Leucine and Valine

Amino acids play an important role in our bodies as building blocks of protein, a fuel source for muscles. Protein substances make up your muscles, tendons, glands and organs. Like water, amino acids are found abundantly throughout your body. Leucine and valine are two of 20 amino acids your body uses to function. Your body can produce some amino acids on its own, while dietary intake of others is necessary.

Function

Your body cannot manufacture leucine or valine, making dietary intake crucial. Both amino acids are two of three nutrients known as branched-chain amino acids, or BCAAs, that account for a third of your muscle tissue. They work together with isoleucine to promote muscle growth, provide muscle fuel, repair tissues, support blood glucose regulation and prevent catabolism, the breakdown of muscle. The BCAAs also help muscles recover after strenuous activity.

Muscle Growth

Protein is made up of carbon, hydrogen and oxygen; but its additional molecule, nitrogen, is not found in other macronutrients that play a key role in muscle synthesis. When you ingest protein, nitrogen is released into the bloodstream. It is a balance of nitrogen that promotes muscle growth. An equal balance of nitrogen means your body is excreting the same amount of protein that it's taking in, whereas a positive nitrogen balance means that you are consuming more protein than your body needs. It is this excess protein that can contribute to muscle growth.

Carbohydrate and Fat Metabolism

Your body uses nutrients found in your diet to carry out bodily functions. Carbohydrates are an important dietary component, because they are your body's preferred fuel source. Carbohydrates include fiber, sugars and starches. Valine helps your body metabolize carbohydrates and release energy for fuel usage.

Fats are another source of body fuel. Fat is produced in your liver and received from your diet. Leucine helps your body metabolize fat. This makes leucine and valine beneficial to carbohydrate and fat metabolism.

Sources

Leucine and valine are dietary necessities, since your body cannot produce either nutrient. Sources high in leucine include soybeans, lentils, beef, chicken, nuts and egg yolks. Valine is found in eggs, seaweed, seeds, fish -- especially cod -- and milk. You generally receive enough protein to meet your needs; however, because excess protein contributes to muscle growth, individuals seeking this effect generally ingest additional protein in the form of dietary supplements. Consult your doctor before taking leucine or valine supplements.