What Is L-Threonine?
L-Threonine is one of nine essential amino acids — the body cannot synthesize it. It is a unique amino acid because it is one of two (along with lysine) that are purely ketogenic and glucogenic. Threonine is necessary for the production of immunoglobulins (antibodies), so it is critically important for the immune system. In addition, threonine is a major component of mucins — protective proteins lining the digestive tract. It is also necessary for the structure of collagen and elastin, so it is important for joint, skin, and blood vessel health. For athletes, threonine is especially important due to immune protection during intense training and connective tissue maintenance.
L-Threonine Classification and Molecular Properties
| Property | Value |
|---|---|
| Type | Essential amino acid (polar, hydrophilic) |
| Molecular formula | C4H9NO3 |
| Molecular mass | 119.12 g/mol |
| Codons | ACU, ACC, ACA, ACG |
| Side chain | Hydroxyethyl group with -OH (polar) |
| Water solubility | Very good (97 g/L at 20°C) |
| RDA / Sports dose | 15 mg/kg (1.0 g/day) |
L-Threonine Benefits for Athletes
Immunoglobulin Production
Threonine is one of the main components of immunoglobulins (antibodies). Sufficient amounts are necessary for a strong immune system, especially for athletes after intense training.
Collagen and Elastin Synthesis
Threonine is necessary for the structure of collagen and elastin. It helps maintain the elasticity and strength of joints, tendons, skin, and blood vessels.
Gut Barrier Protection
Threonine is a major component of mucins — protective mucus lining the intestinal epithelium. It protects against “leaky gut” syndrome.
Liver Function
Threonine participates in the synthesis of glycine and serine in the liver. It also helps regulate fat metabolism in the liver and protects against steatosis.
Nervous System Support
Threonine is needed for neurotransmitter production. It participates in the synthesis of glycine — an inhibitory neurotransmitter — which helps with relaxation.
Muscle Recovery
As an essential amino acid, threonine is necessary for muscle protein synthesis after training. Its deficiency may slow recovery.
Dosage Recommendations
- Daily requirement: 15 mg/kg (1 g/day for an adult)
- Sports dose: 1–2 g per day with food
- To support immunity: 500–1000 mg twice per day
- For gut health: 1–2 g per day, divided into 2–3 doses
- Maximum safe dose: 4 g per day
Scientific Research
Immune Support
Athletes taking threonine (1 g/day) during intense training had 30% fewer upper respiratory tract infections.
Gut Barrier
Threonine supplements improved gut barrier function and reduced the amount of LPS (bacterial endotoxin) in the blood after long endurance training.
Collagen Synthesis
Threonine, together with proline and lysine, is necessary for collagen structure. Their combination increased collagen synthesis in an in vitro study.
Fat Metabolism in the Liver
Long-term threonine use (1 g/day for 3 months) reduced liver fat content by 15% in people with non-alcoholic fatty liver disease.
Practical Tips
Combine with Lysine and Proline
Threonine + lysine + proline are the main collagen components. Together they strengthen joints, skin, and tendons.
After Training with Carbohydrates
Threonine absorption is improved when taken with carbohydrates after training. This also helps the immune system.
For Gut Health
Threonine + glutamine is an excellent combination for strengthening the gut barrier. Both are necessary energy sources for enterocytes (intestinal cells).
For Vegetarians and Vegans
Threonine content in plant proteins is lower. Vegan athletes should consider threonine supplements.
L-Threonine Synergy with Other Supplements
- Threonine + Lysine + Proline: The main collagen synthesis trio. Together they strengthen joints, tendons, and skin — an ideal combination after injuries.
- Threonine + Glutamine: Both nourish intestinal cells and strengthen the gut barrier. An excellent combination for athletes with digestive issues.
- Threonine + Glycine: Threonine is a glycine precursor. Together they support liver detoxification and nervous system calming.
- Threonine + Vitamin C: Vit. C is an essential cofactor for collagen synthesis. The combination with threonine maximally stimulates collagen production.
Natural L-Threonine Sources in Food
| Food Product (100 g) | L-Threonine Amount | Extra Benefit |
|---|---|---|
| Egg whites | ~600 mg/100g | Complete protein, choline |
| Beef | ~900 mg/100g | Iron, B12, creatine |
| Chicken | ~850 mg/100g | Easily absorbed proteins |
| Fish | ~800 mg/100g | Omega-3, vitamin D |
| Soy products | ~700 mg/100g | Plant Proteins |
| Dairy products | ~500 mg/100g | Calcium, probiotics |
Animal proteins are the main sources of threonine. Vegans are recommended to choose soy products, lentils, and sesame seeds, which contain more threonine than other plant sources.
Who Needs L-Threonine Supplements the Most?
- Athletes During Intense Training: Threonine helps maintain immunity when the training load is highest.
- Athletes with joint problems: Threonine is essential for collagen - the main protein of joints and tendons.
- Athletes with digestive problems: Threonine strengthens the intestinal barrier through mucin production.
- Vegan Athletes: Risk of threonine deficiency due to lower content in plant proteins.
L-Threonine Deficiency Signs
Frequent Infections
Colds, upper respiratory tract infections after intense training - impaired immunoglobulin production.
Joint Pain
Decreased collagen production due to threonine deficiency can manifest as joint discomfort.
Digestive Problems
Loose stools, food intolerance - associated with insufficient mucin production.
Skin Problems
Dry, inelastic skin - threonine is essential for the structure of collagen and elastin.