Abstract
Consumption of oily fish is sporadic, whereas controlled intervention studies of n–3 (ω-3) fatty acids usually provide capsules containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as a daily dose. This methodologic study explored whether there are differences in the short-, medium-, and long-term incorporation of EPA and DHA into blood plasma and cells with the provision of identical amounts of EPA and DHA, equivalent to 2 oily fish servings per week (or 6.54 g/wk EPA and DHA), either intermittently (i.e., 1 portion twice per week) or continuously (i.e., divided into daily amounts). The study was part of a randomized, double-blind controlled intervention lasting 12 mo, with participants stratified by age and sex. There were 5 intervention groups, 2 of which are reported here: the 2 intermittent portions (2I) and 2 continuous portions (2C) groups. EPA and DHA were measured in plasma phosphatidylcholine, platelets, and blood mononuclear cells (MNCs) at 9 time points. Sixty-five participants completed the study (2I group, n = 30, mean age of 49.2 y; 2C group, n = 35, mean age of 50.6 y). The incorporation pattern over the 12-mo intervention was different between the 2 groups in all samples (P < 0.0001, time × treatment interaction). At the end of the 12-mo intervention, the 2C group had higher EPA, DHA, and EPA + DHA in platelets (all P < 0.01) and higher EPA and EPA + DHA in MNCs (both P < 0.05) compared with the 2I group. No significant differences were shown for plasma phosphatidylcholine EPA (P = 0.1), DHA (P = 0.15), EPA + DHA (P = 0.07), or MNC DHA (P = 0.06). In conclusion, the pattern of consumption does affect the incorporation of EPA and DHA into cells used as biomarkers of intake. The differences identified here need to be considered in the design of studies and when extrapolating results from continuous capsule-based intervention studies to dietary guidelines for oily fish consumption. This trial was registered at www.controlled-trials.com> as ISRCTN48398526.
Highlights
There is good epidemiologic evidence to support the positive effect of the consumption of oily fish in reducing risk of disease, including all-cause mortality, cardiovascular disease [1,2,3,4], Manuscript received October 16, 2013
We identified that plasma phosphatidylcholine eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was the best marker of short-term changes in intake, platelets as a medium-term marker of intake, and blood mononuclear cells (MNCs)8 as a long-term marker of intake [15]
Analysis of baseline FA status in plasma phosphatidylcholine, MNCs, and platelets showed no significant differences in the proportion of EPA or DHA between the 2 intermittent portions (2I) and 2 continuous portions (2C) groups (Table 1)
Summary
There is good epidemiologic evidence to support the positive effect of the consumption of oily fish in reducing risk of disease, including all-cause mortality, cardiovascular disease [1,2,3,4], Manuscript received October 16, 2013. The provision of EPA and DHA during supplementation studies differs from that of dietary intake, with oily fish being consumed sporadically in most populations. Supplements providing EPA and DHA are typically taken daily. This difference in the pattern of delivery of EPA and DHA may alter the uptake and enrichment of EPA and DHA into the blood, cells, and tissues. Most of the evidence on which dietary recommendations are based is derived from supplementation studies, yet a difference in uptake and incorporation could have implications for the interpretation of these data and the subsequent translation to public health advice, which is usually given in terms of portions of oily fish per week
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