Protein
A considerable amount of research has evaluated dietary protein needs of athletes. Although there is some debate, most studies indicate that in order to maintain protein balance during intense resistance and/or endurance training, athletes should ingest approximately 1.3 to 1.8 g protein per kg body mass per day (Butterfield, 1991; Lemon, 1998; Kreider et al., 1993; Kreider, 1999). Athletes training at high-altitude may need as much as 2.2 g protein per kg per day in order to maintain protein balance (Butterfield, 1991). This protein intake is about 1.5 to 2 times the recommended dietary allowance (RDA) for the normal adult. In most instances an iso-energetic diet can provide the required protein, but athletes who maintain hypo-energetic diets, do not ingest enough quality protein in their diet, and/or train at altitude may be susceptible to protein malnutrition (Kreider, 1999). In theory, this state could slow tissue growth and/or recovery from training. On the other hand, ingesting more protein than necessary to maintain protein balance during training (e.g., > 1.8 g/kg/d) does not promote greater gains in strength or fat-free mass (Lemon et al., 1992; Tarnopolsky et al., 1992). These findings indicate that athletes typically do not need to supplement their normal diets with protein, provided they ingest enough quality protein to maintain protein balance.
More recently, there has been interest in determining the effects of pre- and post-exercise carbohydrate and protein feedings on hormonal responses to exercise (Cade et al., 1992; Chandler et al., 1994; Roy and Tarnopolsky, 1998; Tarnopolsky et al., 1997; Zawadzki et al., 1992). Ingestion of protein with carbohydrate has been reported to increase insulin and/or growth hormone levels to a greater degree than ingestion of carbohydrate alone (Chandler et al., 1994; Zawadzki et al., 1992). Consequently, ingesting protein and carbohydrate prior to exercise may serve as an anti-catabolic nutritional strategy (Carli et al., 1992). Further, ingesting carbohydrate and protein following exercise may promote a more anabolic hormonal profile, glycogen resynthesis, and/or hasten recovery from intense exercise (Roy and Tarnopolsky, 1998; Roy et al., 1997). Over time these alterations may allow an athlete to tolerate training to a greater degree and/or promote greater training adaptations, but the evidence is not yet clear.
Obviously you need protein to build muscle mass, whether you get your protein from supplements or cans of tuna, pieces of steak, chicken breasts, etc. it is up to you, but you NEED protein to build muscle mass.