Considerable attention has been focused on the development of strategies to treat patients with inherited metabolic defects. Attempts have been made to decrease the concentration of accumulated products by dietary restriction, chelation, and administration of appropriate medicines to correct the metabolic block or supplementation with a normal product. Dietary intake of phenylalanine can be restricted or rather controlled with a synthetic diet rich in vitamins, minerals, fats, carbohydrates, fruits, vegetables and certain other foods. The affected individuals have to be constantly monitored for the levels of the chemical in their body. The diet plan is very effective when started within the first two months after birth. Hyperactive and difficult babies become more alert and responsive and usually develop normal or near-normal intelligence. It is very important to identify the disorder before brain damage occurs.