogurt as well as other dairy products. The investigators also assessed tissue samples from the participants with confirmed cases of colorectal cancer, measuring the amount of bifidobacterium DNA in their tumor tissue.
“[Our] approach [was] 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,” explained co–senior study author Shuji Ogino, MD, PhD, Professor at the Harvard T.H. Chan School of Public Health, Chief of the Program in Molecular Pathological Epidemiology in the Department of Pathology at the Brigham and Women’s Hospital, and an affiliate member of the Broad Institute of the Massachusetts Institute of Technology and Harvard University.
The investigators identified 3,079 documented cases of colorectal cancer in the two study populations. Information on the presence of bifidobacterium was available in 1,121 of the colorectal cancer cases. Among them, 31% (n = 346) of the patients had bifidobacterium-positive colorectal cancer and 69% (n = 775) had bifidobacterium-negative colorectal cancer. Although there were no statistically significant associations between long-term yogurt intake and overall colorectal cancer incidence, there was a correlation in bifidobacterium-positive tumors. The investigators found that long-term consumption of two or more servings of yogurt per week was linked to a 20% lower rate of bifidobacterium-positive colorectal cancer. This lower rate was driven by a lower incidence of bifidobacterium-positive proximal colorectal cancer. Previous studies have demonstrated that patients with proximal colorectal cancer may experience poorer survival outcomes compared with patients with distal colorectal cancer.
Further, the investigators revealed that the bacterial species was common. About 30% of the patients with colorectal cancer had detectable levels of bifidobacterium in their tumor tissue.
Conclusions
“Our study provides unique evidence about the potential benefit of yogurt,” emphasized Dr. Ogino. The investigators hope their findings can help transform the understanding of how the microbiome may contribute to disease development, progression, and response to treatment. They plan to continue defining the risk factors and environmental exposures that individuals encounter through life that may lead to the rise of early-onset colorectal cancer as well as develop strategies to reduce the burden of the disease.
“It has long been believed that yogurt and other fermented milk products are beneficial for gastrointestinal health,” detailed co–senior study author Tomotaka Ugai, MD, PhD, of the Department of Pathology at the Brigham and Women’s Hospital 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 [to] bifidobacterium-positive tumors,” he added.
The investigators hypothesized that long-term yogurt intake may reduce the risk of proximal colorectal cancer by changing the gut microbiome, including bifidobacterium. However, they underscored, further research that brings together both basic science and population health studies may be needed to draw a definitive conclusion.
“This paper adds to the growing evidence that illustrates the connection between diet, the gut microbiome, and [the] risk of colorectal cancer,” underscored co–study author Andrew Chan, MD, Chief of the Clinical and Translational Epidemiology Unit at Massachusetts General Hospital and Co-Lead of the Cancer Grand Challenges team PROSPECT. “It provides an additional avenue for us to investigate the specific role of these factors in the risk of colorectal cancer among young [patients],” he concluded.
Disclosure: For full disclosures of the study authors, visit tandfonline.com.
