You need to get an adequate amount of high quality protein every day to build muscle. You also need carbohydrates in your diet and enough vitamins. I take a multivitamin every day. I drink a couple of servings of skim milk daily. I eat small servings of low fat meat and lots of fruits and vegetables as well some whole grain bread. The further you get away from premixed, ready made, processed crap the better off you will be. You should be eating natural foods.
Good: broiled fish, steamed broccoli, steamed squash, home made whole wheat rolls, an apple, an orange, skim milk
Bad: Twinkies, Coka Cola, Ramen noodles Balanced Diet Nutrition - Nutrition, Function, Side Effects - NY Times Health Information