**5. Short-chain fatty acids (SCFAs) are produced by fermentation of fiber**

Through the fermentation of food fibers to SCFA, the gut microbiota may influence immune cells. Increased natural killer cell activity is an outcome of SCFA. SCFA has also been presented to have anti-inflammatory properties in other investigations. In the colonic cell line HT-29, butyrate was found to decrease both constitutive and cytokine-induced production of the transcription factor NFkB [13].

Finally, SCFA generation in the colon, particularly butyrate, may lessen the glutamine need of epithelial cells, freeing it up for other cells such as immune system cells. The fact that lactulose injection can raise serum glutamine levels, and glutamine is a vital energy source for immune cells, which supports this notion [16].

The addition of fermentable fibers to the diet has been shown to boost mucin synthesis. The reduced incidence of bacterial translocation across the intestinal barrier observed in studies feeding dietary fibers could be due to increased mucin synthesis. The increased mucin formation may be due to the lower pH associated with SCFA production.
