I hear of a lot of people using hemp whey protein powder & other plant based proteins as their main protein sources when trying to either preserve or gain muscle tissue. This is not effective.
Proteins are made up of amino acids (AA), these are the building blocks our body uses to repair our muscles. These are split into two main categorised, essential amino acids and non-essential amino acids.
Our body has the ability to make it's own non-essential AA if required but essential AA must be obtained from your diet. Animal proteins are high in essential AA whilst plant proteins and low in essential AA and high in non-essential AA. Repairing muscle cells requires all the amino acids and as your body already has the capacity to create it's own non-essential AA it's the ones found in animal proteins that are needed most from our diet.
I am not saying plant proteins are bad, they are a great way of filling you up and providing amino acids for cell repair, however, they alone are not sufficient for optimal muscle repair/growth.
Good Animal Protein Sources: Eggs / Lean Beef / Fish / Greek & Goats Cheese / Chicken / Turkey / Other lean game meats