Protein is broken down in the stomach to create the 20 types of amino acid needed to grow and maintain every kind of tissue in the human body. These are divided into two categories, nine essential and eleven non-essential amino acids. Essential acids do not necessarily perform more important tasks, but they are so named because they cannot be produced by the body and so must be gathered from diet.

While it is true that large amounts of protein are needed to build muscle mass, the average American easily meets, and exceeds, the daily recommended amount of protein. The recommended daily intake is 46 grams for women and 56 for men. Eating more protein than your body needs is not usually dangerous for those without organ disease, but it does saddle you with excess calories, which can cause weight gain. Higher intake is reasonable for those who are highly active or want to build muscle mass.

Protein can be found in a large variety of foods, though animal tissue is the largest source. Animal tissue almost always contains all of the essential amino acids, and it carries these amino acids in a form that is easier for our body to utilize. This includes not just meat, poultry, and fish, but also animal derivatives like eggs and cheese. 

Vegetarians must be more careful to monitor their intake, but they can add sufficient protein to their diet with tofu, beans, and nuts. As every vegan source of protein, except for soybean, does not contain all of the essential amino acids by itself, they must be combined in balanced meals to ensure that your body gets everything that it needs to function.

Here are some examples of the protein content of common foods:
      - One cup of milk has about 8 grams of protein
      - An eight-ounce container of yogurt has about 11 grams of protein
      - One cup of dry beans has about 16 grams of protein
      - A three-ounce piece of meat has about 21 grams of protein

While this is just one example, the combination of these foods at those portions would constitute a balanced diet for a day and supply 56 grams of protein, the recommended amount for men. Now that you have learned the basics about protein, you are equipped to research and put together your own balanced meals.