Nutraceuticals for traumatic brain injury: Should you recommend their use?

Vitamin D. An animal study reported that vitamin D supplementation can help reduce inflammation, oxidative stress, and cell death in TBI, and that vitamin D deficiency has been associated with increased inflammation and behavioral deficits.¹⁷ Further evidence suggests that vitamin D may have a synergistic effect when used in combination with the hormone progesterone. A RCT of 60 patients with severe TBI reported that 60% of those who received progesterone plus vitamin D had GOS scores of 4 (good recovery) or 5 (moderate disability) vs 45% receiving progesterone alone or 25% receiving placebo.¹⁸

Magnesium, one of the most widely used nutraceuticals, is considered essential for CNS functioning, including the regulation of N-methyl-d-aspartate receptors and calcium influx. After a TBI, magnesium deficiency can result in increased oxidative stress and cell death and has been associated with greater neurologic impairment. Animal studies have provided some evidence of the potential neuroprotective effects of magnesium, but human trials have found mixed evidence. One small human study reported a correlation between magnesium balance and oxidative stress in TBI patients.¹⁹

A RCT evaluated the safety and efficacy of magnesium supplementation in 60 patients with severe closed TBI, with one-half randomized to standard care and the other also receiving magnesium sulfate (MgSO₄; initiation dose of 4 g IV and 10 g IM, continuation dose of 5 g IM every 4 hours for 24 hours).²⁰ After 3 months, more patients in the MgSO₄ group had higher GOS scores than controls (73.3% vs 40%), lower 1-month mortality rates (13.3% vs 43.3%), and lower rates of intraoperative brain swelling (29.4% vs 73.3%).

However, a larger RCT of 499 patients with moderate or severe TBI randomized to high-dose (1.25 to 2.5 mmol/L) or low-dose (1.0 to 1.85 mmol/L) IV MgSO₄ or placebo provided conflicting results.²¹ Participants received MgSO₄ 8 hours after injury and continued for 5 days. After 6 months, patients in the high-dose MgSO₄ and placebo groups had similar composite primary outcome measures (eg, seizures, neuropsychological measures, functional status measures), although the high-dose group had a higher mortality rate than the placebo group. Patients who received low-dose MgSO₄ showed worse outcomes than those assigned to placebo.

Amino acids. Branched-chain amino acids (BCAAs), including valine, isoleucine, and leucine, are essential in protein and neuro­transmitter synthesis. Reduced levels of endogenous BCAAs have been reported in patients with mild or severe TBI.²² Preclinical studies suggest that BCAAs can improve hippocampal-dependent cognitive functioning following TBI.²³

Two RCTs of BCAAs have been conducted in humans. One study randomized 40 men with severe TBI to IV BCAAs or placebo.²⁴ After 15 days, the BCAA group showed greater improvement in Disability Rating Scale scores. The study also found that supplementation increased total BCAA levels without negatively affecting plasma levels of neurotransmitter precursors tyrosine and tryptophan. A second study found that 41 patients in a vegetative or minimally conscious state who received BCAA supplementation for 15 days had higher Disability Rating Scale scores than those receiving placebo.²⁵

Probiotics and glutamine. Probiotics are non-pathogenic microorganisms that have been shown to modulate the host’s immune system.²⁶ TBI is associated with immunological changes, including a shift from T-helper type 1 (TH1) cells to T-helper type 2 (TH2) cells that increase susceptibility to infection.²⁷

A RCT of 52 patients with severe TBI suggested a correlation between probiotic administration-modulated cytokine levels and TH1/TH2 balance.²⁸ A 3-times daily probiotic mix of Bifidobacterium longum, Lactobacillus bulgaricus, and Streptococcus thermophilus for 21 days led to shorter average ICU stays (6.8 vs 10.7 days, P = .034) and a decrease in nosocomial infections (34.6% vs 57.7%, P = .095) vs placebo, although the latter difference was not statistically significant.²⁸

A prospective RCT of 20 patients with brain injury²⁹ found a similar impact of early enteral nutrition supplemented with Lactobacillus johnsonii and glutamine, 30 g, vs a standard enteral nutrition formula. The treatment group experienced fewer nosocomial infections (50% vs 100%, P = .03), shorter ICU stays (10 vs 22 days, P < .01), and fewer days on mechanical ventilation (7 vs 14, P = .04). Despite these studies, evidence for the use of glutamine in patients with TBI is scarce and inconclusive.

N-acetylcysteine (NAC) comes from the amino acid L-cysteine. NAC is an effective scavenger of free radicals and improves cerebral microcirculatory blood flow and tissue oxygenation.³⁰ A randomized, double-blind, placebo-controlled study of oral NAC supplementation in 81 active duty service members with mild TBI found NAC had a significant effect on outcomes.³¹ Oral NAC supplementation led to improved neuropsychological test results, number of mild TBI symptoms, complete symptom resolution by day 7 of treatment compared with placebo, and NAC was well tolerated. Lack of replication studies and generalizability of findings to civilian, moderate, or chronic TBI populations are key limitations of this study.

Proposed mechanisms for the neuro­protective benefit of NAC include its antioxidant and inflammatory activation of cysteine/glutamate exchange, metabotropic glutamate receptor modulation, and glutathione synthesis.³² NAC has poor blood–brain permeability, but the vascular disruption seen in acute TBI might facilitate its delivery to affected neural sites.³¹ As such, the benefits of NAC in subacute or chronic TBI are questionable.