Ingredient
L-Leucine
Research dose
2–3 g
Evidence: Moderate Taken before training: what counts is the amount in the serving you take.
The ISSN's 2018 review: at least 2 g of leucine in one dose is needed to switch on muscle building; the 2017 protein position stand puts a dose's leucine at up to 3,000 mg. Leucine works as part of a complete dose of essential amino acids, not on its own.
Sources
Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
Supports the research dose. Where: Position point 6: "Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs)". Read the source, checked 9 Oct 2026.
Kerksick CM, Wilborn CD, Roberts MD, et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15:38.
Supports the research dose. Where: Performance enhancement supplements, section "Essential amino acids (EAA)": "ingestion of at least 2 g of the essential amino acid, leucine, is required to stimulate cellular mechanisms controlling muscle hypertrophy". Read the source, checked 9 Oct 2026.
BCAA supplements we've checked
23 BCAA supplements, each judged on how much a day its label's own directions give. See them all, ranked.
In the pre-workouts we've checked
| Product | Per scoop | Verdict |
|---|---|---|
| NutraBio PRE | 3.5 g | Effective dose |
| Nutrex Outlift | 2 g | Effective dose |
| Kaged Pre-Kaged Stim-Free | 4.75 g | Effective dose |
| Animal Fury | In a blend | Hidden in a blend |
| JYM Pre JYM | 3 g | Effective dose |
| Gnarly Pre-Workout | 2 g | Effective dose |
| Just Ingredients PreWorkout | 1 g | Below research dose |
| RSP Nutrition AminoLean | In a blend | Hidden in a blend |