glycine

Glycine is the smallest amino acid and one of the building blocks the body uses to make proteins. The MedlinePlus Medical Encyclopedia (National Library of Medicine, NIH) lists it among the "nonessential" amino acids, meaning the body can normally produce it on its own, and also lists it as "conditionally essential," meaning the need for it may increase during illness or stress. Glycine is also sold as a standalone dietary supplement, typically as a powder or capsule.

Rigorous evidence from US government health authorities is limited. The NIH Office of Dietary Supplements (ODS) and the National Center for Complementary and Integrative Health (NCCIH) do not publish a dedicated consumer fact sheet evaluating glycine as a supplement, and the MedlinePlus encyclopedia describes glycine only as a normal dietary amino acid rather than assessing any supplement claims. Because no authoritative federal consumer review establishes specific benefits, any claim that glycine treats, cures, prevents, or improves a health condition should be treated as unproven.

There is no government-established recommended supplement dose for glycine, since the body normally makes its own and it is also obtained from protein-containing foods. Amounts used in commercial products and in studies vary widely, so do not assume that more is better. Talk to your doctor, pharmacist, or another qualified clinician before starting glycine, especially if you are pregnant or breastfeeding, have a medical condition, or take prescription medicines.

Glycine occurs naturally in the diet and in the body, but the federal sources reviewed here do not provide a formal safety assessment of glycine taken as a concentrated supplement, so its long-term safety at supplement doses is not well characterized by these authorities. People who are pregnant or breastfeeding, who have kidney or liver conditions, or who take prescription medicines should be especially cautious and consult a clinician first. Dietary supplements are not reviewed by the FDA for safety and effectiveness the way prescription medicines are.

The government sources reviewed here do not catalog specific side effects of glycine supplements, so no authoritative federal side-effect profile is available. As with many supplements, taking concentrated amounts could in principle cause mild digestive upset in some people, though this is a general caution rather than a documented federal finding. Stop use and seek medical advice if you have an unexpected reaction.

No drug or supplement interactions for glycine are documented in the US government sources reviewed here, which does not mean none exist. To be safe, tell your doctor or pharmacist about all medicines and supplements you take so they can check for possible interactions before you add glycine.