The effects of conjugated linoleic acid supplementation on immune function in healthy volunteers

Objective: To assess the effects of dietary supplementation using two isomeric blends of conjugated linoleic acid (CLA) on immune function in healthy human volunteers. Design: Double-blind, randomised, placebo-controlled intervention trial. Subjects and intervention: A total of 55 healthy volunteers (n = 20 males, n = 35 females) were randomised into one of three study groups who received 3 g/day of a fatty acid blend containing a 50:50 cis-9, trans-11: trans-10, cis-12 CLA isomer blend (2 g CLA), and 80:20 cis-9, trans-11: trans-10, cis-12 (80:20) CLA isomer blend (1.76 g CLA) or linoleic acid (control, 2 g linoleic acid) for 8 weeks. Results: Supplementation with the 80:20 CLA isomer blend significantly (P≤0.05) enhanced PHA-induced lymphocyte proliferation. CLA decreased basal interleukin (IL)-2 secretion (P≤0.01) and increased PHA-induced IL-2 and tumor necrosis factor α (TNFα) production (P≤0.01). However, these effects were not solely attributable to CLA as similar results were observed with linoleic acid. CLA supplementation had no significant effect on peripheral blood mononuclear cells IL-4 production, or on serum-soluble intercellular adhesion molecule-1 (slCAM-1) or plasma prostaglandin E₂ (PGE₂) or leukotreine B₄ (LTB₄) concentrations. Conclusions: This study shows that CLA supplementation had a minimal effect on the markers of human immune function. Furthermore, supplementation with CLA had no immunological benefit compared with linoleic acid.