Glycine
Also known as L-glycine
Glycine is the smallest amino acid and conditionally essential, meaning the body makes it but may not make enough during growth or high demand. It makes up about a third of collagen and helps build creatine and the antioxidant glutathione.
Why it matters
What it does in your body
- Major component of collagen
- Building block of creatine and glutathione
- Calming neurotransmitter in the spinal cord and brain
- Part of bile acids for fat digestion
Intake guidance
How much you need
There is no formal daily requirement, but research suggests the body may not always make as much glycine as it can use, so it is considered conditionally essential. Collagen-rich foods and dietary protein supply it, and typical synthesis plus diet covers most needs.
What affects it
What affects your intake
Collagen and connective tissue demand
Because glycine is a third of collagen, needs rise when the body is building or repairing connective tissue.
Diet source
Bone broth, gelatin, and skin-on meats are far richer in glycine than muscle meat alone.
Body's own production
The body synthesizes glycine, but some evidence suggests output may fall short of full metabolic demand.
In practice
Good to know
Good to know: glycine is widely sold as a sleep and relaxation supplement, and a few grams before bed may modestly improve sleep quality in some people. It is also the reason bone broth and collagen supplements are rich in this amino acid. It is inexpensive, tastes slightly sweet, and has a good safety record at typical doses.
Where to get it
Best food sources
The bottom line
Glycine builds collagen and calms the nervous system, and collagen-rich foods top it up. It is a popular, low-risk sleep supplement with modest evidence.
Track glycine automatically
Glycine is one of the 92 nutrients Vora reads from a photo of your meal, so you can see where you stand without weighing or logging by hand.
Sources and method
The classification, roles, and guidance on this page come from the references below, drawing on the Institute of Medicine (now the National Academies) Dietary Reference Intakes and reputable nutrition science.
- Institute of Medicine (2005), Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
- National Library of Medicine, MedlinePlus
This page is for general education, not medical advice. Reference intakes are population averages for healthy people and do not replace guidance from your doctor or a registered dietitian, especially if you are pregnant, managing a health condition, or considering supplements.