Glycine

What is glycine?

Glycine is a conditionally essential amino acid, which can be produced in your body from other amino acids, but in certain circumstances, such as young age or heavy illness, you may need to obtain additional amounts from food to be healthy ^[1].

Glycine abbreviation (symbol): Gly

Glycine Functions in the Human Body

Glycine is ^[2,13]:

• A building block of proteins
• An inhibitory neurotransmitter
• A glucogenic amino acid — it can be converted into glucose
• A precursor of hemoglobin

Foods High in Glycine

• ANIMAL FOODS: meat, fish, cheese ^[4]
• PLANT FOODS: legumes ^[4]

Foods low in glycine: fruits, vegetables ^[4]

Glycine as a Food Additive

Glycine obtained from animal gelatin may be added to certain foods as a bread enhancer. It can be produced from animal gelatin or artificially synthesized ^[3]. In the European Union it is labeled as the E-number E640.

Glycine Supplements

Nonprescription (over-the-counter) L-glycine supplements are available as capsules or creams.

Glycine Health Benefits

L-glycine supplements are POSSIBLY EFFECTIVE in:

• Treatment of diabetic leg ulcers (when used as a arginine-aspartic acid-glycine cream) ^[5,11]
• Reducing complications of ischemic stroke ^[5,12]
• Improvement of symptoms of the hereditary metabolic disorder isovaleric acidemia ^[14]

There is INSUFFICIENT EVIDENCE about the effectiveness of glycine supplements in prevention or treatment of arthritis, benign prostatic hypertrophy, cancer, acute diarrhea in infants (when added to oral rehydration solution) ^[8,9], gastric ulcers, inflammation ^[7], phosphoglycerate dehydrogenase (3-PGDH) deficiency ^[6] or schizophrenia ^[10], or in improving memory, immunity or wound healing ^[5].

L-glycine supplements are PROBABLY INEFFECTIVE in the treatment of propionic acidemia ^[14] or in improving exercise performance ^[15].

Glycine Safety: Side Effects, Toxicity

Glycine seems to be SAFE for most people when taken by mouth or applied to the skin ^[5].

Side effects of oral l-glycine supplements may include nausea, stomach upset, vomiting and drowsiness ^[5].

Pregnant and breastfeeding women should avoid glycine supplements ^[5].

Glycine-Drug Interactions

Glycine supplements might decrease the effectiveness of clozapine (a drug to treat schizophrenia) ^[5].

Nonketotic Hyperglycinemia (Glycine Encephalopathy)

Nonketotic hyperglycinemia (glycine encephalopathy) is a hereditary disorder in which a lack of glycine cleavage enzyme result in a build up of glycine in the blood, urine and brain ^[16].

Symptoms develop shortly after birth and include feeding difficulties, vomiting, small head size, seizures, low or high muscle tonus and severe mental retardation ^[16].

Treatment includes a low-protein diet, sodium benzoate, arginine and dextromethorphane ^[16]. Most of the affected infants die within a year ^[16].