Influenza is one of the most common – and, in some instances – one of the most deadly illnesses on the planet. But a new study indicates that a diet high in a type of fiber known as inulin could help provide protection.
The results of the study appeared in the May 15, 2018, issue of the medical journal Immunity.
Now, to be clear — this information is brand new — and further tests (including human tests) are still needed before treating fiber as a “flu fix.” So if you’re suffering from the flu, or concerned about the flu, speak to your doctor.
Conventional scientific wisdom holds that high-fiber diets could actually hamper the ability of the immune system to fight off the influenza virus, which typically affects up to 20 percent of the world’s population each year. This new study, however, may change that way of thinking.
Researchers used two groups of mice for the study. They gave one group a diet high in inulin (a type of fiber found in onions, garlic, and the rinds of citrus fruits). The other group of mice ate mainly cellulose. They then exposed the mice to the influenza A virus.
According to the results, the mice receiving a high-fiber diet acted normally compared to the cellulose group. They appeared to be better protected from the flu. The researchers then gave two different sets of mice (one eating a high-fiber diet, the other cellulose) a higher dose of the virus. While the inulin-fed mice became ill, they survived. The other group did not.
Why did the mice eating the high-fiber diet survive?
Researchers theorize that the dietary fiber helped to activate T-cells in the mice.
And these T cells then specifically targeted, and successfully fought off, the influenza virus. At the same time, the diet helped to suppress an excessive immune response that could have damaged lung tissue.
In addition, the high-fiber diet stimulated the production of short-chain fatty acids (SCFA) by bacteria in the gastrointestinal tract. Researchers had previously thought that SCFAs could reduce the effectiveness of the immune system. But the study results seem to indicate the opposite.
“The beneficial effects of dietary fiber and SCFAs on a variety of chronic inflammatory diseases, including asthma and allergies, have received substantial attention in recent years and have supported momentum toward their use in clinical studies,” said Benjamin Marsland, the lead researcher on the study. “But we were concerned that these treatments might lead to a general dampening of immune responses and could increase susceptibility to infections.”
“What surprised us was that dietary fiber was selectively turning off part of our immune system, while turning on another, completely unrelated part of our immune system,” Marsland added.
The findings suggest that diets that are low in fiber could not only result in a higher susceptibility to infectious, but also inflammatory diseases. However, these studies were only done on rodents. Scientists say more research will be needed before it can be determined exactly what type of fiber could help protect humans from viruses.
“There is a need for carefully designed and controlled dietary or SCFA intervention studies in humans to address how these findings could be exploited to benefit people with asthma, or for preventing viral infections,” Marsland said. “We should also look further into these pathways as a means of supplementing other therapies or enhancing vaccine efficacy.”