NUTRITION
November 13, 2009

Fiber Fights Inflammation

Scientists have recently discovered why fiber is so good for the immune system. The answer lies in the by-products of the breakdown of fiber.

It has been known for some time that adding fiber to the diet or tweaking the number of bacteria in the gut can help with the inflammatory diseases colitis, rheumatoid arthritis, and asthma, but until recently researchers weren’t quite sure why. Now the results of a new study suggest that short−chain fatty acids – an end−product of the break−down of fiber – may be at work, by activating a receptor that acts as an anti−inflammatory agent.

Charles Mackay and his student Kendle Maslowski at the Garvan Institute of Medical Research in Sydney focused on a molecule called GPR43. The compound is expressed by cells of the immune system and had previously been shown to bind short−chain fatty acids. It turns out that this molecule acts as an anti−inflammatory receptor: mice that are bred to lack GPR43 have more inflammation than normal mice and cannot fight it off as effectively once it has occurred.

It turns out that this molecule acts as an anti−inflammatory receptor: mice that are bred to lack GPR43 have more inflammation than normal mice and cannot fight it off as effectively once it has occurred.

Because the bacteria in the gut help us break down the fiber that we consume, and produce short−chain fatty acids in the process, it makes sense that upping fiber intake or enhancing the number of bacteria would help combat inflammation.

“Changing diets are changing the kinds of gut bacteria we have, as well as their by−products, particularly short chain fatty acids,” says Maslowski. “If we have low amounts of dietary fibre, 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.” He adds that it is important, from a very early age, to colonize the right kinds of bacteria in the gut. This is done, he says, by eating foods that help support the growth of this friendly flora.

Mackay points out that “The notion that diet might have profound effects on immune responses or inflammatory diseases has never been taken that seriously. 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.” The results of the study appear in the Oct. 29 issue of Nature.

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