BCAA (branched-chain amino acids)

What it is

BCAA stands for the branched-chain amino acids leucine, isoleucine and valine. All of them are essential, so they come from food, and unlike most amino acids they are broken down mainly in muscle rather than in the liver; leucine is the strongest single trigger of muscle protein synthesis. They are used around training for physical performance.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Physical performance

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

Timing is flexible and food makes little difference. The point worth spelling out is the one on the label: these are not a complete protein source. Building muscle protein needs the full set of essential amino acids present together, so where total protein intake is already adequate a BCAA drink adds little, and where intake is low it cannot stand in for real protein or for a complete amino acid blend. Free amino acids are absorbed quickly, and a concentrated drink taken alone can unsettle the stomach.

When to see a doctor

Liver or kidney disease, or any known disorder of amino acid metabolism, is a reason to see a doctor before using concentrated amino acids; lasting fatigue or loss of muscle despite training and supplementing points to a diet problem that deserves proper assessment.

Worth knowing

• Not a complete protein source