Addiction to the illicit and prescribed use of opiate is an alarming public health issue. Studies on addictive disorders have demonstrated severe nutritional deficiencies in opiate abusers with behavioral, physiological and cognitive symptoms. Opiate addiction is also link with a significant number of diseases including Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV) and other blood borne diseases generally stem from the use of needles to inject heroin. The use of medication assisted treatment for opioid addicts in combination with behavioural therapies has been considered as a highly effective treatment. Methadone is a long-lasting mu-opioid agonist and a pharmacological tool which attenuates withdrawal symptoms effectively replacement therapies. This review article aims to explain opiate addiction mechanisms, epidemiology and disease burden with emphasis on dietary and nutritional status of opiate dependent patients in methadone maintenance therapy.