Effects of high versus standard essential amino acid intakes on whole-body protein turnover and mixed muscle protein synthesis during energy deficit: A randomized, crossover study.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 32768315 · doi:10.1016/j.clnu.2020.07.019
What was done
Nineteen young men (mean ± SD: 23 ± 5 years old; BMI 25.4 ± 2.7 kg/m²) completed a randomized, double-blind crossover study involving two 5-day energy deficit periods (-30 ± 4% of total energy requirements) separated by a 14-day washout. Following each deficit, mixed muscle protein synthesis (MPS) and whole-body protein synthesis (PS), breakdown (PB), and net balance (NET) were measured at rest and post-resistance exercise using primed, constant L-[2H5]-phenylalanine and L-[2H2]-tyrosine infusions. Post-exercise, participants ingested either a standard (0.1 g/kg; 7.87 ± 0.87 g) or high (0.3 g/kg; 23.5 ± 2.54 g) essential amino acid (EAA) beverage.
What was found
Postabsorptive mixed MPS (%/h) at rest did not differ between conditions (P = 0.67). Postprandial mixed MPS increased above postabsorptive rest at both rest (standard EAA: 0.055 ± 0.01; high EAA: 0.061 ± 0.02; P = 0.02) and post-exercise (standard EAA: 0.055 ± 0.01; high EAA: 0.065 ± 0.02; P = 0.01), with no significant difference between EAA doses. For whole-body turnover (g/180 min), the change from postabsorptive baseline was significantly greater for high versus standard EAA for PS (mean difference: 3.4, 95% CI: 2.3 to 4.4; P = 0.001), PB suppression (-15.6, 95% CI: -17.8 to -13.5; P = 0.001), and NET balance (19.0, 95% CI: 17.3 to 20.7; P = 0.001). Circulating EAA concentrations were significantly higher with the high dose (P = 0.001).
Why it matters
During short-term caloric restriction, consuming high doses of EAAs does not augment muscle protein synthesis beyond standard levels, but it substantially improves whole-body net protein balance primarily by suppressing whole-body protein breakdown.
Limits
The sample was small (n = 19) and restricted to young, healthy males, limiting generalizability to females, older individuals, or clinical populations. The energy deficit was acute (5 days), so long-term effects on lean body mass preservation remain unmeasured.
Cited by
- partial A 30% caloric deficit in young, healthy adults increases the required amount of essential amino acids needed to maintain net protein balance by 300%.