Moderate levels of linolenic acid (GLA) and eicosapentaenoic acid (EPA) can decrease mitogen-stimulated lymphocyte proliferation according to a study released this week. Scientists at Oxford University, in collaboration with the Food Science and Human Nutrition departments of the Universities of Reading and Southampton, investigated the effect of dietary supplementation with ALNA, -linolenic acid (GLA), arachidonic acid (ARA), DHA or FO on the proliferation of mitogen-stimulated human peripheral blood mononuclear cells (PBMC) and on the production of cytokines by those cells. Healthy subjects aged between 55-75 years old consumed nine capsules for 12 weeks; the capsules contained placebo oil (an 80:20 mix of palm and sunflower seed oils) or blends of placebo oil with oils rich in ALNA, GLA, ARA or DHA or FO. Subjects in these groups consumed 2 g of ALNA or 770 mg of GLA or 680 mg of ARA or 720 mg of DHA or 1 g of EPA plus DHA (720 mg of EPA + 280 mg of DHA) daily from the capsules. Total fat intake from the capsules was 4 g/d. The fatty acid composition of PBMC phospholipids was significantly changed in the GLA, ARA, DHA and FO groups however lymphocyte proliferation was not significantly affected by the placebo, ALNA, ARA or DHA treatments. The scientists found that GLA and FO caused a significant decrease (up to 65 per cent) in lymphocyte proliferation. This decrease was partly reversed after stopping the supplementation. Leading study researcher, Dr. F. Thies, concluded in the July issue of the Journal of Nutrition that a moderate level GLA or EPA but not of other (n-6) or (n-3) PUFA can decrease mitogen-stimulated lymphocyte proliferation but not production of interleukin-2 or interferon-. Source: Journal of Nutrition 2001;131:1918-1927.