HDL, Inc. Researchers Compare Effects of Acute Fish Oil Dose on Plasma vs. Red Blood Cell Fatty Acid Levels

RICHMOND, Va., July 1, 2013 /PRNewswire/-- An acute dose of omega-3 fatty acids found in oily fish or fish oil supplements can significantly elevate levels of omega-3 in plasma but not in red blood cells, according to a study in press with the Journal of Clinical Lipidology. The findings show that red blood cells (RBCs) offer physicians a more stable estimate of a patient's omega-3 levels in the blood than plasma.

For the study conducted by researchers at Health Diagnostic Laboratory, Inc., 20 healthy 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 as researchers monitored EPA and DHA levels in plasma and red blood cells to look at fatty acid changes over time in these different blood fractions. At six hours, the plasma concentration of the EPA and DHA had increased by 47%, while the plasma EPA and DHA percent of total fatty acids increased by 19%. Meanwhile, EPA and DHA composition in red blood cells was unchanged in those same six hours. By 24 hours, the change in the plasma EPA and DHA markers was 10-fold greater than that in RBCs.

"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 William S. Harris, HDL, Inc. Senior Research Scientist and the study's lead author. "While different assays have different performance characteristics, fasting requirements, and sensitivities, it's important for clinicians to choose the appropriate testing method. This research backs our hypothesis that the RBC omega-3 assay is the preferred sample type for the assessment of fatty acids in the body."

Dr. Joseph McConnell, HDL, Inc. Chief Laboratory Officer and co-author on the study, compared the RBC test method to hemoglobin A1c (HbA1c). "It's well known that HbA1c is preferable to plasma glucose as a long-term marker of glucose levels," he said. "We believe the same may be true of the RBC omega-3 test. Importantly, the RBC omega-3 test can be done in fasting or fed blood samples, but plasma omega-3 should only be measured in fasting samples."

Even fasting-state plasma levels may not give a true reflection of omega-3 status, McConnell said. "A prolonged fast could lead to underestimation of omega-3 fatty acid status, while an insufficiently long fast could lead to overestimation," he said. "Our study demonstrates that RBC fatty acid measures reflect fatty acid status accurately in all fasting and non-fasting states."

Many patients are told to increase their intake of fish oil through either fish or fish oil supplements after a blood test reveals suboptimal omega-3 fatty acid levels. While some patients comply, others do not, and may choose to take a single large dose of fish oil within 24 hours prior to a doctor's appointment in an effort to improve blood levels and appear compliant with the physician's recommendations. When blood is drawn at the appointment, their omega-3 levels in plasma will be elevated and could mislead the physician, but the RBC level should be unchanged, reflecting the true chronic condition.

The full study is in press with the Journal of Clinical Lipidology and is available early at the following link: http://bit.ly/rbcplasmahdlinc.

About Health Diagnostic Laboratory, Inc.
Health Diagnostic Laboratory, Inc. (HDL, Inc.) is a leader in health management offering a comprehensive test menu of risk factors and biomarkers for cardiovascular disease, diabetes, and related diseases. HDL, Inc.'s systematic approach identifies factors contributing to disease and provides information for effective treatment, allowing physicians to more effectively manage patients. Individuals receive a personalized overview of their risk factors along with intensive counseling from Clinical Health Consultants, generally at no additional cost, to improve compliance with physician treatment recommendations. HDL, Inc. is a CLIA-certified, CAP-accredited laboratory. For more information, visit myhdl.com.

SOURCE Health Diagnostic Laboratory, Inc.