Objective: To investigate whether supplementation with branched-chain amino acids (BCAAs) in patients with severe traumatic brain injury (TBI) improves recovery of cognition and influences plasma concentrations of tyrosine and tryptophan, which are precursors of, respectively, catecholamine and serotonin neurotransmitters in the brain.
Design: Forty patients with TBI were randomly assigned to 15 days of intravenous BCAA supplementation (19.6g/d) (n=20) or an isonitrogenous placebo (n=20).
Setting: Tertiary care rehabilitation setting in Italy.
Participants: Forty men (mean age, 32+/-15 y) with TBI and 20 healthy subjects (controls) matched for age, sex, and sedentary lifestyle.
Intervention: Supplementation with BCAAs.
Main outcome measures: Disability Rating Scale (DRS) and plasma concentrations of BCAAs, tyrosine, and tryptophan.
Results: Fifteen days after admission to the rehabilitation department, the DRS score had improved significantly in both the placebo group (P<.05 vs baseline) and in the BCAA-supplemented group (P<.01 vs baseline). The difference between the 2 groups was significant (P<.004). Plasma tyrosine concentration improved in the group given BCAA supplementation, and tryptophan concentration increased in patients receiving placebo.
Conclusions: Supplemental BCAAs enhance the retrieval of DRS without causing negative effects on tyrosine and tryptophan concentration.