The Dose–Response Effect of Docosahexaenoic Acid on the Omega-3 Index in American Football Athletes

American-style football (ASF) players are at increased risk for head injuries and cardiovascular disease. n-3 polyunsaturated fatty acids are cardioprotective, and emerging evidence suggests benefits for protection against head injuries. However, fundamental knowledge of n-3 polyunsaturated fatty acid dosing in athletes such as ASF players remains poorly understood. Therefore, this study investigated the dose-response effect of docosahexaenoic acid (DHA) supplementation in red blood cells (RBC) and as the Omega-3 Index (O3I), in collegiate ASF players throughout a competitive season. Sixty-nine ASF players were randomly assigned placebo (corn oil), or 2, 4, or 6 g·d -1 of DHA supplement. Blood samples were collected at eight time points (T1-T8) over 27 wk. RBC were extracted and analyzed by gas-liquid chromatography. Compliant players who had samples collected at all time points were analyzed. A repeated-measures ANOVA was conducted to assess the dose-response effect of DHA over time, and between-group differences at individual time points were assessed by one-way ANOVA followed by Tukey post hoc test. A significant dose and time interaction was found, and all supplement groups had significantly greater DHA in RBC compared with placebo from T2-T8 ( P < 0.05). Athletes receiving 6 g·d -1 of DHA had the greatest O3I, relative to other groups, and the O3I reached steady state by 15 wk. The 6 g·d -1 group surpassed >8% on the O3I at approximately twice the rate of the 4 g·d -1 group (8 vs 15 wk). Our findings provide important fundamental knowledge demonstrating a dose-response incorporation of DHA into RBC membranes up to 6 g·d -1 . Furthermore, 6 g·d -1 of DHA can be used to rapidly achieve a desired O3I (>8%) in athletes in only 8 wk.