More than 11 million Americans suffer from chronic obstructive pulmonary disease (COPD). Also known as emphysema or chronic bronchitis, COPD is a major cause of disability and death. It has no cure and is characterized by shortness of breath, chronic coughing, wheezing, frequent respiratory infections, fatigue, and producing a lot of phlegm, according to the American Lung Association.
Smoking is the main cause of COPD and quitting smoking remains the number one recommendation for reducing COPD risk. But a surprising new study in the Annals of the American Thoracic Society suggests that the amount of dietary fiber you consume may also have an affect on lung function.
Researchers at the University of Nebraska Medical Center analyzed data from the National Health and Nutrition Examination Surveys (NHNES). This research on 1,921 adults conducted by the Centers for Disease Control included a physical examination, which measured lung function. Investigators found that 68% of the participants who consumed the most fiber—at least 17.5 grams a day—had normal lung function, compared with just over 50% of those who consumed less than 10.75 grams of fiber a day. On the flip side, only 14.8% of those with high dietary intake had airway restriction, compared with close to 30% of those with low fiber intake.
How Does Fiber Protect the Lungs?
The researchers can’t say how fiber—known mostly for its ability to help people feel full and lower "bad" cholesterol—protects the lungs, but one theory has to do with the metabolism (the way food is used for energy) of fiber by the so-called "good" bacteria in the gut.
"These bacteria are able to metabolize fiber and use it for their food, so the more fiber you eat, the more good bacteria you have," explains Corrine Hanson, Ph.D., RD, University of Nebraska Medical Center, Omaha, and lead author of the study.
It’s the by-products of this metabolism, called short-chain fatty acids (SCFA), which researchers are looking at: "These SCFA appear to have pretty strong anti-inflammatory effects, and we do know that they leave the GI [gastrointestinal] tract and get into systemic circulation, where they may be able to impact other organs. Since COPD is an inflammatory disease, these anti-inflammatory compounds may help the lungs."
In future studies, Hanson and her team hope to measure the actual SCFA production in people who eat different amounts of fiber, and compare that to levels of inflammatory biomarkers in the blood.
In the meantime, it wouldn’t hurt to help yourself to more servings of fiber, even if you don’t have COPD. "Our study showed that fiber improved lung function in the general, healthy population, as well as in people with COPD," adds Hanson. "At this point we would recommend at least 17 grams [of fiber a day]. We don’t know if more is better for lung disease, but in our study, 17 was better than less than 17."
Five Ways to Add More Fiber to Your Diet
Are you eating enough fiber to reap the benefits? Possibly not: Americans consume about 16 grams a day, but the recommended amount is 21-38 grams a day, according to the National Institutes of Health. Here are five ways to add more fiber to your diet:
- Start the day with oatmeal or high-fiber cereal. Look for a variety that contains at least 5 grams of fiber per serving.
- Eat fruits, such as apples and pears, with the peels intact. Much of their fiber content is in the peel.
- At lunch, include beans. Toss garbanzo beans (chick peas) in your salad. Or opt for lentil or black bean soup as a side. Speaking of sides, aim to include at least one serving of vegetables at every meal.
- Go nuts. Afternoon munchies? Skip the vending machine and snack on a handful of peanuts, cashews, or walnuts.
- Swap refined "white" carbs for whole-grain varieties. At dinner, choose brown rice instead of white, and try whole-grain pasta and breads.
Corrine Hanson, PhD, RD, reviewed this article.
Sources
Corrine Hanson, PhD, RD. Email correspondence with author. April 2, 2016.
Hanson C, Lyden E, Rennard S, Mannino D M, Rutten E P A, Hopkins R, Young R. "The Relationship between Dietary Fiber Intake and Lung Function in NHANES." Annals ATS. First published online 19 Jan 2016 as DOI: 10.1513/AnnalsATS.201509-609OC.
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