Insoluble dietary fiber, or roughage, not only keeps you regular but also plays a vital role in the immune system, keeping certain diseases at bay, say Australian scientists.
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.
Similarly, probiotics, and prebiotics, food supplements that affect the balance of gut bacteria, reduce the symptoms of asthma and rheumatoid arthritis, also inflammatory diseases. Until now, no one has understood why.
Doctoral student Kendle Maslowski and professor Charles Mackay from the Garvan Institute of Medical Research made new sense of such known facts by describing a mechanism that links diet, gut bacteria and the immune system. They demonstrated that GPR43, a molecule expressed by immune cells and previously shown to bind short chain fatty acids, functions as an anti-inflammatory receptor,
“The notion that diet might have profound effects on immune responses or inflammatory diseases has never been taken that seriously” Mackay said. “We believe that changes in diet, associated with western lifestyles, contribute to the increasing incidences of asthma, Type 1 diabetes and other autoimmune diseases. Now we have a new molecular mechanism that might explain how diet is affecting our immune systems.”
Maslowski said, “We’re also now beginning to understand that from the moment you’re born, it’s incredibly important to be colonized by the right kinds of gut bacteria. The kinds of foods you eat directly determine the levels of certain bacteria in your gut.”
“Changing diets are changing the kinds of gut bacteria we have, as well as their by-products, particularly short chain fatty acids. If we have low amounts of dietary fiber, then we’re going to have low levels of short chain fatty acids, which we have demonstrated are very important in the immune systems of mice.”
Mice that lack the GPR43 gene have increased inflammation, and poor ability to resolve inflammation, because their immune cells can’t bind to short chain fatty acids.
Conclusions from the most recent research provide some of the most compelling reasons yet for eating considerably more unprocessed whole foods: fruits, vegetables, grains, nuts, and seeds.
