01 — The common model is incomplete

Melatonin is a timing signal, not a sleep trigger.

Most sleep products are built on the assumption that melatonin causes sleep. It doesn't. Melatonin is the body's circadian timing signal, it communicates darkness and helps set when the sleep window opens. That is a real and useful role, but it is a clock, not a switch.

Melatonin does not lower a hyperaroused state, quiet neural firing, or initiate the transition into slow-wave sleep. This is why people with normal melatonin rhythms, or those supplementing it, can still lie awake: the clock says "night," but the system never receives the separate signal that says "safe to descend."

02 — The actual trigger

Deep sleep is gated by core body temperature.

Human core temperature follows a circadian curve and falls in the evening. The descent into deep, slow-wave sleep is closely coupled to this fall: as the core cools by roughly half a degree Celsius (about 1°F), the brain receives the physiological cue to initiate and sustain deep sleep.

The body achieves this drop through distal vasodilation, widening the blood vessels in the hands and feet to shed heat from the core to the surface. Greater heat loss at the periphery means a faster, deeper core-temperature decline, and a stronger sleep-onset signal.

03 — Why an exhausted person stays awake

Hyperarousal blocks the signal from two directions.

A nervous system running elevated cortisol and sympathetic tone, the "wired but tired" state, interferes with sleep onset in two distinct ways:

• Thermoregulatory: sympathetic activity restricts peripheral blood flow, blunting the distal vasodilation that drives the core-temperature drop. The cooling signal never fully arrives.
• Neural: excitatory firing keeps the brain in a monitoring, alert state. Without sufficient inhibitory tone to counter it, the system can't quiet enough to descend, even when sleep pressure is high.

Effective intervention has to address both: produce the temperature signal and strengthen the inhibitory braking. Most single-mechanism approaches address neither directly.

04 — The compound

Glycine acts on both pathways.

Glycine is a non-essential amino acid the body already produces and uses. In the context of sleep onset it has two relevant actions, which is what makes it unusual:

1. Thermoregulatory action

Glycine taken before bed promotes peripheral vasodilation, increasing blood flow to the hands and feet and accelerating the core-temperature drop, physically producing the cooling signal described above. Studies attribute this to action on receptors in the hypothalamus, the region governing both body temperature and the sleep-wake cycle.

2. Inhibitory neurotransmitter action

Glycine is also one of the central nervous system's primary inhibitory neurotransmitters. It dampens excitatory firing, the looping, monitoring, alert activity that keeps a hyperaroused brain running, supplying the braking the system was missing.

The result is signal plus inhibition: the body is cued to cool and descend, while the neural noise that was preventing descent is quieted. Not sedation. Not hormone replacement.

05 — What the research shows

The clinical findings on 3g glycine.

Human trials examining glycine before bed (commonly at a 3-gram dose) have reported the following. These are findings from the published literature on glycine and sleep; they describe the compound, not any specific product.

The mechanism proposed across this work is consistent: glycine lowers core body temperature via peripheral vasodilation, and the temperature drop is associated with the improvements in sleep onset and depth. The effect is described as facilitating the body's own sleep process, rather than sedating it.

06 — Dose matters

Why most products miss, even when they list glycine.

The clinical dose in the research is 3 grams. This is the single most common failure point in commercial formulas: glycine appears on the label, but at a fraction of the studied amount, often a few hundred milligrams folded into a proprietary "sleep blend." A sub-clinical dose will not reliably produce the thermoregulatory effect the studies describe.

When evaluating any glycine product, the question isn't "does it contain glycine?" It's "does it contain the clinical dose, stated plainly, not buried in a blend?"

07 — The formula we found

A product built to the clinical dose.

We went looking for a melatonin-free formula built around the full clinical dose rather than a token amount. SNUGZ was the one that matched the research.