Effects of protein–carbohydrate vs. carbohydrate alone supplementation on immune inflammation markers in endurance athletes: a randomized controlled trial

Purpose The impact of ingesting carbohydrates alone or combined with proteins to support exercise immune adaptation in endurance athletes is scarcely investigated. The present study compares the effect of ingesting a combined protein–carbohydrate supplement vs. a carbohydrate-only supplement post-workout on immune inflammation markers following a 10 week periodized endurance training program in well-trained athletes. Methods Twenty-five men completed the study after being randomly assigned to one of the following intervention groups: combined protein–carbohydrate (PRO-CHO n = 12, 31 ± 9 years, V˙ O2peak 61.0 ± 5.6 ml.kg−1.min−1) or non-protein isoenergetic carbohydrate (CHO, n = 13, 33 ± 8 years, V˙ O2peak 60.6 ± 6.9 ml.kg−1.min−1). Treatment consisted of ingesting 24 g of assigned supplement, mixed with 250 ml of orange juice, once a day for 10 weeks immediately post-workout (or before breakfast on non-training days). Measurements were conducted pre- and post-intervention on total leukocytes, leukocyte subsets (i.e., neutrophils, eosinophils, basophils, monocytes, and lymphocytes), and platelets. The inflammatory status was assessed by the neutrophil-to-lymphocyte ratio (NLR), the platelet-to-lymphocyte ratio (PLR), and the systemic-immune inflammation index (SII). Results Post-intervention, significant increases were observed for CHO group only for the three inflammatory markers: NLR (p = 0.050, d = 0.58), PLR (p = 0.041, d = 0.60), and SII (p = 0.004, d = 0.81) but not for PRO-CHO (p > 0.05). Conclusion Ingesting a post-workout protein–carbohydrate combined beverage promoted a more favourable immune status than carbohydrate-only ingestion by attenuating cellular inflammation over a 10 week training period in endurance male athletes. Trial Registration The study was registered in ClinicalTrials.gov with the following ID: NCT02954367. The study was registered by 3 November 2016.