Your body uses amino acids from food to manufacture hundreds of proteins and to fuel many biochemical reactions in your cells. Essential amino acids are those you can't make and need to obtain from your diet. One of these, leucine, helps determine the specific shape of certain proteins, which is important in helping them perform their functions. Many common foods are rich sources of this amino acid.
Meat, Poultry and Fish
Leucine is found in the lean portion of meats and poultry, which are generally leucine-rich. For example, a 5-ounce serving of beef fillet contains 4 grams of leucine, while 1 cup of chopped, cooked chicken light meat or an average-sized pork loin chop contains about 3.5 grams. Most types of fish are also rich sources of leucine. These include canned light tuna, with 3.5 grams in 1 cup of tuna chunks, and salmon and haddock, which have about 3 grams of leucine in an average-sized filet. Other fish that are good leucine sources include whitefish, tilefish and trout.
Dairy products are good sources of leucine because they tend to be high in protein. For example, 1 cup of nonfat cow's milk provides 0.8 gram of leucine and slightly more if it's protein-fortified or has added nonfat milk solids. Most types of cheese are also sources of leucine -- a 1-ounce serving of edam, Colby, cheddar or bleu cheese provides between 0.5 and 0.7 gram of leucine, while Parmesan is a bit higher, with about 1 gram per ounce of hard cheese. Most types of yogurt also contain moderate amounts of leucine, with about 1 gram per 6-ounce container.
Legumes and Other Foods
Because they're rich in protein, legumes are also quite high in leucine. For example, 1 cup of raw soybeans provides about 6 grams, white and kidney beans each contain 3.7 grams per cup and 1 cup of lentils provides 3.4 grams. Soy-based foods are also good leucine sources -- for example, 1 cup of tempeh, a fermented soy food, provides 2.4 grams. Other good sources include dried spirulina, a seaweed product, with almost 3 grams in 1/2 cup, and peanuts, which have 1.4 grams of leucine in 1/2 cup.
Benefits and Recommendations
Eating a diet high in leucine is generally healthy because it provides your body with a steady supply of this essential amino acid, which you aren't able to store for any length of time. A review paper published in the May 2010 issue of "Nutrition Reviews" summarizes the benefits of leucine, highlighting its ability to stimulate insulin production, helping control blood sugar. It also indicates that increasing dietary leucine may help control obesity and help keep blood cholesterol in a healthy range. Over time, leucine may also have positive effects on liver and muscle cells. If you have questions about dietary leucine, discuss them with your doctor or a registered dietitian.