Beef and Poultry

• Nine essential amino acids make up a complete protein. Beef and poultry are among a select few foods in which complete proteins can be found. Cooked lean cuts of beef, pork or ham contain about 25 grams of protein, which is half the daily value the USDA recommends These meats are also rich in zinc, iron and vitamin B12. White poultry meats, such as turkey and skinless chicken, are low in fat and high in nitrogenous protein. The USDA recommends that when eating meats, an adult should consider 2 to 3 ounces as an average serving size.
  
  

Fish

• Seafood is a nitrogen-rich healthy option in which complete proteins can be found. A half-fillet of Atlantic or Pacific halibut contains 42.44 grams of protein -- nearly 85 percent of the USDA recommended daily value. Salmon, which contains 42.33 grams of protein, is additionally a good source of omega-3 fatty acids. Omega-3 fatty acids have been shown to decrease triglyceride levels and lower blood pressure. The American Heart Association recommends that adults should eat a 3.5 ounce serving of fish at least twice a week.
  
  

Dairy Products

• Dairy products are another nitrogen-rich option that contains all nine amino acids. A one-cup serving of 2 percent milk or low-fat cottage cheese contains 31.05 grams of protein -- 62 percent of the USDA-recommended daily value. An 8-oz.container of plain, skim milk yogurt contains 13 grams of protein. Studies indicate that eating yogurt on a regular basis may help to boost the immune system, as well as regulate the digestive tract. In addition to being high in nitrogen, dairy products are rich sources of calcium, which helps to strengthen the structure and function of bones and teeth.
  
  

Beans and Nuts

• While beans and nuts are rich in nitrogen, they considered a source of incomplete proteins, which lack at least one of the nine essential amino acids. One cup of chickpeas, navy, pinto, kidney or black beans all contain approximately 14 to 16 grams of protein -- 30 percent of the recommended daily value. Additionally, nuts such as almonds, peanuts, cashews and pecans are packed with protein and fiber. A handful of almonds contains 10 percent of the recommended daily value and is high in vitamin E, which is believed to help fend off heart disease and cancer.