Comparative effects of an acute dose of fish oil on omega-3 fatty acid levels in red blood cells versus plasma: implications for clinical utility.
BACKGROUND
Omega-3 fatty acid (n-3 FA) biostatus can be estimated with red blood cell (RBC) membranes or plasma. The matrix that exhibits the lower within-person variability and is less affected by an acute dose of n-3 FA is preferred in clinical practice.


OBJECTIVE
We compared the acute effects of a large dose of n-3 FA on RBC and plasma levels of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA).


METHODS
Healthy volunteers (n = 20) were given 4 capsules containing 3.6 g of n-3 FA with a standardized breakfast. Blood samples were drawn at 0, 2, 4, 6, 8, and 24 hours. The EPA + DHA content of RBC membranes and plasma (the latter expressed as a percentage of total FA and as a concentration) were determined. General linear mixed models were used to analyze the mean response profiles in FA changes over time for plasma and RBCs.


RESULTS
At 6 hours after load, the plasma concentration of EPA + DHA had increased by 47% (95% confidence interval [CI], 24% to 73%) and the plasma EPA + DHA percentage of total FA by 19% (95% CI, 4.7% to 36%). The RBC EPA + DHA percentage of composition was unchanged [-0.6% (95% CI, -2.6% to 1.5%)]. At 24 hours, the change in both of the plasma EPA + DHA markers was 10-fold greater than that in RBCs.


CONCLUSIONS
An acute dose of n-3 FA (eg, a meal of oily fish or fish oil supplements) taken within a day before a doctor's visit can elevate levels of EPA + DHA in plasma, whether expressed as a percentage or a concentration, but not in RBC membranes. Similar to hemoglobin A1c, which is not affected by an acute glycemic deviation, RBCs provide a more reliable estimate of a patient's chronic EPA + DHA status than does plasma.
Health Diagnostic Laboratory, Inc, 737 N 5th Street, Suite 103, Richmond, VA 23219, USA; OmegaQuant Analytics, LLC, Sioux Falls, SD, USA; Department of Internal Medicine, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD, USA. Electronic address: Bharris@hdlabinc.com.
William S
WS
Harris
Stephen A
SA
Varvel
James V
JV
Pottala
G Russell
GR
Warnick
Joseph P
JP
McConnell
D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods*; D004281:Docosahexaenoic Acids / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D015118:Eicosapentaenoic Acid / Q000097:blood*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005395:Fish Oils / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010949:Plasma / Q000187:drug effects / Q000378:metabolism*
D005395:Fish Oils; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid
Biomarker; Biovariability; Erythrocytes; Plasma; n-3 Fatty acids