Isoleucine is a essential branched chain amino acid found abundently in most foods. Isoleucine is found in especially high amounts in meats, fish, cheese, most seeds and nuts, eggs, chickens and lentils.
In the human body Isoleucine is concentrated in the muscle tissues. Isoleucine is necessary for hemoglobin formation and in stabilizing and regulating blood sugar and energy levels. A deficiency of isoleucine can produce symptoms similar to those of hypoglycemia. It has been identified as one of a group of amino acids deficient in amino acid profiles run on mentally and physically ill patients. Isoleucine is frequently deficient in the elderly, and may contribute to muscle wasting, twitching and tremors.
The branched chain amino acids (BCAAs) are Isoleucine, Leucine and Valine. BCAAs are popular with body builders looking to restore muscle mass traumatized from excessive overtraining. BCAAs are also used to treat injuries and physical stress conditions , such as surgery and liver disease. The ability of these amino acids to help in abnormal conditions does not imply that they will help in healthy individuals, and no studies indicate that extra intake will help in muscle building.
Since the body cannot make this amino acid from other sources, maintaining sufficient amounts in the diet IS important. Jeffery Bland, author of Medical Applications of Clinical Nutrition, gives the range of isoleucine requirement in normal adults as being between 250 and 700 milligrams daily. The isoleucine content of animal protein is 42 milligrams per gram of protein.