Sydney: 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.

Professor Charles Mackay, of Sydney’s Garvan Institute of Medical Research, has identified how fibre in the diet plays a major role in ensuring a person’s immune cells function properly.

His results published in the prestigious journal Nature, also reaffirm the shift of what was once had 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” – the end product of fibre after being processed by gut bacteria.

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, asthma, rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis …” 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 research suggests that having a healthy diet rich in fruits, vegetables, grains, nuts and seeds would reduce a person’s risk of autoimmune disease.

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.

Commenting on the study, Helen Yates, of the Multiple Sclerosis Resource Centre Chief Executive said, “This is a very important finding in the field of diet and immune systems. It has long been believed by many people in the MS community that diet has a role to play in the disease and this research represents a first step towards greater investigation of how the food we eat can influence the immune system diseases we develop”