Do multi-ingredient protein supplements augment resistance training-induced gains in skeletal muscle mass and strength? A systematic review and meta-analysis of 35 trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 30824459 · doi:10.1136/bjsports-2018-099889
What was done
A systematic review and random-effects meta-analysis was conducted across MEDLINE, Embase, CINAHL, and SPORTDiscus to determine the effects of multi-ingredient protein (MIP) supplements compared to protein-only (PRO) or placebo supplementation during resistance exercise training (RT) lasting at least 6 weeks. Outcomes assessed included fat-free mass (FFM), fat mass, and 1-repetition maximum (1RM) upper- and lower-body muscular strength, with subgroup analyses by training status and chronological age.
What was found
Across 35 trials involving 1,387 participants (most common additives being creatine [n=17] or vitamin D [n=10]), MIP supplementation compared with all non-MIP controls resulted in significant (p < 0.05) increases in FFM (0.80 kg, 95% CI 0.44 to 1.15), 1RM lower-body strength (4.22 kg, 95% CI 0.79 to 7.64), and 1RM upper-body strength (2.56 kg, 95% CI 0.79 to 4.33). Subgroup analyses showed greater FFM gains from MIP in untrained (0.95 kg, 95% CI 0.51 to 1.39, p < 0.0001) and older adults (0.77 kg, 95% CI 0.11 to 1.43, p = 0.02), as well as increased upper-body 1RM in older adults (1.56 kg, 95% CI 0.80 to 2.33, p = 0.01). However, MIP supplements were not superior when directly compared with protein-only (PRO) supplements.
Why it matters
This review shows that while adding ingredients to protein powders enhances resistance training gains over non-supplemented controls—particularly in older or untrained populations—multi-ingredient blends provide no demonstrated advantage over standard protein-only supplements.
Limits
The composition, specific ingredients, and dosages varied substantially across the 35 included trials (e.g., creatine vs. vitamin D), limiting conclusions about which specific added compounds provide efficacy. Additionally, the broader pooled effect was driven by comparisons against non-supplemented or placebo controls rather than active protein comparators.