A review of 49 studies on a total of 1800 weightlifters, who lifted at least twice a week for at least six weeks, found that doubling the recommended Dietary Allowance (RDA) of protein increased strength gains by nine percent and added about a pound of muscle (British Journal of Sports Medicine, Mar 1,2018;52(6):376-384). With aging, the extra protein offered less muscle growth. The authors found no difference between different sources of protein or whether the extra protein came from food or supplements. They wrote that going to the gym and doing resistance exercise is what makes muscles grow, not taking large amounts of protein from any source.
You need more protein than usual when you are trying to make your muscles larger, but taking in more than twice the RDA for protein causes no additional muscle growth. The recommended daily requirement for the average person is 0.4 grams of protein per pound of body weight. The additional gains in muscle strength from taking extra protein leveled off at 0.7 grams per pound of body weight. Thus when you are doing resistance exercises to grow larger muscles, you need to take in up to twice the RDA for protein and you do not need more protein than that. You can easily accomplish this just by eating more food.
