Threonine is a harmless amino acid; clinical trials have demonstrated a modest reduction in spasticity that does not appear to be clinically significant.
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Description
Threonine is an essential neutral (aliphatic) amino acid.
Food Sources
Most protein-containing foods
Mechanism/Pharmacokinetics
- Threonine is a part of most proteins and is one precursor of glycine; administration of L-threonine increases glycine levels in rat spinal cord (1). Plasma half-life is 2 days (2).
[Outline]
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Clinical Trials
- Familial spastic paraparesis
- A double-blind, placebo-controlled crossover study in 18 patients with familial spastic paraparesis (FSP) tested the effects of L-threonine (4.5 or 6.0 g/day, each for 2 weeks). Outcome measures included physician global impression; patient global impression; and semiquantitative ratings of strength, muscle tone, deep tendon reflexes, walking, hopping, and running. There was a statistically significant decrease in motor impairment and spasticity; however, neither physician nor patient global impressions noted significant treatment effects (1).
- Spinal spasticity
- A double-blind, placebo-controlled, crossover study of oral L-threonine (6 g/day × 2 weeks, with a 2-week washout between phases) in 33 patients with spinal spasticity (29 completed) found a modest benefit of L-threonine over placebo (3). A sequential analysis was used (in which patients were enrolled until patient preferences reached significance at the 5% level); this level was reached for threonine after 33 patients were enrolled. As measured by the Ashworth scale, which assesses lower limb spasticity, 16 patients responded to threonine, 3 to placebo, 2 to both and 8 responded to neither. Symptomatic improvement was reported by six patients receiving threonine and two patients receiving placebo. One treated patient reported diarrhea, and one reported indigestion.
- Multiple sclerosis
- A randomized, placebo-controlled crossover trial tested threonine (7.5 g/day in divided doses) in 26 ambulatory patients with multiple sclerosis (21 completed both phases). Each phase lasted 8 weeks, and there was a 2-week washout between phases. Threonine significantly reduced signs of spasticity on clinical examination (Clinician Spasticity Scale); however, neither physician nor patient noted any symptomatic improvement. Neurophysiologic measures did not differ between phases. No side effects of threonine were seen (4).
- Amyotrophic lateral sclerosis
- A randomized year-long trial of 30 patients with amyotrophic lateral sclerosis compared L-threonine with vitamin B complex or carnitine. Only 13 patients (including 9 patients taking threonine and 4 controls) completed the trial. There were no significant differences between the threonine-treated group and the control participants in decreased clinical assessment scores (5). A randomized, double-blind, placebo-controlled trial of L-threonine (2 g daily) in 15 patients with amyotrophic lateral sclerosis found no significant differences between the two groups (6).
Other Claimed Benefits/Actions
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Recommended Dietary Allowance
Estimates of Dietary Amino Acid Requirements (7)
| Infants and Children |
| 3 to 4 months | 87 mg/kg/day |
| 2 to 5 years | 37 mg/kg/day |
| 10 to 12 years | 28 mg/kg/day |
| Adults | 7 to 15 mg/kg/day |