Soluble Fiber, Not Vitamin C, Protects Mice Against The Flu Virus

Many people drink orange juice for vitamin C when they feel a cold or flu coming on, but if work on rodents proves transferable, they might get more benefit from eating the rind. The discovery is something of a amaze because previous run led scientists to think that high-fiber diets might actually decrease immunity. Instead, something more complex and intriguing happened.

Dietary fiber might seem unrelated to the immune system, but previous research has indicated a connection. It is thought this results through the production of short-chain fatty acids( SCFAs) by intestine bacteria in response to soluble fiber in the diet.

“The beneficial effects of dietary fiber and SCFAs on a range of chronic inflammatory diseases, including asthma and allergies, have received substantial attention in recent years, ” said Professor Benjamin Marsland of Monash University in a statement. “But we were concerned that these treatments might lead to a general dampening of immune the replies and could increase susceptibility to infections.”

Marsland exposed two groups of mice, one on a diet high in the soluble dietary fiber inulin, and the other fed insoluble cellulose, to the influenza A virus. Far from the inulin-eaters getting sicker, as might be expected if the SCFAs repressed their immune systems, they actually appeared healthier. He told IFLScience; “The control mice huddled together, their fur ruffled, they looked like they had the flu. The mice on the high inulin diet ran around the cage and seemed healthy.” Blood and lung exams confirmed appearances.

Surprised, Marsland and my honourable colleagues operated the experiment again with new mice, and a ordinarily lethal dosage of the flu virus. The high-inulin mice got sick but survived.

“Dietary fiber was selectively turning off part of our immune system, while turning on another, altogether unrelated part of our immune system, ” Marsland concluded. The aspects of the immune system that cause inflammation were being dialed down, reducing damage to lung cells, just as pass for allergies and asthma in the presence of SCFAs. On the other hand, Marsland reported in Immunity, the T-cells that kill cells infected by pathogens became far more active, providing a powerful viral defense.

A comparison of the response to a low-fiber diet, and one rich in soluble fiber in the context of influenza infection. Trompette et al/ Immunity

Marsland stressed to IFLScience it is important to be careful extrapolating from rodent research, but said we know human gut bacteria also render SCFAs when we increase our soluble fiber intake. What Marsland hopes to test is how much extra fiber we need to gain a meaningful benefit, and which kinds of soluble fiber work best.

Inulin is already added to some processed foods and is found in garlic, onions, and Jerusalem artichokes. The peel of citrus fruits is a particularly rich source, so break out the marmalade.

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