By Lisa Rapaport

(Reuters Health) – Even among smokers, people who eat more fiber and yogurt may be less likely to develop lung cancer than those who don’t consume much of these foods, a research review suggests.

Researchers examined pooled data from 10 previous studies that included a total of almost 1.45 million adults in Asia, Europe, and the United States. After following people for an average of 8.6 years, 18,822 cases of lung cancer were documented.

Compared to people who never ate yogurt, those who consumed the most yogurt were 19% less likely to develop lung cancer, the analysis found.

People who had the most fiber in their diets, meanwhile, were 17% less likely to develop lung cancer than those who ate the least fiber.

And individuals with the highest fiber intake and highest yogurt consumption were 33% less likely than those with the lowest consumption of both to develop lung cancer, the study team reports in JAMA Oncology.

“Our study suggests a potential novel health benefit of increasing dietary fiber and yogurt intakes in lung cancer prevention,” senior study author Dr. Xiao-Ou Shu of Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues write.

While the study wasn’t a controlled experiment designed to prove yogurt or fiber protects against lung cancer, it’s possible these kinds of foods might lead to changes in the gut microbiota – the bacteria living in our digestive tract – that help protect against cancer, the study authors hypothesize.

It’s also possible fiber and yogurt might help protect against inflammation, which in turn helps reduce the potential for tumors to develop, the researchers note.

Fiber-rich foods typically have lots of prebiotics, nondigestable compounds that can be fermented in the gut and serve as food for beneficial bacteria, the authors note. Yogurt has lots of those beneficial bacteria, or probiotics.

Considerable research links the gut microbiota to the immune system overall. And some recent studies have suggested that the gut microbiota may play a role in lung inflammation, the study authors point out.

The reduced risk of lung cancer associated with fiber and yogurt in the study persisted even after researchers accounted for smoking habits.

For people who never smoked, the lung cancer risk reduction associated with the highest levels of yogurt and fiber consumption was 31%, while for smokers it was 24% and for former smokers, 34%.

The researchers point out that they didn’t know what type of fiber people consumed or which types of foods they ate to get their fiber, or the type or fat content of any yogurt people ate.

They also lacked data on some other risk factors for lung cancer, including low income or limited education levels as well as any history of chronic obstructive pulmonary disorder.

Even so, the authors conclude it’s worth considering the potential protective effect of yogurt and fiber.

“For the first time to our knowledge, a potential synergistic association between fiber and yogurt intakes on lung cancer risk was observed,” the study authors write. “Although further investigation is needed to replicate these findings and disentangle the underlying mechanisms, our study suggests a potential novel health benefit of increasing dietary fiber and yogurt intakes in lung cancer prevention.”

SOURCE: JAMA Oncology, online October 24, 2019.