Carbohydrates should be 55-65% of your caloric needs. Carbohydrates are the most important nutrient for exercising muscle but protein is what
repairs the muscle damaged during the workout.
Stored carbohydrates, in the form of glycogen, are the primary fuel source for exercise. It's recommended that you get about 2.7g of carbohydrates per lb of bodyweight depended upon the activity level. So carbohydrates are your fuel source for exercising, but you cannot repair without protein.
Here's the recommended nutrient intakes.
Protein --- 12-20% of your calories
Carbohydrates --- 55-65% of your calories
Fats --- 25-30% of your calories
Of course it's depended upon goals and metabolism, but that's the general guideline.
You need ideally
both to build muscle, but the two play separate roles. Protein isn't a primary source of energy but repairs damaged muscle tissue and carbohydrates (preferably complex carbohydrates) are the primary energy source of exercising muscles, so the two both play vital roles but both are necessary to build muscle.
<message edited by MVP on Saturday, June 13, 2009 7:15 PM>