Glycine

What It Is

Glycine is the simplest amino acid, chemically characterized by having a single hydrogen atom as its side chain. It is considered a non-essential amino acid, meaning the body can synthesize it from other compounds such as serine and choline, even if it’s not obtained directly from dietary sources. Despite being “non-essential,” glycine plays several essential roles in maintaining health and metabolic function.

It is found abundantly in collagen, the main structural protein in skin, connective tissue, and cartilage. Rich dietary sources include gelatin, bone broth, meat (especially skin and connective tissue), fish, dairy, and legumes.

How It Works

Glycine functions in multiple physiological systems:

1. Protein and Collagen Synthesis. Glycine is one of the three primary amino acids (along with proline and hydroxyproline) that make up collagen. Collagen production is critical for the strength, elasticity, and repair of tissues such as skin, tendons, ligaments, and bones.
2. Neurotransmitter Function. In the central nervous system, glycine acts as an inhibitory neurotransmitter, particularly in the spinal cord, brainstem, and retina. It helps regulate nerve impulses and promotes relaxation and sleep by tempering overexcitation in the nervous system. Glycine also modulates NMDA receptors, which are involved in learning, memory, and cognition.
3. Metabolic Support and Detoxification. Glycine contributes to the synthesis of important biomolecules such as glutathione, a major antioxidant that helps protect cells from oxidative stress. It is also involved in the conjugation of bile acids and detoxification of xenobiotics (foreign substances) in the liver.
4. Energy and Blood Sugar Regulation. By influencing gluconeogenesis (the creation of glucose from amino acids), glycine can help stabilize blood sugar levels and support energy metabolism.
5. Anti-Inflammatory and Cytoprotective Effects. Glycine has been shown in studies to reduce inflammatory signaling and improve tissue recovery after injury or oxidative stress, largely through its impact on immune modulation and antioxidant pathways.

Why It’s Important

Glycine is important for a variety of health reasons:

• Joint, Skin, and Connective Tissue Health: Because of its role in collagen synthesis, glycine supports joint flexibility, wound healing, and skin elasticity.
• Sleep and Cognitive Function: Supplementation may improve sleep quality and reduce daytime fatigue by calming the nervous system.
• Liver and Metabolic Health: Glycine supports detoxification and may help reduce fatty liver accumulation, particularly in metabolic disorders.
• Antioxidant Defense: As a component of glutathione, glycine contributes to protection against cellular damage and aging.
• Muscle Preservation: It aids in muscle repair and may reduce muscle wasting during illness or fasting.

Considerations

While glycine is generally well-tolerated and safe, a few considerations apply:

• Dosage: Common supplemental doses range from 1 to 5 grams daily, though some studies use up to 10 grams. Higher doses may cause mild gastrointestinal discomfort in sensitive individuals.
• Interactions: Glycine’s calming effects can potentiate the sedative properties of certain medications (such as sleep aids or antipsychotics), so concurrent use should be approached with caution.
• Underlying Conditions: Individuals with kidney or liver disease should consult a healthcare provider before supplementing, as amino acid metabolism can be affected in these conditions.
• Pregnancy and Breastfeeding: While glycine from food is safe, the safety of high-dose supplementation during pregnancy or lactation has not been fully established.
• Individual Needs: People with higher demands for collagen synthesis (e.g., athletes, those healing from injury, or older adults) may particularly benefit from additional glycine intake.