The connection between fibre and gut health has long been established. However, one study believes that a high-fibre diet can also combat the flu.
A fibre-rich diet is widely recognised for reducing inflammation in the gut, and therefore aiding intestinal health. But recent findings from Monash University – which were published in Immunity – have also found that fermented fibre and short-chain fatty acids (SCFAs) – the by-products of the fermentation process – may actually hold protective properties against viral infections including the flu, as well as having potential to improve the efficacy of flu vaccines.
Professor Benjamin Marsland from the Department of Immunology, along with scientists from the University Hospital of Lausanne in Switzerland, discovered that in mice, fibre fermented in the gut by bacteria may contain properties to combat one of the world’s most common viral diseases – influenza A.
Professor Marsland said, “What is produced in the gut doesn’t just change what’s in the gut. It goes into the circulation and changes the immune system at one of the most fundamental levels – the bone marrow – where a lot of our immune cells develop.”
Dietary fibre is known to potentially decrease immune responses by turning the immune system off, but instead of this occurring, the diet was found to actually activate the “cytotoxic T cells”, which are those responsible for killing virus-infected cells.
“This was about turning a discrete part of the immune system on, which is very novel,” explained Professor Marsland. “In essence, by eating the high-fibre diet, the immune system of the mice had been primed to fight against infections. We were very excited by that.”
These findings could potentially be used to enhance the effectiveness of flu vaccines, by adding SCFAs to vaccines or by supplementing the diet with the appropriate fermentable fibres.
The discovery came as a surprise because, as Professor Marsland explained, “the expectation from our earlier work, and that of others, would be that the immune response would be dampened.” This “earlier work” refers to a previous discovery by Professor Marsland and his team, that mice were protected against asthma when fed a diet high in fermentable fibre. The research team had hoped to examine the impact of a high-fibre diet on the influenza virus in mice, but feared that the “dampening down” of the immune system, which was observed in the asthma study, may further suppress the mice’s immune system, leaving them at risk of developing other diseases or infections.
These latest findings could now potentially be used to try to enhance the effectiveness of flu vaccines, by adding SCFAs to vaccines or by supplementing the diet with the appropriate fermentable fibres. And of course, as suggested by Professor Marsland, there may also be potential application to other viruses.
SCFAs are often found in sources including root vegetables such as chicory roots or the skins of citrus fruits, but at this stage of the research, it is still unknown exactly which fibre or how much should be taken, in order for it to be effective.
Clinical research is planned, to determine whether people who eat different amounts of inulin (a soluble plant fibre cited in the paper) are protected against lung disease. Professor Marsland explained that inulin, which is increasingly entering the spotlight for its link with “healthy bacteria”, is readily available, tolerable and safe.