JUN 22, 2016

More Fiber, Reduced Allergy Severity - At Least for Mice

WRITTEN BY: Kara Marker

Findings from a new research study might convince you to feed your gut microbiota a little better. The population of “good bacteria” that lives in the human gastrointestinal tract has a huge impact on human health, providing benefits for the immune system and for digestion. The current study focuses on food allergies, fiber, and finding the right diet to reduce the increasing incidence of food allergies in the current society.

The bacteria in the gut microbiome eat what you eat, and a new study suggests that the development of food allergies in mice depends on what their gut bacteria are "eating.” In effort to explain why cases of food allergies seem to be on the rise, especially within the last ten years, scientists often look at high-fat diets as an answer. The current study is the first to look to fiber deficiencies, using mice with artificially-induced peanut allergies to make a new claim.

First, they fed the allergy-induced mice a high-fiber diet to cultivate a population of healthy gut bacteria. Then, the healthy microbiota was transferred into mice without any gut microbiota at all. Thanks to the bacterial transplant, the second group of mice were successfully protected from peanut allergic responses without having to include any fiber in their diet at all: they responded much less seriously after being exposed to peanuts than they did without the healthy microbiota injection.

Co-senior author Charles Mackay, PhD calls a healthy microbiome an “essential component of their nutritional health,” and the same is thought to be true for humans by most scientists.

Gut bacteria have a special relationship with fiber: they release short-chain fatty acids in response to fiber in the diet. These fatty acids then make changes in the immune system that scientists believe are responsible for controlling allergic responses. These changes are more than likely related to lymphocytes called T regulatory cells (T regs) and their receptors. T regs maintain equilibrium in the immune response so it doesn’t overreact, and most cases of autoimmune disease have something to do with T reg dysfunction.

As compared to a high-fiber diet, a diet of average calories, sugar, and fiber from birth is more likely to result in more severe peanut allergies. Co-senior author of the study Laurence Macia, PhD, believes the gut microbiota are supporting the development of T regs and that promoting T regs ensures the bacteria have a healthy place to live. "It's a win-win for everybody," Macia said.

Additional experiments manually inserting short-chain fatty acids in the gut produced the same results as when the scientists created a healthy microbiome and challenged mice with peanuts. These mice had reduced allergic responses after exposure to peanuts even without a population of gut bacteria that were fiber-primed to produce their own short-chain fatty acids.

The researchers are continuing to support fiber as capable of reducing severity of food allergies with "cautious optimism.” They still aren’t sure what source of fiber is best for achieving the goal and if the relationship between fiber and the gut microbiota in humans will be the same as the studies in mice.

Either way, researchers are convinced that it's not that 21st century humans are eating too much fat, it's that they are not eating enough fiber, as compared to ancient ancestors who didn't seem to have as much of a problem with food allergies and other auto-inflammatory conditions.

This study was recently published in Cell Reports.

Sources: Cell Press, Scandinavian Journal of Immunology