Apple's soluble fiber boosts immune system

by S. C.

A new University of Illinois study touts the benefits of soluble fiber -- found in oats, apples, and nuts, for starters -- saying that it reduces the inflammation associated with obesity-related diseases and strengthens the immune system.

Soluble fiber causes increased production of an anti-inflammatory protein called interleukin-4, he said.

The study will appear in the May 2010 issue of Brain, Behavior, and Immunity and is available online now.

In the experiment, laboratory mice 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.

Scientists have long known that obesity is linked to inflammatory conditions, such as diabetes and heart disease.

Yet, in a recent study, the U of I scientists demonstrated that fat tissue produces hormones that appear to compensate for this inflammation. "There are significant anti-inflammatory components in fat tissue and, if they were strategically unleashed, they could potentially protect obese people from further inflammatory insults, such as a heart attack or stroke. In obese animals, you can see the body compensating in an effort to protect itself," he said.

Not all fat is bad, the researcher noted. The Mediterranean diet, which receives high marks for its health benefits, includes such foods as olive oil; salmon, tuna, sardines, and trout, which contain important omega-3 and -6 fatty acids; and plant sources of fat, such as flaxseed.

The recommended daily dietary recommendation is 28 to 35 grams of total fiber, but most of the FDA's health claims are for insoluble fiber.

Good sources of soluble fiber are oat bran, barley, nuts, seeds, lentils, citrus fruits, apples, strawberries, and carrots. "We used a citrus-based pectin in our study," Sherry said.

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.