Glycine (Gly or G) is the simplest of the 20 amino acids. Its single hydrogen atom side chain makes it the smallest and most flexible. Though non-essential, as the body can synthesize it, glycine is significant for many bodily functions.
Glycine’s Fundamental Roles in the Body
Glycine is a building block for many proteins, especially collagen, the most abundant protein in humans. Collagen provides structural support to connective tissues like skin, bones, tendons, and cartilage. Glycine’s small size allows it to fit into collagen’s triple helix, stabilizing its structure.
Beyond protein synthesis, glycine is a precursor for other important molecules. It is one of three amino acids, with cysteine and glutamate, needed for glutathione synthesis, a powerful antioxidant protecting cells from damage. Glycine also produces creatine, which supports energy in muscles and the brain.
Glycine also functions as an inhibitory neurotransmitter, especially in the brainstem and spinal cord. It calms neuronal activity, regulating sleep and pain perception. Additionally, glycine contributes to heme synthesis, a hemoglobin component that transports oxygen in red blood cells.
Health Benefits of Glycine
Glycine’s role as an inhibitory neurotransmitter improves sleep quality by calming the nervous system. Studies show taking glycine before bed can shorten sleep onset, enhance sleep quality, and reduce daytime sleepiness.
Glycine’s involvement in glutathione synthesis supports liver detoxification and cellular protection. Glutathione helps the liver neutralize toxins, and glycine aids in their removal.
Glycine’s contribution to collagen formation supports skin health, elasticity, and joint and connective tissue maintenance. Adequate glycine levels benefit tissue repair and musculoskeletal health. It also supports muscle repair and growth, especially for athletes and during recovery.
Glycine can influence blood sugar regulation by enhancing insulin’s ability to remove glucose from the bloodstream. Research suggests glycine supplementation may improve insulin secretion, assisting in type 2 diabetes management or prevention. Its anti-inflammatory and antioxidant properties may also protect against cardiovascular damage and heart disease.
Sources of Glycine
Glycine can be obtained through various dietary sources, primarily protein-rich foods. Foods high in collagen, such as bone broth and gelatin, are excellent sources. For instance, a single ounce of gelatin can provide over 5 grams of glycine, while a cup of bone broth may offer around 1.7 grams.
Meats like poultry, beef, and pork contribute to glycine intake. Chicken skin, for example, contains approximately 3.3 grams per 3.5 ounces. Fish, particularly carp, catfish, and salmon, also provides glycine. Smaller amounts are found in plant-based sources such as legumes (e.g., soybeans, lentils, kidney beans), dairy products (milk, yogurt, cheese), and some vegetables like spinach and asparagus.
Glycine is available as a standalone dietary supplement. Supplementation can address dietary gaps or support specific health goals, such as improving sleep or joint health. Collagen supplements also increase glycine intake.
Safety and Considerations
Glycine is generally considered safe for most individuals at recommended dosages. Doses up to 6 grams daily for four weeks have been well-tolerated. As with any supplement, consult a healthcare professional before starting a new regimen.
While generally safe, high doses of glycine may rarely cause mild digestive upset, such as nausea, vomiting, or diarrhea. Drowsiness has also been reported. These side effects are usually mild and temporary.
Pregnant or nursing women are advised to avoid glycine supplements, as their safety has not been definitively established. Individuals with pre-existing medical conditions, especially liver disease, or those on medication, should seek medical advice before taking glycine, as it may interact with certain drugs like antipsychotics or blood pressure medications. Typical supplemental dosages for adults range from 3 to 5 grams per day for general health support or sleep improvement.