Glycine

The verdict

Is Glycine worth taking?

Glycine is the most abundant amino acid in collagen and one of the most underconsumed in modern diets that favor lean muscle meat over connective tissue cuts. Three grams before bed is one of the most effective and best-tolerated sleep interventions available. Five to ten grams during the day supports collagen synthesis, particularly when taken with vitamin C before exercise. Bone broth, gelatin, and skin-on animal foods cover glycine well from food. If you are not eating these regularly, supplementation is practical and extremely safe.

What it does

What Glycine does in the body

Sleep quality, collagen synthesis, muscle recovery, anti-inflammatory activity, and gut integrity. Glycine is the simplest amino acid and one of the most biologically versatile. It makes up approximately one-third of all amino acids in collagen, making it rate-limiting for connective tissue repair when demand is high. Research suggests most adults running a consistent training load have a glycine deficit of 10 g or more per day relative to what collagen synthesis and metabolic function demand, because the body produces only 3 g daily and diet provides 2 to 3 g from typical food sources. Beyond structural repair, glycine acts as an inhibitory neurotransmitter that lowers core body temperature before sleep, one of the key physiological signals that drives sleep onset. It also reduces pro-inflammatory cytokines including TNF-alpha and supports gut barrier integrity through its role in glutathione synthesis alongside cysteine and glutamine.

The evidence

What the research actually shows

Strong. Sleep quality improvement at 3 g before bed is consistently demonstrated across multiple trials. Collagen synthesis support is mechanistically well established and supported by intervention studies using glycine-rich gelatin and collagen peptides. Anti-inflammatory activity and gut integrity support are well characterized in clinical and mechanistic research. A 2024 review in Sports confirmed glycine’s safety profile and anti-inflammatory mechanisms. It is well tolerated at all supplemental doses with no meaningful safety concerns.

Food first

Getting Glycine from food

Bone broth, gelatin, chicken skin, oxtail, pork belly, and slow-cooked connective tissue cuts are the richest food sources. Traditional whole-animal cooking covers glycine well. The modern preference for lean boneless cuts at the expense of skin, bone, and collagen-rich tissue is the primary driver of glycine inadequacy in active adults eating otherwise clean diets.

From the kitchen

A chef's note on Glycine

I make bone broth weekly. A quality broth simmered for 12 or more hours from grass-fed bones and feet is one of the most glycine-dense foods available and one of the simplest ways to cover connective tissue nutrition from the kitchen. My clients who switch to regular bone broth consumption notice improvements in joint comfort and skin quality within a few weeks. The supplement is excellent but the food version is something I genuinely prefer cooking with.

What the guide adds

The part that is not on this page

Everything above is the assessment. What the guide adds for Glycine is the protocol:

• Optimal Form
• Bioavailability
• Purity Red Flags
• Stack With / Avoid

147 entries across nine categories, every one graded against the clinical literature the same way.

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About the author

Who graded this

Daniel Edlund is a Le Cordon Bleu-trained private chef in Los Angeles, a certified personal trainer and strength coach, and an internationally licensed massage therapist. Thirty years of strength training and fifteen years cooking in private estate kitchens. He is the author of The Complete Supplement Guide, which grades 147 entries against the clinical literature, and of The EASY Way to Organic Cooking, first published in 2013.

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This page is information, not medical advice. Supplements interact with prescription medication and with each other, and the right answer depends on your own bloodwork and history. Talk to your doctor before starting anything, particularly if you are pregnant, nursing, managing a health condition, or already taking medication.

Also in Recovery & Joint Health

Related entries

• Collagen Peptides (Type I / Type II / UC-II) — Strong evidence
• Curcumin / Turmeric — Moderate evidence
• Tart Cherry Extract (Montmorency) — Strong evidence
• L-Glutamine — Moderate evidence

All 147 entries, graded →