Plasma omega-3 fatty acids are not associated with muscle strength, regardless of age or protein intake: National Health and Nutrition Examination Survey 2011-12.

Background & aims: Muscle strength is a key predictor of both quality of life and mortality. Although numerous studies have investigated the relationship between omega-3 (ω-3) intake and muscle strength, the evidence remains inconclusive. Furthermore, it is unclear whether this association is influenced by protein intake. Therefore, the aim of this study was to evaluate the potential associations between plasma ω-3 levels (as a biomarker of ω-3 intake) and muscle strength across different age ranges and levels of protein intake.

Method: A cross-sectional study was conducted involving 1708 individuals aged 20-80 years from the 2011-2012 National Health and Nutrition Examination Survey (NHANES). Plasma levels of total ω-3 fatty acids and their subtypes-alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)-were measured using chromatography-mass spectrometry. Muscle strength was assessed using handgrip strength, with the combined grip strength of both hands being analyzed. Dietary intake was evaluated using two 24-h recalls, and usual intake was estimated using the National Cancer Institute method. Linear regression analyses were conducted to examine the associations between plasma ω-3 fatty acids and muscle strength, stratified by age groups (<60 years and ≥60 years) and protein intake categories (<0.8 g/kg/day, ≥0.8-<1.2 g/kg/day, and ≥1.2 g/kg/day), while adjusting for potential confounders.

Results: Total plasma ω-3, ALA, EPA, and DHA were not associated with muscle strength in the total sample, regardless of protein intake levels. This lack of association remained consistent across all age groups and protein intake strata.

Conclusion: Plasma ω-3 fatty acids were not associated with muscle strength, regardless of age or protein intake. Overall, these findings suggest that plasma ω-3 fatty acids may not play a significant role in muscle strength.