Potential synergistic effect with greater consumption of both

by Ian Ingram, Deputy Managing Editor, MedPage Today
October 24, 2019

Consuming more yogurt and fiber may protect against lung cancer development, a global study of nearly 1.5 million adults suggested.

After adjustment for various known risk factors, individuals who ate higher amounts of yogurt — roughly 3 oz per day for men and 4 oz per day for women — had 19% lower risk of lung cancer compared to non-yogurt eaters (HR 0.81, 95% CI 0.76-0.87), reported Xiao-Ou Shu, MD, PhD, of Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues.

For fiber, people in the highest intake quintile had a 17% reduced lung cancer risk versus those in the lowest intake quintile (HR 0.83, 95% CI 0.76-0.91), as described in JAMA Oncology.

“High consumption of fiber (prebiotics) and yogurt (probiotics) was related to a low risk of lung cancer. This association pattern was consistently seen among current, past smokers, and never smokers,” Shu told MedPage Today. “In addition to the known cardiovascular benefit of fiber and yogurt intake, physicians now have additional justification to encourage their care population to increase their consumption of these two types of healthy diet.”

Combined, the two were associated with an even greater effect on lung cancer risk reduction, with those in the highest fiber intake quintile and high yogurt eating group having a 33% reduced risk (HR 0.67, 95% CI 0.61-0.73), an advantage in all smoking categories:

• Current: HR 0.74 (95% CI 0.67-0.83)
• Former: HR 0.66 (95% CI 0.59-0.73)
• Never: HR 0.69 (95% CI 0.54-0.89)

“In this large pooled analysis, after adjusting for a wide range of known or putative lung cancer risk factors, we found that dietary fiber and yogurt consumption were both associated with reduced risk of lung cancer,” Shu’s group wrote. “For the first time to our knowledge, a potential synergistic association between fiber and yogurt intakes on lung cancer risk was observed.”

Their results on fiber counter those from the U.K. Million Women Study, which found no association between increasing fiber intake and lung cancer risk in never smoking women. And they follow on the heels of a recent study on yogurt’s potential impact on colon cancer development in men. Compared with those who consumed no yogurt, men who ate at least two servings of yogurt per week had a 19% lower risk for conventional polyps, and a 26% lower risk for polyps with higher malignant potential. The same association was not observed among women in that study.

“The health benefits of fiber and yogurt may be rooted in their prebiotic and probiotic properties, through which they independently or synergistically modulate gut microbiota,” Shu’s team suggested. “There are high expectations that yogurt may help prevent lung diseases; in vivo and in vitro studies have shown that some probiotic strains inhibit lung metastasis, enhance natural killer cell activity, and have antitumor and anti-inflammatory activities.”

For their study, the researchers analyzed data on 1,445,850 adults (57% women, mean age 57.9 years) from 10 cohort studies in the U.S., Europe, and Asia – including the Health Professionals Follow-up Study; Nurses’ Health Study; Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial; and others.

With median follow-up of 8.6 years, there were 18,822 cases of lung cancer. Median fiber intake was 18.4 g per day, and median yogurt intake among the 62.2% that reported eating the dairy product was 23.3 g per day. In general, high fiber and yogurt eaters were more likely to have received a college degree, were less likely to smoke, consumed less alcohol, and were more physically active.

In the high yogurt groups, men ate an average of 82.5 g per day versus 111.1 g per day for women, though lower amounts of yogurt consumption were also associated with reduced lung cancer incidence (HR 0.85, 95% 0.81-0.90). Greater mean fiber intake was as well, as seen with individuals in the third (HR 0.87, 95% CI 0.81-0.94) and fourth quintiles (HR 0.85, 95% CI 0.80-0.90) of fiber intake.

Previous research from Shu and colleagues using this same study population demonstrated an association between higher saturated fat intake and increased lung cancer risk, and this served as one of the variables adjusted for in their analysis. Others included smoking status, pack-years, and other common risk factors for lung cancers.

“The large sample size of our study allowed us to adjust for these correlated dietary and non-dietary factors in the statistical analyses,” said Shu. “The association of fiber/yogurt intake with lung cancer we found in our study, thus, is independent from fat intake.”

The association for a reduced risk of lung cancer remained significant in never smokers, and regardless of sex, race, and lung tumor histology — associations were stronger for the main findings in individuals under age 57 and in drinkers.

LAST UPDATED 10.24.2019