Benefits
Collagen and Elastin Synthesis
L-Threonine is a building block for collagen (along with glycine, proline, hydroxyproline) and elastin. Important for skin, connective tissue, joint, and tendon health. Whole-protein collagen sources are more efficient than isolated threonine for these effects.
Mucin / Gut Mucosal Layer
L-Threonine is a major component of mucin glycoproteins — the protective mucosal layer lining the GI tract. Animal studies suggest threonine is rate-limiting for mucin synthesis; clinical relevance to humans not established.
Immune Function
L-Threonine contributes to immunoglobulin synthesis. Deficiency impairs antibody production; rare in protein-adequate diets.
Hereditary Spastic Paraparesis (Limited)
Older small trials examined L-threonine for hereditary spastic paraparesis with mixed signals. Mechanism proposed via glycine pathway. Not standard care; modern HSP management remains primarily supportive.
ALS Adjunct (Investigational)
Theoretical glycine receptor modulation has prompted exploratory use in amyotrophic lateral sclerosis. Evidence remains preliminary.
Mechanism of action
Protein Synthesis
Essential amino acid required for ribosomal protein synthesis. Hydroxyl side chain provides O-glycosylation sites in mucins and other glycoproteins.
Glycine Pathway
L-Threonine can be metabolized to glycine via threonine dehydrogenase + serine hydroxymethyltransferase. Theoretical basis for some neurological applications via inhibitory glycine receptors.
Mucin Synthesis
Threonine is heavily represented in mucin protein backbones (alongside serine and proline) — the heavily-glycosylated proteins forming the protective mucosal layer in the GI tract and respiratory tract.
Lipotropic Effects
Threonine prevents fat accumulation in the liver — works alongside choline, methionine, and inositol as a lipotropic factor. Animal studies more robust than human evidence.
Clinical trials
Small RCT of L-threonine supplementation (7.5 g/day) in patients with hereditary spastic paraparesis. (Growdon et al. 1991, Neurology — or similar)
Small HSP patient group.
Modest signals on spasticity in some patients; not consistently replicated. Older trial; not standard care. Modern HSP management primarily supportive (PT, baclofen, tizanidine).