What dosages and durations have long-term human trials of L-tyrosine used, and what adverse events were reported?

1. What trials actually measured — short pulses vs. long courses

Most controlled human research cited in the available sources tests L‑tyrosine acutely or for days around a stressor (for example, 2 g/day for five days during military training) rather than months or years of continuous supplementation ^[3]. Reviews and clinical summaries emphasize short‑term benefit under stress rather than durable, multi‑month maintenance studies ^{[6] [3]}.

2. Common dosage ranges reported in the literature

Clinical reviews and compendia report two clusters of dosing: (a) single acute doses used in cognitive tests — typically 0.5–2 g — and (b) per‑body‑weight regimens of roughly 100–150 mg/kg/day used in some clinical and exercise studies (100 mg per 2.2 lb ≈ ~100 mg/kg produces ~7 g/day for an average adult) ^{[1] [2] [4]}. A nutrition‑science review noted doses in the literature "up to 20 g," but those higher values are exceptions in acute, experimental work rather than routine long‑term prescriptions ^[3].

3. What "long‑term" means in the available reporting

Available sources distinguish acute, mission‑focused use (hours–days) from chronic therapeutic use. Consumer health pages and reviews explicitly state that long‑term safety is not well established and caution against unsupervised, prolonged intake above ~1,000 mg/day — indicating that long‑term trials large enough to establish safety are missing from the cited corpus ^{[4] [5]}. Therefore "long‑term human trials" of continuous high‑dose L‑tyrosine are not clearly documented in these sources ^[4].

4. Reported adverse events and safety signals

Across reviews and health information sites, L‑tyrosine is generally described as having no frequently reported serious short‑term safety signals in trials, but the literature and consumer authorities warn the safety of long‑term use, particularly >1,000 mg/day, is unknown and should be monitored by a physician ^{[4] [5]}. A review of stress‑response studies states that L‑tyrosine cannot be recommended for patients because of lack of long‑term safety evidence despite short‑term cognitive benefits ^[3]. Some popular sources and forums speculate about effects on serotonin balance or mood with prolonged use, but those claims are not substantiated in the clinical trial summaries provided here (p1_s7 — claim present; clinical reviews do not confirm).

5. Conflicting interpretations and potential agendas

Academic reviews focus on mechanistic and short‑term cognitive effects under stress and caution about recommending routine clinical use without longer safety data ^{[6] [3]}. Consumer and supplement sites provide dosing tables that normalize 100–150 mg/kg or suggest daily ranges of 1.5–7 g and emphasize safety at common doses — these outlets have an implicit product‑promotion angle and do not substitute for randomized long‑term safety trials ^{[1] [5]}. Health systems and medical pages (PeaceHealth) recommend medical oversight for long‑term use, reflecting a conservative clinical stance ^[4].

6. What the reporting leaves out (limitations)

Available sources do not describe large, long‑term randomized controlled trials that systematically evaluated continuous L‑tyrosine at high doses (multi‑month to multi‑year) and captured rare adverse events; therefore definitive long‑term safety conclusions cannot be drawn from the provided material (not found in current reporting). Adverse‑event profiles by dose, interaction studies with antidepressants or MAO inhibitors, and formal NOAELs for humans are not detailed in these sources (not found in current reporting).

7. Practical takeaway for clinicians and consumers

Short‑term, stress‑targeted dosing (single doses 0.5–2 g or per‑kg regimens around 100–150 mg/kg for brief courses) underlies most evidence of benefit; however, authoritative summaries warn long‑term safety above ~1,000 mg/day is unestablished and advise physician monitoring before prolonged use ^{[3] [4] [5]}. Consumers should weigh short‑term, context‑specific benefit claims against the absence of robust long‑term trial data and competing messaging from supplement promoters ^{[6] [1]}.

Sources cited in this report: ^[3]; ^[1]; ^[2]; ^[4]; ^[6]; ^[5]; ^[7].