Walk down any "sleep aid" aisle and 80% of the bottles have melatonin in them. It's the default. The thing you reach for when you can't sleep.
It's also the thing we deliberately left out of Moon Milk.
This isn't an anti-melatonin rant. Melatonin has real, narrow uses — short-term jet lag, shift-work transitions, certain circadian disorders. But the way the supplement industry uses it, and the way most people take it night after night, is a quiet mismatch with how the molecule actually works in the body.
Here's what melatonin is, what it isn't, and why our sleep stack is built around four other compounds instead.
What melatonin actually is
Melatonin isn't a sedative. It's a hormone — produced by the pineal gland in response to darkness — that signals to the rest of the body that night has begun. It's a clock signal, not a sleep switch.
The distinction matters. A sedative makes you sleepy by directly modulating the central nervous system (think: benzodiazepines, alcohol, antihistamines). Melatonin doesn't do that. It tells your circadian system "it's nighttime now," and your body's own sleep machinery responds.
For people with a misaligned circadian rhythm — jet lag, night-shift workers, blind individuals with free-running rhythms — that signal is genuinely useful. For someone whose circadian rhythm is fine but who can't fall asleep because their nervous system is wired up at 11 PM, it's the wrong tool. You don't need a stronger night signal. You need the actual brake pedal.
The dose problem
The dose your body produces, naturally, in response to darkness is roughly 0.1 to 0.3 mg across the entire night. That's it.
The dose in a typical OTC melatonin gummy is 3 to 10 mg. Some products go up to 12 mg or 20 mg. That's 30 to 100× the physiological dose, hitting your bloodstream all at once.
A 2017 study by Erland & Saxena tested 31 commercial melatonin products and found that 71% had melatonin content varying from the label by more than 10% — some by over 400%. The category is barely regulated. The pill that says "5 mg" might be 2 mg or might be 24 mg. You don't know.
Even at the labeled dose, you're flooding the system with a hormone signal at 30× the body's intended amount. That's not "supporting" anything. It's overriding.
The grogginess problem
Melatonin has a half-life of roughly 40 to 60 minutes for the released portion, but extended-release formulations and the high doses common in OTC products mean meaningful concentrations stay in the bloodstream for 4 to 8 hours.
That's the next-day fog. The "I slept but I feel hung over" feeling. Your body is still clearing the hormone signal hours after the sun came up. Your circadian system is getting mixed messages — daylight saying "wake up," residual melatonin still saying "it's night." The result is morning grogginess that a lot of people just learn to live with, not realizing the supplement is the cause.
The four ingredients in Moon Milk's sleep stack all clear within hours and have no documented next-day fog effect. That's not an accident — it was a filter.
The downregulation problem
This is the part most people aren't told.
When you flood your system with exogenous melatonin every night, your body responds the way it responds to most exogenous hormones: it downregulates its own production. The pineal gland gets the signal "we have plenty of melatonin already" and dials back endogenous synthesis.
The evidence on this is still developing — long-term human trials are limited — but the mechanism is consistent with how every other hormonal feedback loop in the body works. Take exogenous testosterone, the body suppresses its own. Take exogenous thyroid, same story. There's no obvious reason melatonin would be the one hormone that escapes the rule.
What that means in practice: a lot of people who start on nightly melatonin find that within a few months, they can't sleep without it. The supplement that was supposed to help them sleep has trained their body to not produce its own.
What we use instead
The frame we used designing the Moon Milk sleep stack was: support the mechanisms the body already uses to fall and stay asleep, instead of overriding them with an exogenous compound.
Four ingredients, dosed at study-cited levels, each targeting a different pathway:
Glycine — 3 g
Drops core body temperature by ~0.3°C, the same thermal cue your brain uses to initiate deep sleep. Yamadera 2007 showed it shortens sleep latency and improves slow-wave sleep without next-day grogginess.
Magnesium bisglycinate — 200 mg
Activates the parasympathetic nervous system and is a cofactor for GABA receptor binding. Roughly 50% of Americans don't hit the magnesium RDA from diet — the deficiency is part of why "wired but tired" is so common. Magnesium is also a cofactor for the enzyme that converts serotonin to your own melatonin, supporting endogenous production rather than overriding it.
L-theanine — 200 mg
Quiets mental noise without sedation. Increases alpha-wave activity (the meditative state) and dampens cortisol response. Lyon 2011 demonstrated improved sleep architecture without next-day grogginess.
Apigenin — 50 mg
The active sleep compound in chamomile. Modulates the GABA-A receptor — the same brake-pedal target as benzodiazepines — but without dependence or next-day fog. A cup of chamomile tea has roughly 0.4 mg; we use 125× that, the dose the studies actually tested.
Stacked, these four cover the four mechanisms your body already uses to enter and maintain sleep: thermal signal, parasympathetic state, mental quietness, and GABA tone. They support the system. They don't override it.
Where this fits in the bigger picture
The sleep stack is half of Moon Milk. The other half is 20 g of slow-digest micellar casein, designed to keep amino acids elevated through the entire overnight recovery window — 6 to 8 hours of muscle protein synthesis support.
The sleep stack creates the conditions for deep, restorative sleep. The casein gives your body the raw material to rebuild during it. Both halves of the recovery window, supported in one ritual.
That's the whole product. No melatonin. No shortcut hormone signal. No next-day fog. Just the four-compound stack the studies actually used, paired with the protein the recovery window actually needs.
The bottom line
Melatonin isn't bad. It's misused.
If you're crossing time zones tomorrow, a low-dose (0.3 to 0.5 mg) melatonin can help reset your clock. That's the use case it was studied for. That's the use case it works for.
If you're trying to sleep tonight in your own bed, in your own time zone, after a hard training day, melatonin isn't the lever. The lever is supporting the systems your body already uses — body temperature, parasympathetic state, mental quietness, GABA tone — and feeding the recovery window with slow-digest protein so the rebuild actually happens.
That's Moon Milk. No hormones. No overrides. Just the stack, dosed right.
Muscle isn't built in the gym. It's built while you sleep.