The omega-3 index represents the red blood cell (RBC) content of two major long-chain n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid, and docosahexaenoic acid. We sought to determine factors associated with a favorable response to fish oil treatment and to characterize changes in RBC PUFAs associated with fish oil supplementation.
This study was a secondary analysis of the OMEGA-PAD I trial, a randomized, double-blinded, placebo-controlled trial investigating short-duration, high-dose n-3 PUFA oral supplementation on endothelial function and inflammation in subjects with peripheral arterial disease. Patients with mild to severe claudication received either 4.4 g of fish oil providing 2.6 g of eicosapentaenoic acid and 1.8 g of docosahexaenoic acid daily (n = 40) or placebo capsules (n = 40) for 1 mo. The RBC fatty acid content was measured by gas chromatography and expressed as a percent of total fatty acids. The change in omega-3 index was calculated as the difference between pre- and post-supplementation in the fish oil and placebo groups. Univariate analysis identified predictors of change in omega-3 index, with these variables included in our multivariable model.
In the fish oil group, there was an increase in the omega-3 index (5.1┬▒ 1.3% to 9.0┬▒ 1.8%; P < 0.0001), whereas there was no change in the control group. Factors associated with a favorable response (i.e., greater than the median change of 4.06%) included a lower body mass index and higher concentrations of low-density lipoproteins. Other demographic and/or lifestyle factors such as age, race, or smoking status were unrelated to the response. Oral n-3 PUFA supplementation also decreased the n-6 PUFA content in RBCs.
Short-term, high-dose n-3 PUFA supplementation increases the omega-3 index to a greater extent in patients with a lower body mass index and higher total and low-density lipoprotein cholesterol levels.

PMID: 28457318

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This study was conducted using Nordic Naturals ProOmega/Ultimate Omega product.