In the current study we wanted to investigate the anabolic properties of branched-chain amino acids (BCAA; leucine, isoleucine and valine) and their ketoanalogues, the branched-chain ketoacids (BCKA; ketoleucine, ketoisoleucine and ketovaline).

BCKA do not contain nitrogen in their molecular structure and can, therefore, be of particular interest for clinical populations such as patients with chronic kidney disease, as these patient populations have difficulties to excrete nitrogen.

To investigate the effects of BCAA and BCKA ingestion on muscle protein synthesis, we compared it with the ingestion of an equivalent amount of high-quality protein. We assessed the muscle protein synthetic response to the ingestion of 6 g BCAA, 6 g BCKA and 30 g milk protein in healthy, older males.

In the current study we observed that ingestion of BCAA, BCKA, and milk protein all stimulated muscle protein synthesis over the first 2 hours after ingestion, with no differences between treatments. However, the next 3 hours (2-5 h) elevated muscle protein synthesis rates were only observed following the ingestion of milk protein.

We concluded that BCAA, BCKA and milk protein all have strong anabolic properties, but that these effects are short lived following BCAA and BCKA ingestion when compared to the ingestion of milk protein.