I have read some good and some bad things about BCAAs. They have been around for a long time, like 50 years or more. There isn’t a lot of sound research on them. The majority of the research was paid for by companies producing BCAAs. Many independent studies showed no definitive effects. There were reports of less fatigue and of more fatigue, increased strength and decreased strength, etc. And no one has done a follow up study on the long term outcome that I can find so far. There is no money in bad news, so companies don’t pay for long term studies unless they know the outcome in advance.So no long term study usually means no good news.
But to me it is just another attempt to bypass eating properly and training properly. Another “magic pill” for the masses. Usually it is used by the people who want big muscles or instant results. I can also tell you that the products that usually get you fast results end up costing you fast loses when you stop using them or down the road. Sensible eating and training have never been shown to have side effects or future health bad impacts.