Lab animals fed a low-fat diet with either soluble or insoluble fibre showed distinctly different responses when their immune system was challenged, with the soluble-fibre-fed animals displaying the less sickness and a faster recovery rate than the other animals, according to findings published in Brain, Behavior, and Immunity.
Researchers from the University of Illinois noted that the study shows that soluble fibre has a direct anti-inflammatory effect and promotes immune health, with the changes observed being achieved with reasonable, and not pharmacological, doses.
Chronic inflammation has been linked to range of conditions linked to heart disease, osteoporosis, cognitive decline and Alzheimer's, type-2 diabetes, and arthritis.
The researchers are now considering if the benefits are extended when high-fat diets are consumed. The idea here would be to test if soluble fibre may counter some of the negative effects of a high-fat diet, essentially immunizing obese persons against the harmful effects of fat.
"Now we'd like to find a way to keep some of the anti-inflammatory, positive effects that develop over time with a high-fat diet while reducing that diet's negative effects, such as high blood glucose and high triglycerides. It's possible that supplementing a high-fat diet with soluble fibre could do that, even delaying the onset of diabetes," said Professor Gregory Freund, lead researcher of the study.
Not all fibres are created equal
In Europe and Japan, soluble fibre has the greater market share than insoluble. In the US, where the entire fibre market was worth $192.8m (€151.0m) in 2004, insoluble fibre dominates the market with $176.2m (€138.0m), and $16.6m (€13.0m) soluble.
But while Frost and Sullivan predicts overall growth in the US to $470m (€369m) by 2011, the soluble fibre sector is expected to increase by almost twice the compound annual growth rate (CAGR) compared to insoluble fibre - 26.3 per cent compared to 13.1 per cent.
Freund and his co-workers fed low-fat diets supplemented with either soluble (pectin, 10 per cent of the diet) or insoluble fibre (cellulose, 5 or 10 per cent of the diet) for six weeks. At the end of this period the mice were challenged with an endotoxin to induce sickness.
“Two hours after [entotoxin] injection, the mice fed soluble fibre were only half as sick as the other group, and they recovered 50 per cent sooner. And the differences between the groups continued to be pronounced all the way out to 24 hours," said Christina Sherry, co-researcher on the study.
“In only six weeks, these animals had profound, positive changes in their immune systems,” she added.
The benefits were reportedly linked to an increased production of the anti-inflammatory protein interleukin-4 (IL-4), said the researchers.
“Our data also highlights the potential detrimental nature of a diet lacking pectin especially as related to the response of the brain to infectious disease,” concluded the reearchers.
Source: Brain, Behavior, and Immunity
Published online ahead of print, doi: 10.1016/j.bbi.2010.01.015
"Sickness behavior induced by endotoxin can be mitigated by the dietary soluble fiber, pectin, through up-regulation of IL-4 and Th2 polarization"
Authors: C.L. Sherry, S.S. Kim, R.N. Dilger, L.L. Bauer, M.L. Moon, R.I. Tapping, G.C. Fahey Jr., K.A. Tappenden, G.G. Freund