How DHA and EPA Contribute to the Omega-3 Index

June 21, 2021

The Omega-3 Index is the proportion of combined EPA and DHA in red blood cell (RBC) membrane phospholipids, and it is known to reflect phospholipid composition in the heart and other organs. A higher Omega-3 Index is associated with reduced coronary mortality and disease risk, but the relative contributions of EPA and DHA to this marker of cardiovascular health have not previously been investigated.

This team of researchers present their concern that levels of DPA, a lesser-known omega-3 fat, are not included in calculating the Omega-3 Index. Like DHA, DPA bears a conjugated 22-carbon tail, and DPA levels in RBCs have been linked to lower circulating levels of C-reactive protein (an inflammatory marker) and triglycerides in healthy adults. Conversely, lower tissue, serum, or plasma DPA has been associated with greater overall and cardiovascular mortality as well as higher risk for acute myocardial infarction and fatal coronary heart disease.

For this study, 154 men and women with abdominal obesity (based on waist circumference) and mild-to-moderately elevated C-reactive protein levels were randomized to a crossover series of three daily treatments (2.7 g EPA, 2.7 g DHA, or a corn oil control) for a median of 10 weeks each, in random sequence and separated by a 9-week washout period. Diets were controlled to exclude other dietary omega-3 fats, and study participants were assessed for Omega-3 Index,RBC levels of DPA, blood lipid profiles, and gene expression related to omega-3 fat metabolism after each treatment period.