Autism and autistic spectrum disorder are chronic neuro-developmental disorders characterized by social and language impairments and stereotyped, repetitive patterns of behavior. The etiology of autism remains unknown; however, a strong genetic component has been detected and environmental factors may also be involved in their etiologies. In the current study, we reviewed evidence for the presence of prenatal and perinatal factors, gastrointestinal factors, food allergies, metabolic and heavy metal factors, and other nutritional factors that may represent risk factors for the development of autism and autistic spectrum disorder.