Your body needs nitrogen to make proteins in your muscles, skin, blood, hair, nails and DNA. You obtain nitrogen from protein-containing foods in your diet, according to the Royal Society of Chemistry. These foods include meat, fish, legumes, nuts, eggs, milk and other dairy products.
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Your body needs the nitrogen in amino acids from protein foods to make other amino acids it uses to synthesize human proteins, according to Virtual Chembook at Elmhurst College. Not only do your various tissues contain protein, your metabolic processes depend upon enzymes, all of which consist of various kinds of proteins. The nucleic acid DNA, which makes up your genes, and RNA, which is involved in protein synthesis, also contain nitrogen.
Normal growth, cell replacement and tissue repair all require nitrogen for production of new cells. Although nitrogen is abundant in the environment, humans cannot directly use it from the air or soil, but instead depend on microbes and green plants to convert it into form our bodies can use. Your body is constantly recycling nitrogen from amino acids. If amino acids are not used for protein synthesis, they can be broken into components, including nitrogen, to produce energy. Nitrogen can also be used to make other types of compounds that aren't proteins, such as the heme in hemoglobin, which carries oxygen in red blood cells.
A healthy adult male needs about 105 milligrams of nitrogen per kilogram, or per 2.2 pounds per day. About 0.83 gram of protein per kilogram per day is considered sufficient to cover nitrogen requirements, according to the International Dairy Foundation. That means a 220-pound man would need 83 grams, or about 3 ounces, of protein a day to supply his nitrogen needs. The breakdown of protein results in ammonia, a nitrogen-containing byproduct that your body eliminates.
Your body eliminates ammonia by converting it to urea, which your kidneys then excrete in urine. In this way, nitrogen is returned to the environment. Unlike populations in underdeveloped countries, Americans do not commonly suffer from a lack of dietary nitrogen unless they are on extreme diets that do not contain sufficient protein. Symptoms of deficiency include hair loss, delayed wound healing, muscle weakness and wasting, brittle hair and hair loss.