Autism Spectrum Disorder: Does Diet Have An Impact?

The search to identify metabolic defects leading to autistic behaviors that might respond to dietary treatment has resulted in several possibilities. The role of branched chain amino acids in improving ASD symptoms in a select group of patients with a mutation in the BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) gene was investigated. In this case, the disorder results in neurological symptoms due to an unbalanced level of amino acids entering the brain, especially several which are metabolized to neurotransmitters [8]. Another known genetic polymorphism occurs in the gene, TMLHE (trimethyllysine hydroxylase, epsilon) which is responsible for producing the first enzyme leading to carnitine synthesis. Deficient blood levels of carnitine lead to reduced transport of carnitine into the brain, with abnormal synaptic development [9]. Other possible dietary supplements being evaluated are those that are involved in enhancing onecarbon metabolism. Inadequate intake of vitamins including a derivative of folic acid (5-methyl THF), choline and pyridoxine as well as several amino acids (methionine, serine and glycine) that contribute to the functioning of the “folate cycle” and therefore the epigenetic process of DNA methylation, may be involved in the development of ASD. Recently, it has also been shown that lower than normal levels of these nutrients are found in the blood of both ASD children and their parents. The most intriguing evidence of dietary adequacy of nutrients contributing to the “folate cycle” and susceptibility to ASD comes from dietary studies on mothers with and without the MTHFR (methyl tetrahydrofolate reductase) 677C>T polymorphism. Mothers who had this polymorphism had a greater risk of having a child with ASD when folic acid intake was low prior to and during the early part of pregnancy [10]. Other than the neurological defects which occur with ASD,