Leucine builds muscle

Twenty-five grams of whey protein contains about 3g of leucine, the amount shown to produce maximal rates of muscle protein synthesis. Researchers wondered if it might be possible to achieve similar results with less whey by adding additional leucine.

Researchers had subjects ingest either 25g of whey protein isolate alone or 6.25g of whey with 3g of added leucine after rest and again after exercise. Compared to fasting, rates of muscle protein synthesis up to 5 hours after the feedings of either whey or whey plus leucine were significantly increased, but were similar between both test groups. However, when comparing the groups 3 to 5 hours after resistance exercise, the whey-only group resulted in nearly a two-fold greater increase in muscle protein synthesis.

These findings show that adding leucine to smaller amounts of whey can provide benefits similar to larger amounts of whey during rest (non-exercising conditions), but that 25g of whey alone provides a more sustained increase in muscle protein synthesis after resistance exercise.

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