New research on the impact fiber has on GI health and immune function has experts encouraging more fruits and vegetables in our diet.
Old research has shown high fiber diets are linked to lower risk of heart disease, diabetes, and hypertension as well as lower mortality rates from all causes. We have known for a while that fiber is great for us, but we are still learning exactly how it generates benefits.
One new study surveying the effects of switching from a high-fiber diet to a low-fiber diet high in protein, fat, and sugar in mice shows the impact of fiber on immune function. Within a few days of the diet change intestines got smaller and the mucus layer covering the intestinal walls was thinner resulting in closer bacterial contact. This led to an immune reaction and inflammation. Mice experienced higher blood sugar levels and began gaining weight. A second group of mice were fed the same diet but also given a fiber supplement resulting in healthy bacteria populations in their GI tract, normal appearing intestines, and less weight gain.
Scientists speculate low-fiber diets starve healthy bacteria in the GI tract, intestinal cells slow their mucus production, and as bacteria moves closer to the intestine's the immune system is impacted. Furthermore, scientists speculate immune response and inflammation occurs throughout the entire body and not just in the GI tract, which could play a role in heart disease, diabetes, and cancer risk.
It has also been speculated different types of fiber from different plants might play a role in how healthy bacteria in the gut functions.
Studies in humans need to be carried out to better understand the impact of fiber on our immune function, but this promising research is only the beginning of linking our GI tract to our overall health.