DIETARY FIBER IMPACT ON INFECTION
Eating more fiber is one way to boost your immune system and fight infections.
- Dietary fiber has a significant protective effect on infections of the lungs
- Increasing fiber intake is a simple way of increasing protective immunity and reducing the severity of an infection
- Increasing dietary fiber consumption by 5g per day (roughly a handful of berries or nuts) is an easy way to add this life-saving nutrient
A bit more detail
Fiber, through its central influence on our gut microbiota, is known to have a positive effect on inflammation in general, and diseases of the airways that involve an immune response from the body in particular.
Among many other benefits of fiber, it is metabolized by some of our gut bacteria into short chain fatty acids. These have a profound effect on our immune system in terms of reducing inflammation and a wide range of other benefits. A number of studies also show that the positive effects relate to the development of protective immunity and reduced immune system-linked tissue damage when lungs are infected with flu.
While all deliberate infection studies have been done on animals, one study with over 400 students showed a 40% reduction in the percentage of days with cold or flu in normal-weight individuals with 5.0g of additional fiber consumption per day.
 In particular, acetate, propionate, and butyrate
 Corrêa-Oliveira R, et al.; .Regulation of immune cell function by short-chain fatty acids. Clin Transl Immunology. 2016;5(4):e73.
Ríos-Covián, David et al. “Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health.” Frontiers in microbiology vol. 7 185
 Trompette, A et al.; Dietary Fiber Confers Protection against Flu by Shaping Ly6c− Patrolling Monocyte Hematopoiesis and CD8+ T Cell Metabolism.; Immunity, Volume 48, ISSUE 5, P992-1005.e8, May 15, 2018
Tirawattanawanich, C., The Modulating Effects of Dietary Fiber and Short-Chain Fatty Acids on Enterocyte Differentiation, Maturation, and Turkey Coronavirus Infection. Dissertation submitted to the Faculty of Virginia Polytechnic Institute & State University, 2001
Christine Hughes et al., Galactooligosaccharide supplementation reduces stress-induced gastrointestinal dysfunction and days of cold or flu: a randomized, double-blind, controlled trial in healthy university students
The American Journal of Clinical Nutrition, Volume 93, Issue 6, June 2011, Pages 1305–1311
The broad effect extends to other diseases of the lungs such as COPD: Kan, Haidong et al. “Dietary fiber, lung function, and chronic obstructive pulmonary disease in the atherosclerosis risk in communities study.” American journal of epidemiology vol. 167,5 (2008)