A high-fiber diet reduces the severity of allergic airway disease, including decreased lung inflammation, in mice according to a study published online in Nature Medicine. These findings highlight how diet can influence immune cell development and disease outside of the gut.
Over recent decades, the incidence of allergic asthma has increased in developing countries, while the consumption of dietary fiber has decreased in these countries. Although dietary fiber intake can improve gastrointestinal disorders, it remains unclear whether it influences inflammation outside of the gut.
Benjamin Marsland and his colleagues report that mice fed a low-fiber diet develop worse lung inflammation in response to allergen challenge whereas those fed a high-fiber diet enriched with pectin have reduced allergic airway disease. The authors find that dietary fiber alters the composition of bacteria in the gut. Once ingested, these bacteria process the fiber and release metabolites, called short-chain fatty acids, which enter the blood circulation and influence the development of immune cells elsewhere in the body, including those entering the lung. In mice, administration of propionate, a short-chain fatty acid produced when gut bacteria metabolizes fiber, without increasing dietary fiber also reduced allergic inflammation in the lung and elicited the same protective effect as the pectin-rich diet.