Soluble Fiber Boosts Immune System

URBANA, Ill.Soluble fiber reduces the inflammation associated with obesity-related diseases and strengthens the immune system by increasing the production of an anti-inflammatory protein called interleukin-4, according to a new study from the University of Illinois.

"Soluble fiber changes the personality of immune cellsthey go from being pro-inflammatory, angry cells to anti-inflammatory, healing cells that help us recover faster from infection," said Gregory Freund, a professor in the U of I's College of Medicine and a faculty member in the College of Agriculture, Consumer and Environmental Sciences' Division of Nutritional Sciences.

Researchers studied laboratory mice that consumed low-fat diets that were identical except that they contained either soluble or insoluble fiber. After six weeks on the diet, the animals had distinctly different responses when the scientists induced illness by introducing a substance (lipopolysaccharide) that causes the body to mimic a bacterial infection.

"Two hours after lipopolysaccharide injection, the mice fed soluble fiber were only half as sick as the other group, and they recovered 50-percent sooner. The differences between the groups continued to be pronounced all the way out to 24 hours," said researcher Christina Sherry. "In only six weeks, these animals had profound, positive changes in their immune systems.

Findings revealed that soluble fiber has direct anti-inflammatory effects and builds up the immune system, and the amount of soluble fiber necessary to achieve these health benefits is a reasonable, not a pharmacological, amount.

The recommended daily dietary recommendation is 28 g to 35 g of total fiber, but most of FDA's health claims are for insoluble fiber, and that's where things get a bit complicated, Sherry said.

"Not all fiber is created equal, although you wouldn't know that by reading nutrition labels," she said. "Most manufacturers don't tell you how much of each type of fiber a food contains, and we think it's important that this information be included on a product's packaging."

Good sources of soluble fiber are oat bran, barley, nuts, seeds, lentils, citrus fruits, apples, strawberries and carrots. Insoluble fiber, found in whole-wheat and whole-grain products, wheat bran, and green, leafy vegetables, is also valuable for providing bulk and helping food move through the digestive system, but it doesn't provide the boost to the immune system that soluble fiber provides.