Correct, Leucine is the key amino acid to trigger protein synsthesis and the 2.5-3g levels is generally thought of in most people to be the amount needed. However, 3 scoops of Huel has over 2.9g leucine so is about the right amount.
BCAAs are over-rated, but leucine is the one. If you’re getting enough at each meal (Huel, food or protein powder) then great, otherwise some bodybuilders may wish to add supplemental leucine. But 3 scoops of Huel in one serving is fine.
I’m a recrational bodybuilder and last autumn I lost 3 stone of muscle due to illness. I have regained most of this since Feb by including 3-4 x 3 scoop Huel servings per day (and some other food).
@GTIPuG you should be having 3-4 scoops per shake of Huel to get your Leucine hit. I only take 1-2 scoops so the BCAA’s are needed. Sometimes I’ll thrown in a scoop of protein powder which is another good tip.
"How do BCAAs help you gain weight and build muscle?
Whey protein does contain Branch Chain Amino Acids — but it takes a while for your body to access them. Even though whey is the quickest absorbing protein source, it will take several hours for your body to access all of the BCAAs through digestions. BCAA supplements bypass the whey digestion process and enter you bloodstream immediately, causing an even more powerful protein synthesis." https://musclebuilding.pro/blog/best_supplements_to_gain_weight_and_build_muscle/
Despite the popularity of BCAA supplements we find shockingly little evidence for their efficacy in promoting MPS or lean mass gains and would advise the use of intact proteins as opposed to a purified combination of BCAA that appear to antagonize each other in terms of transport both into circulation and likely in to the muscle (Churchward-Venne et al., 2014).