Reading time · 9 min
Last updated · 2026
Reviewed against published literature
Most supplement brands hide behind proprietary blends and a wall of marketing. This is the opposite: every ingredient, every dose, and what the research actually supports — written to be read, not skimmed.
There is a version of the supplement industry that runs entirely on hope. A proprietary blend with a proprietary name, dosed at a fraction of what the studies used, sold on the strength of a founder's story and a stock photo of someone sleeping. It works often enough — placebo is real, and most people never check — that there's little commercial pressure to do better.
ARC Nightly™ is built on the opposite bet: that a meaningful number of people would rather read the evidence than be sold a feeling. So this page does something unusual for a product page. It tells you what's inside, at what dose, where it comes from, and what we can and can't claim about it.
The doses are the product. Everything else is packaging.
The longevity research that's reached the mainstream — Attia, Walker, Huberman among others — converges on an unglamorous conclusion: the single highest-leverage thing most people can do for how they age is sleep better, consistently, for decades. Not occasionally. Not heroically. Nightly. Recovery, hormonal regulation, metabolic health, and cognition are all built in the dark, and the deficit compounds quietly until it doesn't.
That framing shaped the formula. We weren't trying to engineer a sledgehammer that knocks you out. We were trying to support the architecture of a good night — the depth of slow-wave sleep, the ease of falling into it, the absence of the 3 a.m. cortisol spike — in a way you could sustain for ten thousand nights without tolerance or grogginess.
Each ingredient earns its place on evidence and dose. Several of them — magnesium, L-theanine, apigenin, glycine — converge on the GABA system, the brain's primary sleep-regulatory pathway.7 Expand any one below for the detail — the mechanism, the dose rationale, and the honest limits of what's known.
Magnesium is involved in hundreds of enzymatic reactions, including those that regulate the nervous system and the sleep-related neurotransmitter GABA. The glycinate form — magnesium bound to the amino acid glycine — is chosen for absorption and for being gentle on the gut, unlike the oxide form that dominates cheap supplements and mostly passes through you.
Why this dose: 400 mg of elemental magnesium sits within the range used in sleep and relaxation research.1 We source from Albion (TRAACS), a supplier that publishes its own chelation data.
Honest limit: magnesium's sleep benefits are most pronounced in people who are deficient — which, given modern diets, is a large share of people, but not everyone.
An amino acid found in tea, L-theanine promotes a state of calm alertness — it takes the edge off without sedating. It's the reason a cup of green tea feels different from a cup of coffee despite the caffeine. At night, it helps quiet the mental chatter that keeps people awake.
Why this dose: 200 mg is the dose most commonly studied for relaxation and sleep quality.2 We use Suntheanine, the patented, pure L-isomer form.
Apigenin is the flavonoid that makes chamomile tea mildly sedating. It binds to GABA-A receptors,3 the same broad system targeted by far harsher sleep drugs, but gently. It's under-marketed precisely because it's cheap and unpatentable — which has nothing to do with whether it works.
Why this dose: 50 mg delivers a meaningful amount of isolated apigenin, far more than you'd get from a realistic number of cups of tea.
Glycine, taken before bed, has been shown to improve subjective sleep quality and the ease of falling asleep, likely by helping lower core body temperature4 — a physiological signal that it's time to sleep. It's also the amino acid bound to our magnesium, so the two work in concert.
Why this dose: 3 g matches the dose used in the sleep studies. This is a gram-scale ingredient, which is part of why ARC is a stick you pour into water rather than a pill you swallow.
Saffron is one of the most studied botanicals for mood and sleep, and almost no one puts it in a nightly formula. It works through a different pathway than the GABA cluster — closer to serotonin — which is why it belongs alongside the others rather than duplicating them.
Why this dose: 28 mg is the exact amount used in the human sleep-quality trials, delivered as affron — the standardized extract those studies were run on.5 Not a dusting for the label; the dose the research actually used.
Honest limit: the sleep evidence for saffron is promising but younger than the base for magnesium or glycine. We dose it at the studied amount and let the certificate of analysis prove it's in there.
Ashwagandha is an adaptogen with a growing body of evidence for reducing cortisol and perceived stress.6 For sleep, the relevant mechanism is clearing the day's stress load so the nervous system can stand down.
Why this dose: 300 mg of KSM-66 — a standardized, full-spectrum root extract — is the dose used in the cortisol-reduction trials.
L-tryptophan is the amino acid your body converts into serotonin and, downstream, its own melatonin. Rather than dosing you with melatonin directly — the thing we deliberately left out — tryptophan gives the body the raw material to run its own overnight chemistry. In controlled work it has shortened the time spent awake after first falling asleep.8
Why we added it: it's the honest way to support the melatonin pathway without overriding it. Why this dose: 1 g sits in the range shown to affect sleep latency and continuity, well below pharmacological levels. We use a pharma-grade source.
Inositol is a naturally occurring sugar alcohol involved in the second-messenger signaling that sits downstream of serotonin and GABA. In controlled trials it has reduced anxiety and the mental restlessness that keeps a busy mind from settling.9 For sleep, its job is quieting the 11 p.m. mind — the loop of tomorrow's list — rather than sedating you.
Why this dose: gram-scale is where inositol's calming effect shows up in the research; a token pinch does nothing. Two grams keeps us in the studied range.
ARC Nightly is a supplement, not a drug. It is not intended to diagnose, treat, cure, or prevent any disease. We don't promise you'll fall asleep in four minutes or wake up a different person. What we promise is that the doses on the label are the doses in the stick, that the ingredients come from the suppliers we name, and that every batch is tested by an independent lab and published for you to read.
That's a lower-drama claim than the category is used to. We think it's the only one worth making.
We don't ask you to take the formula on faith. Each production run is third-party tested for potency, purity, heavy metals, and microbiology — and the Certificate of Analysis is posted by batch number for anyone to read.
Citations refer to claims marked with the corresponding number above. Verify any specific dose or mechanism claim against the original paper before relying on it.