Resistance exercise is the primary stimulus for muscle growth, but nutritional support is important too, especially in the form of protein from either animal- or plant-based foods. The current recommended dietary allowance, or RDA for protein intake is 0.8 grams per kilogram of bodyweight (about 0.36 grams per pound) per day, or about 68 grams for a 150-pound adult. Dr. Phillips asserts that this amount of protein is probably not enough to maintain muscle mass. He believes that eating 1.2 to 1.6 grams of protein per kilogram of bodyweight is likely optimal for muscle protein synthesis, especially as one ages. In this clip, Dr. Stuart Phillips discusses his concerns regarding the current protein recommended dietary allowances.