Do you need a leucine supplement?

No, for most people. Leucine is the amino acid that most strongly switches on muscle protein synthesis (via mTOR). Meals need enough leucine, plus all the other essential amino acids, to get the full response. The ISSN suggests 700–3 000 mg of leucine per protein dose, and in practice about 2–3 g for young adults and about 3 g for older adults.

How much leucine do common proteins give?

Whey is typically about 10–11% leucine by protein weight (it varies by product). That gives these approximate figures:

A typical South African whey scoop supplies about 20–27 g of protein, depending on the product, so one scoop usually reaches the threshold. Meat, fish, eggs and dairy do the same at a normal meal.

Who might fall short?

• Older adults. They need more leucine per meal because of anabolic resistance. A larger protein serving is the first fix. See how much protein older adults need.
• Plant-based eaters. Most plant proteins are lower in leucine. The evidence suggests servings of about 30–40 g, or pea-rice blends, to reach 2–3 g of leucine. Faithful to Nature's Pea Protein Isolate 650 g (R148–R185) costs about R28.46 per 100 g of powder, and USN BlueLab Plant Protein 900 g (R399–R474.99) is about R52.78 per 100 g.
• Dieters eating small, low-protein meals.

Does adding free leucine help?

Not on its own. Adding leucine to a low-protein meal does not fix it, because the other essential amino acids are still missing. Free leucine can also confuse label maths, because added amino acids can inflate a product's apparent protein; see what is amino spiking.

What is the cheapest way to get leucine?

Protein. NPL Platinum Whey Plus 1 kg (R490 at the NPL shop) costs R23.52 per 30 g of protein, which brings about 3 g of leucine plus everything else. An EAA powder such as USN ALL9 Amino 330 g (R359.95–R362.99) costs about R11 per 10 g of powder, and its leucine per serving is not published in text. For picking one, see best EAA supplement in South Africa and BCAA vs EAA.

Any cautions?

Leucine is not a concern at food-level intakes. People with kidney or liver disease, maple syrup urine disease, pregnant women, under-18s and anyone on medication should check with a doctor or dietitian before taking amino powders. Compare proteins at best whey protein in South Africa or best plant protein.

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