Functional food can be defined as a food that delivers a health benefit beyond basic nutrition and makes a claim about this benefit. Functional foods can be whole foods or foods that naturally contain or have been fortified with nutrients and/or bioactive substances that provide a specific benefit to health. Epidemiological studies randomized clinical trials carried out in different countries have demonstrated numerous health effects related to functional food consumption, such as reduction of cancer risk, improvement of heart health, stimulation of immune system, decrease of menopause symptoms, improvement of gastrointestinal health, maintenance of urinary tract health, anti-inflammatory effects, reduction of blood pressure, maintenance of vision, antibacterial and anti-viral activities, reductions osteoporosis and anti-obese effect. Therefore, this review article will give an idea of functional foods from the chemical and nutritional point of view. Also, the effect of some functional foods such artichoke, milk thistle, turmeric and gum arabic on the prevention and/or treatment of some diseases will be also dicussed.