Yogurt, a fermented dairy food primarily containing live lactic acid bacteria, is widely considered to possess health-promoting effects. Probiotics such as yogurt are reported to be effective in the prevention of Clostridium difficile infection-related diarrhea and inflammatory bowel diseases. Data from long-term prospective studies suggest that yogurt intake reduces the risk of type 2 diabetes, cardiovascular disease mortality, and all-cause mortality. In addition, a recent meta-analysis has reported that yogurt intake is associated with a decreased risk of colorectal cancer.
Evidence indicates that probiotics such as yogurt may play a cancer-preventative role via their effect on the intestinal microbiota composition and/or intestinal barrier function. Among important probiotic bacterial strains in yogurt, Bifidobacterium is suggested to have a tumor-suppressive effect.
Researchers at Brigham and Women’s Hospital, Harvard Medical School in Boston, and Harvard T.H. Chan School of Public Health, Boston, MA, hypothesized that long-term yogurt intake might be associated with colorectal cancer incidence differentially by tumor subgroups according to the abundance of tumor tissue Bifidobacterium. To test this hypothesis, they utilized two large prospective cohort studies. (1) 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.
Evidence indicates that the anti-tumor potential of yogurt may be attributed to its role in maintaining a balanced intestinal microflora, which may contribute to smooth transit of intestinal contents, competitive exclusion of deleterious microbes, maintenance of intestinal barrier function, and productions of bioactive peptides and short-chain fatty acids (SCFA). SCFA-producing Bifidobacterium can possess cancer suppression properties via antioxidant, anti-inflammatory, and immune activation effects.
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. They hypothesized that this lower rate was driven by a change in the gut microbiome, including 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.
“Our study provides unique evidence about the potential benefit of yogurt,” emphasized Shuji Ogino, MD, PhD, senior study co-author. “This study 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.
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.
