Influence of dietary interventions on the immune system: an investigation of the impact of omega-3 fatty acids, dietary fermentable materials and high energy diets
Clarke, Sandra T.
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Dietary interventions vary in ability to influence immune activity. Separate investigations were conducted to determine the immune impact of omega-3 fatty acids, dietary fermentable materials (DFM) and high energy (HE) diets. Omega-3 fatty acid impact on bovine immunity was examined by comparing effects of fish oil and microalgae dietary supplements in the context of different feed management systems (pasture versus confinement). Cattle consuming microalgae had higher antibody production and cattle in the pasture system had higher anti-keyhole limpet hemocyanin (KLH) and total antibody responses on all diets. Overall, effects of omega-3 supplements on bovine immunity were influenced by feed management system with heightened impact on antibody production observed with a pasture system. A double-blind placebo-controlled, randomized crossover clinical trial involving 30 healthy adults was conducted to examine impacts of β2-1 fructans on immunity. Subjects consumed an oligofructose-enriched inulin or maltodextrin supplement for a 28-day period (5 g, 3× daily with meals). β2-1 fructan supplementation significantly increased serum endotoxin and IL-4 concentrations, circulating percentages of CD282+/TLR2+ myeloid Dendritic cells (mDC) and ex vivo responsiveness to a Toll-like receptor 2 (TLR2) agonist, while serum IL-10 concentrations decreased. A rat trial was designed to examine effects of a HE diet supplemented with varied DFM (7% wheat bran, oat bran, resistant starch type II, or fructooligosaccharide (FOS)) on obesity-associated biomarkers in male Sprague-Dawley rats. After 2 weeks of HE diet consumption, rats were segregated into obese-prone and obese-resistant phenotypes and shifted to DFM-supplemented HE diets for an additional 11-12 weeks. Obese-prone rats had higher serum insulin and leptin concentrations than obese-resistant rats. FOS-fed rats had decreased splenic percentages of B cells, natural killer cells, T lymphocytes, memory T cells and cytotoxic T cells compared to rats on the control diet. High-energy diets had differential impacts on systemic and mucosal cytokines in both phenotypes; however, DFM had relatively less influence on cytokine and adipokine profiles associated with diet-induced obesity. Taken together, dietary interventions are capable of subtly influencing varied immune outcomes in animal models and in human subjects, however the interpretation of these dietary influences may be context-dependent.