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Peter G. Dentone, Maureen G. Maguire, Ellen Peskin, Ann Moser, Penny A. Asbell; RBC Fatty Acids Analysis for Determining Compliance with Omega-3 Supplements. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4318.
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To assess subject compliance with oral omega-3 fatty acids (ω-3FA) supplements (fish oil) and placebo (olive oil) using pill counts and red blood cell (RBC) membrane total lipid FA profiles and to compare the 2 assessment techniques.
16 Subjects were given oral ω-3FA supplements or placebo (5 capsules/day) for 3 months. All subjects were instructed to return any unused capsules at the end of 3 months. Blood drawn at baseline and 3 months was analyzed in a masked fashion for RBC membrane total lipid FA content. Blood was collected in 4mL tubes containing EDTA and analyzed the next day for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels (% total FA), for arachidonic acid (AA) which is replaced by EPA and DHA in the cell membrane, and for oleic acid (OA) levels (% total FA) present in olive oil. Wilcoxon signed-rank tests and rank-sum tests were used to compare changes from baseline and to compare the between treatment groups; Spearman correlation coefficients were used to assess the relationship of pill counts to changes in FAs.
Pill counts for the ω-3 (N=7) and placebo (N=9) groups showed a mean consumption of 4.39 and 4.76 pills / day, respectively. In the ω-3 group, the median change from baseline was +1.46% for EPA (p=0.03), +1.49% for DHA (p=0.08), -1.91% for AA (p=0.02), and -0.50 for OA levels (p=0.11). In the placebo group, median changes in all measured FAs were small and not statistically significant (EPA: 0.05%, p=0.25; DHA: 0.25%, p=0.43; AA: -0.23%, p=0.16; OA: -0.60%, p=0.16). Changes in FA levels were significantly greater in the ω-3 group for EPA (p=0.01) and AA (p=0.04). The correlations between the number of pills taken in the ω-3 group and changes in EPA (r=0.36, p=0.43) and DHA (r=0.17, p=0.70) levels were not strong.
Both groups showed good compliance as measured by pill counts with no significant difference. Subjects in the ω-3 group showed increases in EPA (significant) and DHA (not significant) along with a significant decrease in AA, as expected. These trends were not seen in the placebo group. The low correlation between pill counts and blood levels suggests pill counts alone do not accurately capture compliance and are not a replacement for blood tests in assessment of compliance in studies of ω-3 supplements.
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