The building block of protein is the element, Nitrogen. When we speak about protein and its requirements in the diet, we speak in terms of nitrogen. Since every protein has nitrogen in it, we can follow what is happening in the body with protein by following the nitrogen. There are obligatory losses of nitrogen in the urine and intestines every day. This loss of nitrogen corresponds to 25 to 30 grams of protein per day in the normal healthy adult. To compensate for these losses, 50 to 60 grams of protein intake are required in the diet to maintain nitrogen balance in the normal adult. To promote a positive nitrogen balance, it is recommended that the protein intake be greater than 70 grams of protein per day.
Excess protein in the diet, as mentioned above, is not stored as protein but rather is converted to fat. Additionally, the filtering of the blood that occurs in the kidneys is effected by excess protein. In other words, too much protein is hard on the kidneys and may lead to kidney damage by injuring the filtering networks of the kidneys.