Dietary Fiber May Improve Lung Health

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One recent study suggests that eating high fiber diet can promote better Lung functionality where as people who consume low fiber food are more likely to suffer from disorders of lung including Asthama and COPD.

A study of data from National Health and Nutrition Examination Surveys (NHANES) found that high fiber diet reduced airway constrictions in lungs for those who take more fruits and vegetables.  This was found in a study done in the University of Nebraska Medical Center in Omaha as reported by Corine Hanson.

They found that this study was also true for people who smoked and were over weight.  This report was published in the Annals of the American Thoracic Society.

Fruit and vegetable consumption was more strongly associated with higher lung function than consumption of whole grains in the analysis, and this association was independent of antioxidant intake, which has previously been shown to be positively associated with lung function.

“These findings are pretty consistent with several other [observational] studies examining fiber and lung function. The difference in the studies has been in the types of fiber that appear to be protective,” Hanson told MedPage Today in a telephone interview. “We found an association with fruits and vegetables, but not cereal grains. Other studies suggest that cereal grains may be more important.”

The researchers wrote that there is extensive research linking high fiber intake with a lower risk for heart disease and certain cancers, but less evidence linking fiber intake to lung health.

“Dietary fiber has been shown to exhibit both anti-inflammatory and anti-oxidant properties, which have been implicated in both the development and progression of lung disease,” they wrote.

To test their hypothesis that lower fiber intake is associated with reduced lung function, the researchers examined data on adults surveyed for in NHANES cycle 2009-2010.

The analysis included 1,921 adults, ages 40 to 79, with available pre-bronchodilator spirometry measurements. The Global Initiative for COPD (GOLD) classification was used to establish the presence and severity of airflow obstruction based on spirometry measures. Dietary intake was determined from two interviewer-administered, 24-hour recalls, developed by the U.S. Department of Agriculture.

All participants were asked about their smoking history, and smoking status was defined as: never, former (>100 cigarettes in a lifetime, not current), and current (>100 cigarettes, smoking currently).

The primary outcomes were lung function measurements, including FEV1, FVC, and percent predicted FEV1 and FVC. The researchers also conducted a categorical analysis of fiber intake and airflow restriction and obstruction based on GOLD and Spirometry Grade (SG) classifications.

Multivariable regression models were used to examine the association of lung function measurements with dietary fiber intake after adjustment for relevant confounders. All analyses accounted for the weighted data and complex design of the NHANES sample.

The analysis revealed that surveyed participants in the highest quartile intake of fiber had mean FEV1 and FVC measurements that were 82 mL and 129 mL higher that the lowest quartile of intake (P=0.05 and 0.01, respectively), and mean percent predicted FEV1 and FVC values that were 2.4 and 2.8 percentage points higher (P=0.07 and 0.02, respectively).

Also, in the categorical analysis, higher fiber intake was associated with a higher percentage of participants with normal lung function (P=0.001) and a significant decline in the proportion of participants with airflow restriction (P=0.001).

With increasing daily fiber intake, the percentage of those with normal lung function increased — 50.1% versus 68.3% for quartile 1 (Q1) versus Q4 (P=0.001) — although the effect was attenuated at quartiles 3 and 4. For increasing daily fiber intake, there was a significant decline in the proportion of participants with airflow restriction (29.8% versus 14.8% for Q1 versus Q4, P=0.001) which again was attenuated at the higher quartiles.

The authors also reported that participants with a higher fiber intake tended to have a lower BMI, and a higher intake of fruits, vegetables, and whole grains.

“Intake of fruits, vegetables and legumes were associated with lung function in our study independent of intake of antioxidants previously associated with lung function,” they pointed out. “Several studies have found stronger associations with intakes of whole fruitwhen compared to individual fruit-related nutrients.”

The association between high dietary intake and lung function was independent of antioxidant intake, intake of cured meat and other possible dietary risk factors, the authors noted.

The cross-sectional nature of the NHANES data was a study limitation, precluding the establishment of a causal relationship between higher fiber intake and better lung function.

“It could be proposed that fiber is a surrogate measure for overall healthy lifestyle,” they wrote.

A study strength was the use of spirometry measurement to identify airflow limitations, “as opposed to the self-reported diagnosis of COPD used in many epidemiological studies,” the researchers wrote.

Hanson told MedPage Today that the consistent finding in the observational data of a possible protective benefit for high-fiber intake in lung function could have important public health implications for the public at large and very high-risk groups, such as smokers.

“There are very few interventional strategies for the prevention of COPD, with the exception of not smoking or smoking cessation,” she said. “This is a non-invasive, very inexpensive strategy that may be good for your lungs.”

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