RBC and WBC fatty acid composition following consumption of an omega 3 supplement: lessons for future clinical trials

Abstract

Background: Results from increasing numbers of in vitro and in vivo studies have demonstrated that omega 3 fatty acids incorporated in cell culture media or in the diet of the animals can suppress the growth of cancers. When human clinical trials are initiated to determine the ability of omega 3 fatty acids to alter growth or response to chemotherapeutic interventions of cancers, it will be essential to determine the omega 3 intake of individuals in the trial to determine compliance with consumption of the supplement and to correlate with endpoints of efficacy. We wondered if the fatty acid composition of RBCs might accurately indicate incorporation of omega 3 fatty acids in the WBCs. In this report we determine and compare the changes in fatty acid compositions of red blood cells and white blood cells in response to consumption of three doses of an omega 3 fatty acid supplement.

Results: We found that the fraction of omega 3 fatty acids in both red blood cells and white blood cells increased following consumption of the supplement. There was a linear, dose responsive increase in the fraction of omega 3 fatty acids in red blood cells but the increase in omega 3 in white blood cells was not linear. The magnitude of increase in omega 3 fatty acids was different between the two cell types.

Conclusions: Fatty acid analysis of red blood cells is a good measure of compliance with supplement consumption. However, fatty acid analysis of white blood cells is needed to correlate changes in fatty acid composition of white blood cells with other biochemical changes in the white blood cells.

Trial registration: ClinicalTrials.gov NCT00899353.

Figures

Figure 1

Baseline composition of red and white blood cells. The % compositions (mean ± SEM) of ten assayed lipids at baseline (without omega 3 supplement) of red and white blood cells are shown. Two way analyses of variance followed by Bonferroni posttests showed that the steric acid fraction was significantly less and the arachidonic acid fraction was significantly higher in red blood cells than in white blood cells at baseline. EPA - eicosapentaenoic acid; DPA - docosapentaenoic acid; DHA - docosahexaenoic acid.

Figure 2

Lipid composition of red blood cells. The % compositions (mean ± SEM) of ten assayed lipids are shown. Omega 6 and omega 3 species are identified by the bracket over the top of each set. Repeated measures analyses of variance followed by Bonferroni posttests were used to determine significant changes from the baseline fraction of each fatty acid. Significant differences from baseline following each dose of omega 3 supplement are shown by: * - p < 0.05; ** p < 0.01; *** - p < 0.001. EPA - eicosapentaenoic acid; DPA - docosapentaenoic acid; DHA - docosahexaenoic acid.

Figure 3

Lipid composition of white blood cells. The % compositions (mean ± SEM) of ten assayed lipids are shown. Omega 6 and omega 3 species are identified by the bracket over the top of each set. Repeated measures analyses of variance followed by Bonferroni posttests showed that there were no significant changes from the baseline fraction of individual fatty acids. EPA - eicosapentaenoic acid; DPA - docosapentaenoic acid; DHA - docosahexaenoic acid.

Figure 4

Change in total omega 3 in red and white blood cells. The change in the sum of % compositions of omega 3 fatty acids in red or in white blood cells following consumption of 3, 6 or 9 capsules of omega 3 supplement for one month is shown. A. Linear regression was used to determine the dose responsive change in omega 3 fatty acids in red or white blood cell membranes. For red blood cells, there was a significant linear regression, r2 = 0.99, slope = 1.17%/capsule. The regression fit was not significant for white blood cells. The correlation coefficient for a best fit line was 0.77 with a slope of 0.47%/capsule. B. Non-linear regression was a better fit to the change in lipid composition of white blood cells.