What is BCAA?
And how to best maintain muscle on a deficit? What foods/exercises to eat/do?
I recently investigated whether to buy EAA or BCAA supplements and found this website's summary very helpful (although I am aware it is biased as it is clearly trying to sell EAA supplements). To try to answer your question...
Proteins are made up of amino acids
Our bodies are able to produce some amino acids on its own
But there are nine "Essential Amino Acids" (EAAs) that our bodies are not capable of synthesizing so it is "essential" that we consume these (eg foods/supplements)
Three of these EAAs are particularly involved in muscle metabolism/building - they are known as Branched-Chain Amino Acids (BCAAs - named as such due to their chemical structure) - and are the amino acids Leucine, Isoleucine and Valine.
You can buy BCAA supplements, which are often stated as a ratio of the amino acids. Eg. "2:1:1" is a popular ratio of Leucine : Isoleucine : Valine.
However a recent trend has been to supplement all 9 of the EAAs, rather than just focusing on just the 3 BCAAs.
I'm still not sure which is better for muscle building or overall health, but since I'm trying to make more and more vegan choices and am more likely to be deficient, I purchased these EAAs from Amazon which got good reviews. They only seem to have 8 EAAs though, I'm not sure why they excluded Histidine?