Eating two or more weekly servings of yogurt may help to lower the risk of developing the abnormal growths (adenomas) which precede the development of bowel cancer--at least in men--finds research published online in the journal Gut.
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 yogurt 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 yogurt intake might also be associated with a lower risk of pre-cancerous growths, known as adenomas.
The researchers 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--a 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 yogurt they ate.
During the study period, 5811 adenomas developed in the men and 8116 in the women.
Compared with men who didn't eat yogurt, 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 yogurt 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 yogurt, 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, yogurt may have anti-inflammatory properties and may reduce the 'leakiness' of the gut as adenomas are associated with increased gut permeability, they suggest.
Peer reviewed? Yes
Evidence type: Observational