Analysis of data from two large prospective cohort studies suggests that regular, long-term yogurt consumption may be associated with reduced incidence of colorectal cancer containing Bifidobacterium, particularly in the proximal colon. The research followed 132,056 participants through 2016 and accumulated more than 3 million combined years of participant observation data.
The study, published in Gut Microbes, found a statistically significant differential association between yogurt intake and colorectal cancer incidence based on tumor Bifidobacterium status (P heterogeneity = .0002). For individuals consuming at least two servings/week of yogurt vs less than one serving/month, the multivariable-adjusted hazard ratios (HR) were 0.80 (95% confidence intervals [CI] = 0.50–1.28) for Bifidobacterium-positive tumors and 1.09 (95% CI = 0.81–1.46) for Bifidobacterium-negative tumors.
"Our findings suggest that long-term yogurt intake may lower the incidence of Bifidobacterium-positive proximal colorectal cancer (but not Bifidobacterium-negative subtype)," the researchers, led by Satoko Ugai of the Department of Pathology at Brigham and Women’s Hospital, and Harvard Medical School and the Department of Epidemiology at Harvard T.H. Chan School of Public Health, wrote.
The research utilized data from the Nurses' Health Study and Health Professionals Follow-up Study, which documented 3,079 incident colorectal cancer cases. Of these cases, 1,121 had available tissue Bifidobacterium data: 346 (31%) were Bifidobacterium-positive and 775 (69%) were Bifidobacterium-negative. The researchers used inverse probability weighting to adjust for potential selection bias as a result of tissue availability.
The investigators assessed yogurt consumption using validated food frequency questionnaires administered every 4 years, with a high correlation coefficient of 0.97 for yogurt intake validation. They calculated cumulative average intake using data from all prior questionnaire cycles to best capture long-term consumption patterns.
The protective effect appeared strongest for proximal colorectal cancers. Analysis showed "a trend of the association of yogurt intake with lower incidence of Bifidobacterium-positive proximal colorectal cancer (P trend = .06; the multivariable HR for yogurt consumption of ≥ 2 servings/week vs < 1 serving/month = 0.53; 95% CI = 0.27–1.06)."
The researchers hypothesized that yogurt's protective effects may relate to maintaining balanced intestinal microflora and barrier function. They noted that "SCFA [short-chain fatty acid]-producing Bifidobacterium can possess cancer suppression properties via antioxidant, anti-inflammatory, and immune activation effects."
Study limitations included reliance on self-reported dietary data and a predominantly non-Hispanic White study population. The researchers emphasized that their findings require replication in other populations and corroboration through experimental evidence.
One investigator reported receiving research funding from Janssen, and consulting fees from Nerviano Medical Sciences. Another is a consultant for Etiome Inc. This study was not funded by any of these commercial entities.
