Glycine is an amino acid, one of the fundamental molecules that form proteins. The body synthesizes glycine on its own, classifying it as a non-essential amino acid because it does not need to be obtained from the diet. Its structure is the simplest of all amino acids, a trait that allows it to fit into diverse biological roles.
Glycine’s Roles in the Body
Glycine is a primary component of collagen, the most abundant protein in mammals. Collagen forms the structural framework for skin, bones, tendons, and ligaments. Approximately every third position in the collagen triple helix is occupied by a glycine molecule, and this regular presence gives collagen its unique strength and flexibility.
Within the central nervous system, glycine performs a dual function. In the spinal cord and brainstem, it acts as an inhibitory neurotransmitter, helping to regulate motor and sensory information. Conversely, in the brain, it functions as a co-agonist at N-methyl-D-aspartate (NMDA) receptors, which are involved in learning and memory.
The body also uses glycine as a building block for other important compounds. It is a direct precursor to creatine, a substance that supplies rapid energy to muscle and nerve cells. Furthermore, glycine is one of the three amino acids required for the synthesis of glutathione, a significant antioxidant that helps protect cells from damage caused by free radicals.
Potential Health Benefits of Glycine Supplementation
Research suggests that taking glycine as a supplement may improve sleep quality. Consuming 3 grams of glycine before bedtime can lead to better self-reported sleep satisfaction, likely by helping to lower the core body temperature. Unlike some sleep aids, it does not typically cause feelings of drowsiness the following day.
Supplementation may also offer support for cognitive functions. Because of its role with NMDA receptors, glycine is involved in processes related to memory and mental performance. Some studies have investigated its potential to enhance memory, although more research is needed to fully understand this connection.
Given its role in collagen formation, additional glycine intake may support joint and bone health. By providing more of a building block for collagen, supplementation could help the body maintain and repair connective tissues. This is particularly relevant for the cartilage that cushions joints and for maintaining bone density over time.
Emerging science indicates a potential role for glycine in managing blood sugar. Glycine may enhance the body’s response to insulin, the hormone that regulates glucose levels. Research in individuals with type 2 diabetes has suggested that glycine might help improve blood sugar control by influencing a gut hormone that assists insulin’s function.
Dietary Sources and Supplementation
Glycine is naturally present in a variety of protein-rich foods, including meat, fish, poultry, eggs, and dairy products. Certain sources are exceptionally concentrated in this amino acid due to their high collagen content. These include the connective tissues in meats, bone broth, gelatin, pork skin, and chicken skin.
For those looking to increase their intake beyond diet, glycine is widely available as a supplement in powder or capsule form. The powder form is often preferred for its ease of mixing into liquids and for flexible dosing, while capsules offer convenience. People may supplement to obtain a targeted dose for specific health goals like sleep support.
Safety and Recommended Dosage
The U.S. Food and Drug Administration (FDA) has designated glycine as Generally Recognized as Safe (GRAS) for consumption. It is well-tolerated by most healthy adults when taken orally. There is no official recommended daily allowance for glycine, and dosages used in studies often range from 3 to 5 grams for sleep support.
Side effects from glycine supplementation are uncommon and generally mild. When they do occur, they most often involve gastrointestinal upset, such as nausea or soft stools, particularly at higher doses. People on antipsychotic drugs like clozapine should consult a healthcare provider before using glycine supplements, as interactions can occur.