High Dietary Fiber Lowers Systemic Inflammation: Potential Utility in COPD and Lung Cancer

In their cross-sectional National Health and Nutrition Examination Survey study, Grooms et al found that a high fiber intake was associated with a reduction in systemic inflammation, obesity, and metabolic syndrome, even after adjustment for important confounding variables. This beneficial effect was strongest for systemic inflammation, which affected 35% of the population. We describe why a diet high in fiber also might confer benefits in smoking-related lung disease and suggest that respiratory outcomes be correlated with fiber in the National Health and Nutrition Examination Survey cohort.

Prospective studies show that between 50% and 70% of those developing chronic obstructive pulmonary disease and lung cancer have elevated systemic inflammation (compared with 53% in cardiovascular disease).^,  Recently, we suggested that systemic inflammation, initiated by smoking in genetically susceptible people, is a primary determinant of both chronic obstructive pulmonary disease and lung cancer, linking these diseases through overlapping pathogenetic pathways. Such a hypothesis might explain why systemic inflammation is associated consistently with poor outcomes in chronic obstructive pulmonary disease (including lung cancer). It also might explain the large body of evidence showing that inhibition of systemic inflammation, through the use of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins), is associated consistently with reduced mortality in chronic obstructive pulmonary disease and lung cancer. Recently, we proposed that a high intake of legumes (high in fiber) might confer beneficial effects in ex/smokers through their anti-inflammatory effect. Indeed, diets high in fiber have been shown to significantly reduce systemic inflammation and disposition to chronic obstructive pulmonary disease. We believe this might be through the absorption of colonic small chain fatty acids known to have anti-inflammatory effects (inhibits 3-hydroxy-3-methylglutaryl-coenzyme A reductase) and anti-neoplastic effects. If this were true, then the high-fiber intake of Mexicans described by Grooms et al and Young and Hopkins, might partly explain their lower rates of chronic obstructive pulmonary disease and lung cancer (basis of Hispanic paradox).

Although we agree with Grooms et al that optimizing dietary fiber intake might help reduce poor outcomes in cardiovascular disease, we believe these benefits might extend to smoking-related lung disease, in which systemic inflammation is more prevalent and consistently linked to poor outcomes. Although the role of statins in reducing systemic inflammation has established chemopreventive utility, a diet high in dietary fiber seems worthy of investigation.