BCAA
Supplement
amino acid
fitness
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Training support · gains beyond whole protein unproven
When to take
Timing before or after training is not settled
Take with
Complete protein — BCAAs alone lack the other EAAs
Pros & cons
Pros
- Up to 20 g a day in divided doses appears safe
- Some 3–6 week studies: 10–14 g a day aided gains
- Leucine might stimulate protein synthesis in muscle
Cons
- One review calls the anabolic claim unwarranted
- Little evidence in endurance-type events
- Whey and complete proteins already supply them
Sources
- NIH ODS — Dietary Supplements for Exercise and Athletic Performance (Health Professional), BCAA efficacy · read 2026-08-27
what it says
“little evidence to date that supplements of these amino acids improve performance in endurance-related aerobic events … The BCAAs, especially leucine, might also stimulate protein synthesis in exercised muscle”
- NIH ODS — Exercise and Athletic Performance, BCAA dose and muscle mass · read 2026-08-27
what it says
“The results of several short-term studies lasting about 3 to 6 weeks suggest that about 10–14 g/day supplemental BCAAs might enhance gains in muscle mass and strength during training”
- NIH ODS — Exercise and Athletic Performance, BCAA timing · read 2026-08-27
what it says
“it is not clear from existing research whether consumption of protein and BCAAs before versus after a workout affects their ability to maximize muscle protein synthesis and reduce protein catabolism”
- NIH ODS — Exercise and Athletic Performance, BCAA safety · read 2026-08-27
what it says
“Up to 20 g/day BCAA supplements in divided doses appear to be safe … For leucine alone, studies suggest an upper safe limit of intake of 500 mg/kg per day in healthy young and elderly men”
- NIH ODS — Exercise and Athletic Performance, BCAA implications for use · read 2026-08-27
what it says
“Studies have not consistently shown that taking supplements of BCAAs or any of their three constituent amino acids singly enhances exercise and athletic performance, builds muscle mass, or aids in recovery from exercise”
- NIH ODS — Exercise and Athletic Performance, BCAAs from food and protein powders · read 2026-08-27
what it says
“Consuming animal foods containing complete proteins … automatically increases consumption of BCAAs … This is also true of consuming protein powders made from complete proteins, especially whey, which has more leucine than either casein or soy”
- Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? (Wolfe, JISSN 2017) · read 2026-08-27
what it says
“We conclude that the claim that consumption of dietary BCAAs stimulates muscle protein synthesis or produces an anabolic response in human subjects is unwarranted”
- HSA Health Supplements Guidelines (GL-CHPB-3-001 Rev. 020, January 2026), Tables 4–5 · read 2026-08-27
what it says
“HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5”
- HSA Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines (Oct 2025), Annexes A/B · read 2026-08-27
what it says
“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”
- iHerb Singapore — BCAA category page (default sort, 176 results) · read 2026-08-27
what it says
“BCAA … 1 - 48 of 176 results”
Updated 2026-08-30. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.