Effects of docosahexaenoic acid supplementation on PUFA levels in red blood cells and plasma

Introduction: Polyunsaturated fatty acids (PUFA) are metabolized in a complex network of elongation, desaturation and beta oxidation. Material and methods: The short (1 and 3 wk), and long term (6 and 12 wk) effect of 1076 mg/d docosahexaenoic acid (DHA, free of eicosapentaenoic acid (EPA)) on (absolute) PUFA concentrations in plasma and red blood cells (RBC) of 12 healthy men (mean age 25.1 +/- 1.5 years) was investigated. Results: RBC DHA concentrations significantly (p < 0.001) increased from 28 +/- 1.6 mu g/mL to 38 +/- 2.0 mu g/mL (wk 1), 52 +/- 3.3 mu g/mL (wk 3), 68 +/- 2.6 mu g/mL (wk 6), and 79 +/- 3.5 mu g/mL (wk 12). Arachidonic acid (AA) concentrations declined in response to DHA treatment, while the effect was more pronounced in plasma (wk 0: 183 +/- 9.9 mu g/mL, wk 12: 139 +/- 8.0 mu g/mL,-24%, p < 0.001) compared to RBC (wk 0: 130 +/- 3.7 mu g/mL, wk 12: 108 +/- 4.0 mu g/mL,-16%, p=0.001). Furthermore, an increase of EPA concentrations in plasma (wk 0: 15 +/- 1.5 mu g/mL, wk 1:19 +/- 1.6 mu g/mL, wk 3: 27 +/- 2.3 mu g/mL, wk 6: 23 +/- 1.2 mu g/mL, wk 12: 25 +/- 1.7 mu g/mL, p < 0.001) and RBC (wk 0: 4.7 +/- 0.33 mu g/mL, wk 1: 6.7 +/- 1.3 mu g/mL, wk 3: 8.0 +/- 0.66 mu g/mL, wk 6: 6.9 +/- 0.44 mu g/mL, wk 12: 6.7 +/- 0.45 mu g/mL, n.s.) was observed suggesting a retroconversion of DHA to EPA. Conclusion: Based on PUFA concentrations we showed that DHA supplementation results in increased EPA levels, whereas it is not known if this impacts the formation of EPA-derived lipid mediators. Furthermore, shifts in the entire PUFA pattern after supplementation of EPA or DHA should be taken into account when discussing differential physiological effects of EPA and DHA.