Your body needs dietary protein to keep all your cells functioning normally and is especially important for your nervous system. When you consume protein-rich foods, your digestive system breaks their proteins down into amino acids, the basic protein building blocks, and uses these amino acids to fuel many biochemical reactions and to make new proteins. One amino acid, called D-aspartic acid -- more commonly called aspartic acid -- fuels enzyme reactions that have many functions, including producing energy your cells need. Your cells can make aspartic acid, so you don't typically need it as part of your diet, but several foods can boost your intake anyway.
Poultry and Meat
Muscle tissue is especially high in proteins and the amino acids that make them up. Because of this, meats and poultry are generally good sources of aspartic acid. For example, one average-sized beef fillet provides about 4.5 grams of aspartic acid, and a 3-ounce portion of beef pot roast contains about 2.4 grams. One cup of chopped, roasted chicken breast meat provides 3.7 grams of aspartic acid, while an equal amount of turkey meat, either light or dark, contains 2.8 grams. Other types of meat and poultry, including duck, squab, pork and lamb, are also good sources of aspartic acid.
Eggs and Dairy Products
One cup of chopped, hard-boiled egg contains 1.7 grams of the amino acid, and a 1-cup serving of nonfat milk provides about 0.7 gram. Cheese is also a good source of aspartic acid -- 1/2 cup of Parmesan cheese contains 1.3 grams, and 1 cup of diced, part-skim mozzarella cheese provides about 2.5 grams. Other goods sources include provolone, cheddar and Swiss cheese, with between 2 and 2.3 grams in 1 cup of chopped cheese. Other dairy foods such as yogurt, cream and butter are also good sources of aspartic acid.
Some grains, grain-based foods and vegetables also provide moderately high amounts of aspartic acid. For example, 1 cup of uncooked oat bran or parboiled, long-grain white rice contains about 1.5 grams, while 1 cup of corn provides about 1 gram. Protein-fortified, dry spaghetti contains about 0.6 gram in 5 ounces, while 1 cup of enriched vegetable macaroni contains about 0.5 gram. Other grains, such as amaranth, barley, millet and buckwheat, also contain moderately high amounts of aspartic acid.
A 1-cup serving of ready-to-eat, protein-fortified cereal generally contains between 0.3 and 0.5 gram of aspartic acid, depending on the brand. Some dried fruits also contain moderately high amounts of the amino acid, including dried peaches and apricots, with about 0.8 gram in 1 cup. Fresh fruits such as nectarines, cherries, plums and bananas also provide aspartic acid, with 0.5 to 0.6 gram per 1-cup serving.