From the results of our study, it can be suggested that there is a tolerance level of BCAA ingestion in rats submitted to prolonged physical exercise. It should be noted that acute and sub-acute toxicity studies of BCAAs using mice and rats and a chronic toxicity study using rats have been reported. In these studies, the BCAA composition used was a 2.1:1:1.2 leucine:isoleucine:valine ratio, and no animals died from the single dose of 10 g of BCAA/kg body weight in the acute toxicity study, and the half-maximal lethal dose was estimated as >10 g/kg body weight. No toxic effects of BCAA were observed at a dose of 2.5 g/kg body weight per day for three months or 1.25 g/kg body weight per day for one year [42]. Furthermore, the studies on BCAA supplementation that have been conducted on physically active humans show that a rather large dietary excess of the three BCAAs is well tolerated when consumed in diets containing surfeit amounts of protein. Ingestion of BCAAs in the diet up to 450 mg·kg−1 body weight per day, which is a little over three times the estimated average requirement, appears to cause no adverse effects in healthy adults [43]. - See more at: http://www.mdpi.com/2072-6643/4/11/1767/htm#sthash.gCoW47sn.dpuf