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Fiber-Rich Diet May Boost Lung Function

Authors note an association with intake of fruits and veggies

by Salynn Boyles
Contributing Writer

Action Points

Low dietary fiber intake was associated with reduced lung function, suggesting that eating a diet rich in fiber may protect against lung diseases like chronic obstructive pulmonary disease and asthma.
Note that 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.

Low dietary fiber intake was associated with reduced lung function, suggesting that eating a diet rich in fiber may protect against lung diseases like chronic obstructive pulmonary disease (COPD) and even asthma, researchers said.

In an analysis of National Health and Nutrition Examination Surveys (NHANES) data, adults with the highest fiber consumption were more likely to have normal lung function and they were less likely to have airway restrictions compared with adults whose diets contained the least fiber, reported Corrine Hanson, PhD, RD, of the University of Nebraska Medical Center in Omaha, and colleagues.

These associations were found to be consistent, even when controlling for important covariates for poor lung function, including smoking and high body mass index (BMI), they wrote 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. In addition to information on dietary intake, the survey included spirometry measures.

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 fruit when 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."

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

last updated 01.27.2016

Primary Source
Annals of the American Thoracic Society
Source Reference: Hanson C, et al "The relationship between dietary fiber intake and lung function in NHANES" Ann Am Thorac Soc 2016; DOI: 10.1513/AnnalsATS.201509-609OC.

http://www.medpagetoday.com/Pulmonology/SmokingCOPD/55857?xid=nl_mpt_DHE_2016-01-27&eun=g379602d0r

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Heather is the Administrator of the IBS Message Boards. She is the author of Eating for IBS and The First Year: IBS, and the CEO of Heather's Tummy Care. Join her IBS Newsletter. Meet Heather on Facebook!

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Fecal Profiling May Predict Dietary Response in IBS
Baseline VOCs correlate with symptom relief in patients on low-FODMAP diet

by Diana Swift, Contributing Writer
March 15, 2018

Fecal profiling of volatile organic compounds may provide a low cost, non-invasive tool to predict the responses of irritable bowel syndrome (IBS) patients to probiotics and diets low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs).

Note that this approach can potentially shed light on the pathophysiology of IBS, and has the potential to advance its clinical management with more precisely personalized nutrition regimens.

Fecal profiling of volatile organic compounds (VOCs) may provide a low cost, non-invasive tool to predict the responses of irritable bowel syndrome (IBS) patients to probiotics and diets low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), according to British researchers.

Modeling baseline fecal VOCs, and using key features of VOC profiles, correctly predicted response to a low-FODMAP diet in 100% of patients and in 89% of patients receiving a probiotic, reported Megan Rossi, PhD, RD of King's College in London, and colleagues.

This approach can potentially shed light on the pathophysiology of IBS, and advance its clinical management with more precisely personalized nutrition regimens, they wrote in Clinical Gastroenterology and Hepatology.

Multiple randomized trials have indicated that the low-FODMAP diet is effective in 50%-80% of IBS patients. "However, predicting response is clinically important because the diet requires intensive dietary counselling and impacts on both the gut microbiota and nutrient intake, and, therefore, avoiding this intervention in the 20%-50% who are unlikely to respond would be an important clinical advance," Rossi's group noted.

New approaches are definitely needed, according to William D. Chey, MD, of the University of Michigan in Ann Arbor.

"Only about half [of patients] get better on the diet, which has associated shopping costs and inconvenience to the patient, plus input from a dietitian and an extended three-step period of time to work through its stages," Chey told MedPage Today. "This often gets glossed over but it's not a trivial thing."

Chey, who was not involved in the study, further explained that little is known about the long-term nutritional and microbiotic downsides of this restrictive diet. "By excluding prebiotic carbohydrates, you are very likely to have effects on the microbiome, so it's important to identify strategies that enrich the likelihood of response and maximize choosing the right treatment for the right patient," he said.

