Dietary Fibre

Australian scientists have found a “direct link” between what we eat and how well our immune system operates, a breakthrough that could explain rising rates of autoimmune disease across the western world.

According to this research insoluble dietary fibre, or roughage, not only keeps you regular, it also plays a vital role in the immune system, keeping certain diseases at bay. Dietary fibre, the indigestible part of all plant-based foods, pushes its way through most of the digestive tract unchanged, acting as a kind of internal broom. When it arrives in the colon, bacteria convert it to energy and compounds known as ‘short chain fatty acids’. These are already known to alleviate the symptoms of colitis, an inflammatory gut condition.

Professor Charles Mackay, working at Sydney’s Garvan Institute of Medical Research, identified how fibre in the diet also plays a vital role in the immune system, keeping certain diseases at bay.

His research, published in the prestigious scientific journal Nature (Oct 2009), also signals the shift of what had been a fringe concept into the scientific mainstream.

“This potentially explains all the previous data that no one had taken that seriously,” Prof Mackay said. “I think it’s fair to say the broader immunological research community has never really believed that diet affects immune responses.

“This does provide a direct link for the way immune cells work with the sort of things we eat.”

Working along with PhD student Kendle Maslowski, Prof Mackay investigated the operation of an immune cell receptor known to bind with “short chain fatty acids” – what fibre is reduced to once processed by bacteria in the gut.

This broken-down fibre was found to “profoundly affect immune cell function”, Prof Mackay said, and without it the immune cells appeared more likely to go awry. Autoimmune disease refers to disorders in which a person’s immune system mistakenly attacks part of the body, causing inflammation.

“When (immune cells) go bad they cause inflammatory diseases, so asthma, rheumatoid arthritis, inflammatory bowel disease…” Prof Mackay said. “We think one of the mechanisms for their normal control is short chain fatty acids binding to this receptor. “And if we were to speculate on the real significance of this, we believe firmly that the best explanation for the increase in inflammatory diseases in western countries… is our changes in diet.”

A lack of dietary fibre could also be behind the rise in type 1 diabetes, Prof Mackay said. The conclusions drawn from the current research provide some of the most compelling reasons yet for eating considerably more unprocessed whole foods – fruits, vegetables, grains, nuts and seeds.

It also helped to explain why food supplements that affect the balance of gut bacteria were known to reduce the symptoms of some inflammatory conditions. Prof Mackay said dietary fibre, or roughage, was otherwise known to reduce the risk of cardiovascular disease and certain cancers plus it ensures you will be regular. “The role of nutrition… is an exciting new topic in immunology,” he said.

New findings connect diet and intestinal bacteria with healthier immune systems
Professor Charles Mackay, Garvan Institute of Medical Research