{"ok":true,"entry":{"slug":"tyrosine","kind":"supplement","name":"tyrosine","aliases":["L-tyrosine","N-acetyl-L-tyrosine","NALT"],"brands_sg":["California Gold Nutrition","NOW Foods","Doctor's Best","Natural Factors","Jarrow Formulas"],"class":"amino acid","tags":["cognitive","energy"],"use_for":"short-term stress or heavy mental load · effects vary","use_after":"daily","use_duration":"the 4 g/day safety trial ran 4 weeks","take_with":null,"pros":["cognition better under short-term stress or load","up to 4 g/day for 4 weeks was tolerated in 30 men","sg listings run 500–750 mg a capsule"],"cons":["reports on effectiveness vary considerably","physical-exercise potential looks minimal","safety data is 4 weeks, 30 healthy men, one trial"],"dose_note":"sg listings run 500–750 mg of l-tyrosine a capsule; a randomised double-blind crossover in 30 healthy adult men gave graded doses of 0, 1, 2, 3 or 4 g a day for 4 weeks and reported 4 g/day as the highest tested intake without observable adverse effects, which its authors call a noael under those conditions; the review behind the cognitive line covers short-term stressful or cognitively demanding settings, not long-term daily use; no rda, ul or daily value exists for tyrosine; hsa sets no daily limit for it (tables 4–5 cover vitamins and minerals only) and tyrosine is not listed in its oct 2025 prohibited/restricted annex a/b","dosage":{"ul":null,"unit":"mg","fda_dv":null,"rda_ai":null,"ul_status":"none_established","population":"general adult","hsa_max_daily":null},"ul_status":"none_established","sg_class":null,"cautions":["benefit needs intact neurotransmitter function, per the review","safety evidence here is 4 weeks in 30 healthy adult men","clinical conditions — the review calls the potential limited","not listed in hsa's annex a/b — hsa says that list is not exhaustive"],"clashes":[],"sources":[{"id":"jongkees2015","url":"https://europepmc.org/article/MED/26424423","label":"Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands — a review (Jongkees et al., J Psychiatr Res 2015;70:50-57; PMID 26424423) — conclusion","quote":"TYR does seem to effectively enhance cognitive performance, particularly in short-term stressful and/or cognitively demanding situations. We conclude that TYR is an effective enhancer of cognition, but only when neurotransmitter function is intact and DA and/or NE is temporarily depleted.","accessed":"2026-08-27"},{"id":"jongkees2015_vary","url":"https://europepmc.org/article/MED/26424423","label":"Jongkees et al., J Psychiatr Res 2015 — variability across studies","quote":"reports on the effectiveness of TYR supplementation vary considerably, with some studies finding beneficial effects, whereas others do not","accessed":"2026-08-27"},{"id":"jongkees2015_limits","url":"https://europepmc.org/article/MED/26424423","label":"Jongkees et al., J Psychiatr Res 2015 — limits in clinical disorders and physical exercise","quote":"The potential of using TYR supplementation to treat clinical disorders seems limited … Likewise, the potential of TYR supplementation for enhancing physical exercise seems minimal as well","accessed":"2026-08-27"},{"id":"tyrosine_safety2026","url":"https://europepmc.org/article/PMC/PMC13304972","label":"Evaluation of the Safety and Tolerability of L-Tyrosine Supplementation in Healthy Adult Men: A Randomized Crossover Trial (Nutrients 2026; PMID 42356406) — conclusion","quote":"Four-week supplementation with L-tyrosine at doses up to 4 g/day was well tolerated in healthy adult men and was not associated with biochemical and clinically relevant adverse effects under the conditions of this study.","accessed":"2026-08-27"},{"id":"tyrosine_safety2026_design","url":"https://europepmc.org/article/PMC/PMC13304972","label":"L-Tyrosine safety and tolerability crossover trial (Nutrients 2026) — design and doses","quote":"In a randomized, double-blind, placebo-controlled crossover trial, 30 healthy adult men received L-tyrosine at graded daily doses (0, 1, 2, 3, or 4 g/day)","accessed":"2026-08-27"},{"id":"tyrosine_safety2026_noael","url":"https://europepmc.org/article/PMC/PMC13304972","label":"L-Tyrosine safety and tolerability crossover trial (Nutrients 2026) — NOAEL statement","quote":"These findings suggest that 4 g/day represents the highest tested intake level without observable adverse effects and may serve as the NOAEL","accessed":"2026-08-27"},{"id":"hsa_hs_guidelines","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA — Health Supplements Guidelines GL-CHPB-3-001 Rev. 020 (January 2026), s3.1 working definition + clause 4.8","quote":"Vitamins, minerals, amino acids, fatty acids, enzymes, probiotics and other bioactive substances … HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.","accessed":"2026-08-27"},{"id":"hsa_pr_notlisted","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA — Guidelines on Prohibited and Restricted Ingredients in HS and TM, GL-CHPB-1-012 Rev. 001 (Oct 2025), clause 1.3 + Annex A/B — searched, no row for tyrosine","quote":"The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list.","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/l-tyrosine","label":"iHerb Singapore — 'L-Tyrosine' category page, default order, 1 - 43 of 43 results","quote":"California Gold Nutrition, Adrenal Support with L-Tyrosine … NOW Foods, L-Tyrosine, 500 mg … NOW Foods, L-Tyrosine, 750 mg … Doctor's Best, L-Tyrosine, 500 mg … Natural Factors, L-Tyrosine, 500 mg … Jarrow Formulas, L-Tyrosine, 500 mg","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:33.302383+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}