The Effect of Daily Omega-3-Fortified Protein Shakes on O3I and Physical Performance Among Active-Duty Soldiers

Introduction: The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play critical roles in cardiovascular health, cognitive function, and physical recovery—domains essential to military readiness. Service Members fail to meet omega-3 intake guidelines, resulting in a suboptimal Omega-3 Index (O3I) averaging ~4%, well below the 8% associated with protective health benefits. Practical strategies to enhance omega-3 status within operational military settings remain limited. This study evaluated the effect of daily omega-3–fortified protein shakes on O3I and physical performance among active-duty soldiers enrolled in the Army’s Holistic Health and Fitness program. Methods: In this randomized, placebo-controlled trial, 78 soldiers consumed either an omega-3–fortified shake (1600 mg EPA + DHA) or a placebo shake daily, five times a week, for 8 wk. Baseline and post-intervention assessments included O3I measurement, Army Combat Fitness Test (ACFT) performance, and delayed-onset muscle soreness questionnaires. Linear and ordinal regression models controlled for baseline outcomes, age, sex, and race. Results: Fifty-four soldiers completed the study (intervention n = 29; control n = 25). The intervention group demonstrated a significant mean increase in O3I (+0.65%, P = 0.005) relative to controls. The proportion of participants with O3I ≥6% rose from 3% to 15% in the intervention group. No statistically significant differences were found in ACFT or delayed-onset muscle soreness between groups, but within the intervention group, O3I levels showed moderate positive correlations ( r > 0.5) with select ACFT events (deadlift, hand-release pushup, sprint-drag carry). Conclusion: Daily consumption of omega-3–fortified shakes effectively improved omega-3 status among soldiers but did not significantly enhance performance outcomes within the 8-wk timeframe. The intervention group had higher post-intervention O3I levels, and within this group, higher O3I was associated with greater fitness improvements. Findings support incorporating omega-3–fortified products into military nutrition programs, with future research to optimize strategies to reach the target O3I of 8% and evaluate performance effects.