Eating two or more weekly servings of yoghurt is associated with lower risk of developing the adenomas which precede the development of bowel cancer – at least in men – found a large international study.
The observed associations were strongest for adenomas that are highly likely to become cancerous, and for those located in the colon rather than in the rectum, the findings indicate.
Previously published research has suggested that eating a lot of yoghurt might lower the risk of bowel cancer by changing the type and volume of bacteria in the gut (microbiome). But it's not been clear whether yoghurtintake might also be associated with a lower risk of pre-cancerous growths, known as adenomas.
The researchers at the Washington University School of Medicine in St Louis, Sun Yat-sen University, Guangzhou, China, Harvard TH Chan School of Health, Massachusetts General Hospital, Harvard Medical School, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Yale Cancer Centre, therefore looked at the diets and subsequent development of different types of adenoma among 32,606 men who were part of the Health Professionals Follow Up Study and 55,743 women who were part of the Nurses’ Health Study.
All the study participants had had a lower bowel endoscopy – procedure that enables a clinician to view the inside of the gut – between 1986 and 2012. And every four years, they provided detailed information on lifestyle and diet, including how much yoghurt they ate.
During the study period, 5,811 adenomas developed in the men and 8,116 in the women. Compared with men who didn't eat yoghurt, those who ate two or more servings a week were 19% less likely to develop a conventional adenoma.
This lower risk was even greater (26%) for adenomas that were highly likely to become cancerous, and for those located in the colon rather than in the rectum.
While no obvious association was seen for men with a potentially more dangerous type of adenoma (serrated), a trend towards reduced risk was seen for those measuring 1 or more cm, which is considered to be large.
No such associations between yoghurt intake and the development of adenomas were evident among the women.
This is an observational study, and as such, can't establish cause. Further research would be needed to confirm the findings and uncover the biology involved, emphasise the researchers. But the large number of people studied and the regular updates on diet and lifestyle factors add heft to the findings, they suggest.
By way of a possible explanation for what they found, the researchers point out that Lactobacillus bulgaricus and Streptococcus thermophilus, two bacteria commonly found in live yoghurt, may lower the number of cancer-causing chemicals in the gut.
And the stronger link seen for adenomas growing in the colon may partly be due to the lower acidity (pH) in this part of the gut, making it a more hospitable environment for these bacteria, they add.
Alternatively, yoghurt may have anti-inflammatory properties and may reduce the 'leakiness' of the gut as adenomas are associated with increased gut permeability, they suggest.
Davenport et al 1 underscored the urgent need to identify new modifiable factors for colorectal adenomas. A few studies2 3reported that higher yogurt intake may reduce the risk of colorectal cancer (CRC), potentially mediated by the gut microbiome. However, no study has yet evaluated the association between yogurt intake and precursors of CRC.
We prospectively evaluated the association between yogurt intake and risk of conventional adenoma and serrated lesion, among 32 606 men in the Health Professionals Follow-up Study (HPFS) and 55 743 women in the Nurses’ Health Study (NHS), who have undergone lower endoscopy between 1986 and 2012. These participants provided detailed information on demographics, lifestyle and diet including yogurt consumption every 4 years. Multivariable logistic regressions were used to calculate ORs and 95% CIs associated with cumulative average of yogurt intake. We examined the associations by adenoma type (conventional adenomas only, serrated lesions only or both), malignant potential (for conventional adenomas: high-risk (≥1 cm or with villous component or high grade/severe dysplasia, or ≥3 adenomas) vs low risk; for serrated lesions: ≥1 vs <1 cm) and anatomical site (proximal, distal or rectum).
We documented 5811 adenomas in men and 8116 adenomas in women. In men, compared with individuals without yogurt consumption, men who consumed ≥2 servings/week had a lower risk of conventional adenoma (multivariable OR=0.81, 95% CI=0.71 to 0.94, ptrend=0.01; table 1). This inverse association was more pronounced for adenomas with high malignant potential (OR=0.74, 95% CI=0.59 to 0.92, ptrend=0.01) than those with low risk (ptrend=0.25) (figure 1A). Also, stronger inverse associations were observed for colon (OR=0.82, 95% CI=0.70 to 0.95, ptrend=0.01) than for rectal adenomas (ptrend=0.95) (figure 1B). Overall, among men, no apparent association was observed for serrated lesions (ptrend=0.34), but a trend toward inverse association for lesions ≥1 cm was seen (OR=0.48, 95% CI=0.25 to 0.95, ptrend=0.04) (figure 1A). In women, no associations were observed for conventional adenomas and/or serrated lesions (table 1) or according to adenoma subtype or anatomical sites
Xiaobin Zheng, Kana Wu, Mingyang Song, Shuji Ogino, Charles S Fuchs, Andrew T Chan, Edward L Giovannucci, Yin Cao, Xuehong Zhang