Evidence suggests that the anabolic effect of resistance training is enhanced by ingestion of the branched chain amino acids, particularly leucine. Ingestion of essential amino acids at rest can stimulate protein synthesis, which occurs at the level of messenger RNA via the activation of the mTOR signal cascade. Protein synthesis rates are regulated by both amino acids and exercise and probably under the control of glycogen synthesis. Albumin synthesis is also stimulated by amino acid ingestion and it has been suggested that protein is incorporated into albumin in order to store protein and reduce waste of amino acids through oxidation. The dose of protein needed to cause muscle or albumin protein synthesis has been investigated1. Six healthy young men were given leg-based resistance training followed by protein drinks containing 0, 5, 10, 20 or 40g of whole egg protein.
The results showed that there was a dose response of muscle protein synthesis and albumin protein synthesis to dietary protein ingestion, but stimulation was maximum at 20 grams in both cases. Leucine oxidation was increased after ingestion of 20 and 40 grams of egg protein, but not at lower doses. The oxidation of leucine suggests that maximum incorporationi into amino acid pools occurs at doses of around 20 grams and that any excess protein is oxidised. The authors of the study suggested that protein consumption in excess of 20g 5 to 6 times a day could ultimately lead to oxidative loss. Because of adaptations of oxidation to the amount of amino acids in the diet, chronic protein consumption in excess of this amount could actually reduce the protein synthetic effect in muscle or albumin to suboptimal (<20 gram) doses.
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