The L-Tyrosine Dose Gap: Why a 500 mg Capsule Isn't a Dose
Educational summary — not medical advice.
The short answer
Two things stand between the tyrosine on the shelf and the tyrosine in the research. Axis 1 — the dose gap. Trials used ~2 g up to 100–150 mg/kg (7–13 g) of plain tyrosine before a stressor, so a 500 mg capsule is only ~¼ of the low end — and as little as ~1/26 of the highest weight-based doses. Plain powder is the fix: a scoop is 1–2 g at ~$0.05–0.08/g. Axis 2 — NALT. "N-acetyl-L-tyrosine," sold as "more bioavailable," is actually poorly converted: an IV study found 56% excreted unchanged (Magnusson 1989), so per mg it delivers less usable tyrosine.
Axis 1: the studied dose dwarfs a capsule
Tyrosine's cognitive trials didn't use a small daily pill — they used a large single pre-load before an acute stressor. The low end is about 2 g, and the weight-based studies used 100–150 mg/kg, which is roughly 7–13 g for a typical adult (Jongkees 2015; Shurtleff 1994 used 150 mg/kg). Against that, a 500 mg capsule is about a quarter of the 2 g floor, and a small fraction of a weight-based dose. The milligram number on a capsule looks like a dose; measured against the research, it's a rounding error.
| Reference point | Amount | 500 mg capsules to reach it |
|---|---|---|
| One 500 mg capsule | 0.5 g | 1 |
| Low studied dose | ~2 g | 4 — the capsule is ~¼ of this |
| Weight-based, 100 mg/kg (70 kg) | ~7 g | ~14 |
| Weight-based, 150 mg/kg (85 kg) | ~13 g | ~26 |
The fix: powder scoops to a real dose
Because the dose is measured in grams, the format that reaches it is plain powder — a single scoop is 1–2 g, and it costs a fraction per gram of what capsules do. Priced per gram of actual tyrosine, powders run ~$0.05–0.08/g versus ~$0.14–0.38/g for capsules. So powder wins twice: it's the only format that comfortably reaches a studied dose, and it's the cheapest per gram while doing it.
Axis 2: NALT is sold as an upgrade — but it's poorly converted
The second trap is N-acetyl-L-tyrosine (NALT), an acetylated form marketed as "more soluble" and "more bioavailable." The soluble part is true; the bioavailable part isn't, at least not for delivering usable tyrosine. In a human intravenous study, 56% of an NALT dose was excreted unchanged in the urine and plasma tyrosine rose only about 25% (Magnusson 1989) — meaning the body poorly deacetylates NALT into free tyrosine, so much of it is simply lost. Per milligram, NALT delivers less usable tyrosine than plain L-tyrosine.
Put together First gap: the studied dose is ~2 g up to 7–13 g before a stressor, so a 500 mg capsule is ~¼ of the floor — and plain powder is the only cheap way to reach a real dose. Second trap: NALT is poorly converted (56% excreted unchanged by IV; Magnusson 1989), so it delivers less usable tyrosine per mg — an "N-acetyl" premium for less active. Of 11 products we track, 2 are plain powders and 2 are NALT. Shop on cost per gram of plain tyrosine, not on the capsule count or the "bioavailable" label.
What to actually do
- Buy plain tyrosine powder to reach a dose. A scoop is 1–2 g at ~$0.05–0.08/g — the only format that comfortably hits the ~2 g studied dose. See the cost-per-gram ranking.
- Don't treat a 500 mg capsule as a dose. It's ~¼ of the floor; reaching a real dose from capsules means four or more at once — use the capsule calculator to see your number.
- Skip the NALT premium. It's poorly converted, so per milligram it delivers less usable tyrosine than plain L-tyrosine.
- Remember it's stress-only. Even a perfect dose only helps under acute stress, not as a daily focus pill.
Frequently asked questions
Is a 500 mg capsule enough?
No — the studied dose is ~2 g up to 100–150 mg/kg (7–13 g). A 500 mg capsule is ~¼ of the 2 g floor and as little as ~1/26 of the highest doses. Powder, which scoops to 1–2 g, is the practical way to reach a real dose.
Why is powder better than capsules?
The dose is in grams; capsules hold fractions of a gram. Powder scoops 1–2 g at ~$0.05–0.08/g; capsules run ~$0.14–0.38/g and top out at 500–1000 mg. Reaching the 2 g floor takes 4 capsules, or a single scoop.
Is NALT better absorbed?
No — it's poorly converted. An IV study found 56% excreted unchanged and plasma tyrosine up only ~25% (Magnusson 1989), so per mg it delivers less usable tyrosine than plain L-tyrosine.
Does NALT do nothing for the brain?
That overstates it. Magnusson was IV and measured plasma tyrosine, not brain outcomes — so it shows poor conversion to circulating tyrosine, not zero cognitive effect. The bounded conclusion: NALT is an inefficient way to raise usable tyrosine per mg.
Related
- Best value — every product ranked by cost per gram of tyrosine (NALT priced separately)
- Dosage guide — ~2 g up to 100–150 mg/kg + a "how many capsules" calculator
- Does it work? — the stress-only evidence and the safety cautions
Sources
- Magnusson I, et al. "N-acetyl-L-tyrosine and N-acetyl-L-cysteine as tyrosine and cysteine precursors during intravenous infusion in humans." Metabolism. 1989. PMID: 2507878 (56% of NALT excreted unchanged; plasma tyrosine +25% — poorly deacetylated; IV/plasma study, not brain outcomes).
- Jongkees BJ, et al. "Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands — a review." J Psychiatr Res. 2015. PMID: 26424423 (studied dose ~2 g up to 100–150 mg/kg, taken before the stressor).
- Shurtleff D, et al. "Tyrosine reverses a cold-induced working memory deficit in humans." Pharmacol Biochem Behav. 1994. PMID: 8029265 (150 mg/kg dose).
- Manufacturer labels and live Amazon pricing for all listed products, July 2026. Full dataset: /l-tyrosine/cost-by-brand.json (CC BY 4.0).