Measurement of Omega-3 Fatty Acids More Reliable in Red Blood Cells Than in Plasma

Investigators at Health Diagnostic Laboratory, Inc. (Richmond, VA, USA) compared the affect of dietary fish oil and fish oil supplements on measurement of blood omega-3 fatty acid levels in a study population comprising 20 healthy volunteers.

The volunteers were given four capsules containing 3.6 grams of omega-3 fatty acids alongside a standard breakfast. Blood samples were drawn six times over the course of 24 hours, and the investigators monitored eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels in plasma and red blood cells. At six hours after capsule intake, the plasma concentration of EPA and DHA had increased by 47%, while the plasma EPA and DHA percentage of total fatty acids increased by 19%. In contrast, levels of EPA and DHA in red blood cells did not change from baseline values. By 24 hours after capsule intake, plasma EPA and DHA levels were 10-fold greater than those in red blood cells.

"Although some experts question the value of omega-3 fatty acid supplementation for reducing risk of coronary heart disease, medical testing for omega-3 fatty acid status has become more common and clinicians have a choice of whether to use red blood cell or plasma-based assays," said senior author Dr. William S. Harris, a senior research scientist at Health Diagnostic Laboratory, Inc. "While different assays have different performance characteristics, fasting requirements, and sensitivities, it is important for clinicians to choose the appropriate testing method. This research backs our hypothesis that the red blood cell omega-3 assay is the preferred sample type for the assessment of fatty acids in the body."

The study was published in the May 9, 2013, online edition of the Journal of Clinical Lipidology.

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