Glycine
Also known as: Glycin, Glycine, Aminoacetic acid
The cheapest thing on this list with a real sleep effect — it lowers core body temperature, which is what actually initiates sleep.
Substance family
Vitamins, minerals, amino acids and enzymes. The recurring pattern: correcting an actual deficiency helps, supplementing beyond a normal level generally does not.
Effects on
Which outcomes this substance acts on — descriptive, not a recommendation.
Strain profile
Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.
This substance works against
Dosing & protocols by goal
Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.
Sleep quality
BasicDose
3000 mg
Frequency
30–60 min before bed
Cycle length
Ongoing
3 g is the dose used in the sleep trials. It dissolves easily and tastes sweet, so a powder is both cheaper and more practical than capsules at this amount.
Collagen and connective tissue support
BasicDose
5000–10000 mg / day
Frequency
Split, or alongside collagen
Cycle length
Ongoing
Glycine makes up roughly a third of collagen. A typical diet is comparatively low in it, since it sits in connective tissue rather than muscle meat.
Glutathione support
BasicDose
3000–5000 mg / day
Frequency
Split into 2 doses
Cycle length
Ongoing
Glycine and cysteine are the two limiting building blocks of glutathione — the reason it is often combined with NAC.
Side effect & countermeasure
Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.
Problem
Expecting sedation
Countermeasure
Glycine does not knock anyone out. It lowers core body temperature and shortens the time to fall asleep, and the effect people report is waking up less tired rather than falling asleep faster. Judging it by how sleepy it makes you miss the point.
Problem
Capsules at this dose are impractical
Countermeasure
3 g in 500 mg capsules is six capsules. The powder costs a fraction, dissolves clear and tastes sweet — one of the few supplements where the powder is straightforwardly better.
Problem
Sedation stacking
Countermeasure
Combined with ashwagandha, melatonin or alcohol the effects add up. Mild, but relevant if early alertness is needed.
Problem
Digestive upset at high doses
Countermeasure
Above roughly 10 g, loose stools and nausea are common. Splitting the dose resolves it; there is no reason to go that high for sleep.
Overview
Glycine is the smallest amino acid and one of the least glamorous supplements available. It is also, per euro, probably the most useful thing on this list for someone whose sleep is poor.
Mechanism of Action
Two things happen. Glycine acts as an inhibitory neurotransmitter in the central nervous system — the same broad category as GABA — which contributes a mild calming effect.
More interesting is the temperature effect. Falling asleep requires core body temperature to drop; that drop is the physiological trigger, which is why a warm room or a late hard session makes sleep difficult. Glycine promotes peripheral vasodilation, so heat is released through hands and feet and core temperature falls faster.
That is why it works without sedating. It does not force sleep — it removes an obstacle to it.
Where It Fits Here
Sleep quality. The trials are small but consistent: shorter time to fall asleep, better subjective sleep quality, and less fatigue the following day. Notably, participants did not report feeling drugged, which distinguishes it from most sleep aids.
Connective tissue. Roughly a third of collagen is glycine. Anyone training heavily, and particularly anyone on compounds that stiffen connective tissue while strength rises quickly, has a reason to care about collagen supply. A typical high-protein diet built on muscle meat is comparatively low in glycine, because glycine is concentrated in the parts most people do not eat.
Glutathione. The body's main endogenous antioxidant is built from glycine, cysteine and glutamate. Cysteine is usually the limiting factor — that is NAC's role — but glycine becomes limiting too as people age. The combination has better evidence than either alone.
Realistic Expectations
This is not a compound that will be noticed dramatically. What people typically report after a few weeks is waking up feeling like they actually slept.
That is worth more than it sounds. Sleep is where the recovery from training and the hormonal repair actually happens, and it is the variable most often sacrificed in a hard prep. Nothing else on this list of supplements produces a comparable effect for the price.
Side Effects & Risks
- Very well tolerated
- Loose stools or nausea above roughly 10 g
- Mild additive sedation with other sleep aids
- Caution alongside clozapine, where it can reduce efficacy
Blood Work & Monitoring
- No routine monitoring required
- If sleep remains poor despite this, look at stimulant timing, cortisol and blood pressure rather than at the next supplement
Legal status by region
Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.
| Region | Regulatory status |
|---|---|
| United States | Dietary supplement |
| EU / UK | Food supplement |
| Most other jurisdictions | Freely available |
| Competitive sport | Not prohibited |