Get Your Personalized Supplement StackSupplement Stack Quiz

GLICINA

Also known as: Glycine, Aminoacetic acid, Amino acid, C₂H₅NO₂

Overview

Glycine is a non-essential amino acid synthesized by the human body and found in protein-rich foods like meat and collagen. It serves as a building block for proteins and participates in various physiological processes. As a supplement, glycine is used for its potential benefits, including improving exercise performance, metabolic health, and neurological function. It is available in powder or capsule form and is often included in collagen supplements. Research on glycine supplementation is emerging, with some promising findings, but is still limited by the number of large, high-quality randomized controlled trials (RCTs). Systematic reviews on amino acid supplementation often include glycine but rarely isolate its effects exclusively. Overall, the evidence base is moderate, with a need for more targeted RCTs specifically on glycine.

Benefits

Glycine supplementation may offer several benefits. Some evidence suggests it can enhance peak power output and reduce lactic acid accumulation during high-intensity exercise, potentially improving exercise capacity. Systematic reviews of protein and essential amino acid (EAA) supplementation, including glycine, in older adults indicate improvements in fat-free mass, muscle strength, and physical function. Glycine may also improve insulin response and help manage or prevent diabetes in at-risk populations by influencing glucose metabolism. Additionally, glycine has potential anti-inflammatory properties, although direct high-quality evidence is limited. Effect sizes vary by study and population, but meta-analyses on amino acid supplementation generally report small to moderate improvements in muscle-related outcomes in older adults. The time course for benefits ranges from weeks to months depending on the endpoint.

How it works

Glycine acts as an inhibitory neurotransmitter in the central nervous system and modulates NMDA receptor activity, which may underlie some neurological benefits. It participates in the synthesis of proteins, glutathione (an antioxidant), and other metabolites critical for cellular function. Glycine may improve exercise performance by buffering lactic acid and supporting energy metabolism during high-intensity activity. It also influences insulin secretion and glucose metabolism, potentially improving metabolic control. Glycine is absorbed efficiently from the gut, especially when consumed as part of collagen peptides, which may enhance bioavailability.

Side effects

Glycine is generally recognized as safe when consumed in typical supplemental doses (2-5 grams daily). Common side effects are rare and mild, including gastrointestinal discomfort in some individuals. There are no widely reported serious adverse effects or contraindications in healthy populations. Potential interactions with medications exist, particularly those affecting glucose metabolism; consultation with a healthcare provider is advised before supplementation. Special populations such as pregnant women or those with severe kidney disease should use caution due to limited data. It is important to adhere to recommended dosages to minimize the risk of adverse effects.

Dosage

Typical supplemental doses of glycine range from 2 to 5 grams per day. Optimal dosing for specific benefits, such as exercise performance or metabolic health, is not firmly established but often falls within this range. Glycine is often taken in powder form mixed with water or included in collagen supplements. Absorption may be enhanced when glycine is consumed as part of collagen peptides rather than in free form. No specific cofactors are required for glycine absorption, but overall protein intake and nutritional status may influence outcomes. It's advisable to start with a lower dose and gradually increase it to assess tolerance.

FAQs

Is glycine supplementation safe?

Yes, at typical doses (2-5 g/day), glycine is generally considered safe for most people. However, individuals with pre-existing health conditions should consult with a healthcare provider before starting supplementation.

When should glycine be taken?

Timing is flexible; some take it before exercise for performance benefits or before bedtime for potential neurological effects. Experiment to find what works best for you.

How soon will benefits appear?

Improvements in muscle function or metabolic markers may take weeks to months of consistent supplementation. Be patient and track your progress.

Does glycine work better with other amino acids?

Glycine is often combined with other amino acids in collagen or protein supplements, which may enhance overall effects due to synergistic interactions.

Research Sources

https://www.mdpi.com/2075-4663/12/10/265 – This narrative review summarizes the effects of glycine supplementation on exercise performance. It suggests that glycine may enhance peak power output and reduce lactic acid during high-intensity exercise, indicating potential ergogenic benefits. However, the review notes the limited number of large RCTs and heterogeneity in study designs.
https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/systematic-review-and-metaanalysis-of-the-effect-of-protein-and-amino-acid-supplements-in-older-adults-with-acute-or-chronic-conditions/83C8288C73D79685854E78D5415B9029 – This systematic review and meta-analysis examined the effect of protein and essential amino acid supplementation, including glycine-containing supplements, in older adults. The findings indicate that protein/EAA supplementation improves fat-free mass, muscle strength, and physical function with small to moderate effect sizes. The authors note that glycine, as part of collagen, may contribute to these improvements.
https://journals.lww.com/ijnp/fulltext/2025/01000/systematic_review_of_branched_chain_amino_acid.1.aspx – This systematic review focuses on branched-chain amino acids and their role in modulating inflammation. While the review primarily discusses BCAAs, it suggests that glycine also has potential anti-inflammatory properties, although it has been less studied directly. The review highlights the broader role of amino acids in influencing inflammatory processes.
https://www.webmd.com/diet/health-benefits-glycine – This WebMD article provides a general overview of the health benefits of glycine. It discusses glycine's role in improving sleep quality, supporting cognitive function, and promoting wound healing. The article also mentions glycine's potential to help regulate blood sugar levels and reduce inflammation.