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

•Short term (1 and 3 wk) effects of DHA intake (1076 mg/d) on FA profiles.•Long term (6 and 12 wk) effects of DHA intake on FA profiles.•Massive increase of DHA levels in plasma and red blood cells.•Slightly, but significantly increased EPA levels in plasma.•Estimated %-retroconversion rate: 13.2, 12.0, 5.3, and 3.3 after 1, 3, 6, and 12 wk.

IntroductionPolyunsaturated fatty acids (PUFA) are metabolized in a complex network of elongation, desaturation and beta oxidation.Material and methodsThe 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.ResultsRBC DHA concentrations significantly (p<0.001) increased from 28±1.6 µg/mL to 38±2.0 µg/mL (wk 1), 52±3.3 µg/mL (wk 3), 68±2.6 µg/mL (wk 6), and 79±3.5 µg/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 µg/mL, wk 12: 139±8.0 µg/mL, −24%, p<0.001) compared to RBC (wk 0: 130±3.7 µg/mL, wk 12: 108±4.0 µg/mL, −16%, p=0.001). Furthermore, an increase of EPA concentrations in plasma (wk 0: 15±1.5 µg/mL, wk 1:19±1.6 µg/mL, wk 3: 27±2.3 µg/mL, wk 6: 23±1.2 µg/mL, wk 12: 25±1.7 µg/mL, p<0.001) and RBC (wk 0: 4.7±0.33 µg/mL, wk 1: 6.7±1.3 µg/mL, wk 3: 8.0±0.66 µg/mL, wk 6: 6.9±0.44 µg/mL, wk 12: 6.7±0.45 µg/mL, n.s.) was observed suggesting a retroconversion of DHA to EPA.ConclusionBased 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.