Rossi's group used data and samples from patients with IBS-diarrhea, IBS-mixed, and IBS-unsubtyped treated at two major London hospitals and participating in a previous clinical trial. A total of 95 patients (majority white), whose age ranged from early to late 30s, completed the study. Of these, 93 (63 women) provided sufficient fecal sample for analysis and were randomized for 4 weeks to a low-FODMAP diet (n=46) or a sham diet plus dietary advice (n=47).

In 2-by-2 factorial fashion, patients in both dietary groups also received either a multi-strain probiotic supplement (n=49) or a placebo supplement (n=44).

Gas chromatography assessed VOCs in fecal samples at baseline and at study completion. The clinical endpoint was the IBS Severity Scoring System (IBS-SSS), which records abdominal pain, distension, stool frequency and consistency, and interference with life over a 10-day period.

All 93 participants were deemed compliant with diet, and 86 were classified as compliant with supplementation. At the end of the study, those in the low-FODMAP arm had a significantly lower total FODMAP intake (20+8 g/day) compared with those on the sham diet (33+16 g/day, P<0.001).

In terms of response, more patients reacted clinically to the low-FODMAP diet (37/46, 80%) than the sham diet (21/47 45%, P<0 .001), with a mean change in IBS-SSS score of �130 and �49 (P<0.001), respectively.

There was no difference in clinical response between patients given the probiotic (31/49, 63%) versus placebo (27/44, 61%, P=0.850), with no synergistic or antagonistic effects observed with supplementation. In addition, there was no difference in the mean change in IBS-SSS score between recipients of probiotic (�88) and placebo (�90, P=0.921).

The researchers found that baseline VOC profiles contained 15 features that explained 25% of response variation to the low-FODMAP diet with a mean accuracy of 97% (95% CI 96%-99%), as well as 10 features that explained 30% of response variation to the probiotic, with a mean accuracy of 89% (95% CI 86%-92%). At end of treatment, nine observed compounds explained 31% of variation in response to low-FODMAP and 11 compounds explained 27% of variation with the probiotic.

As to how VOCs predict response, the authors pointed out that many of these compounds are created from indigestible food substrates in the colon through both microbial metabolic activity and diet. VOC patterns at baseline may reflect the pathophysiology of an individual's IBS and eating a high-FODMAP standard diet may, in the presence of IBS-associated dysbiosis, generate fermentation products that cause symptoms. Once the normal diet has been replaced, there is less substrate for bacterial metabolism and gas production and associated symptoms are reduced.

Study limitations included the relatively small sample size, its exploratory nature and the lack of data to inform a power calculation. Also, since the device that assessed fecal VOCs identified patterns of VOCs, not individual VOCs, detailed investigation of the potential mechanisms of individual VOCs could not be done. Finally, the 2-by-2 factorial design may have clouded the results.

Chey noted that, in his experience, about half of patients improve on the low-FODMAP diet, a remarkably high rate of success for a dietary therapy. Also, some of his patients have been following a reduced-FODMAP diet since his institution began introduced it in 2008.

"And up to 85% can move to a less restrictive diet after the phase of determining sensitivities," Chey said.

This study was funded by the National Institute of Health Research.

Rossi and Chey disclosed no relevant relationships with industry. Two co-authors disclosed being co-inventors of a mobile application for the low-FODMAP diet.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

last updated 03.15.2018

Primary Source
Clinical Gastroenterology and Hepatology
Source Reference: Rossi M, et al "Volatile Organic Compounds in Feces Associate With Response to Dietary Intervention in Patients With Irritable Bowel Syndrome" Clin Gastroenterol Hepatol 2018; DOI:10.1016/j.cgh.2017.09.055.

https://www.medpagetoday.com/gastroenterology/irritablebowelsyndrome/71777

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Heather is the Administrator of the IBS Message Boards. She is the author of Eating for IBS and The First Year: IBS, and the CEO of Heather's Tummy Care. Join her IBS Newsletter. Meet Heather on Facebook!

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