Abstract
Vitamin D (a fat-soluble vitamin) is synthesized by humans and plants when they are placed under the influence of sunlight. Two major forms of vitamin D are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). People can get vitamin D2 from plants and vitamin D3 from animal sources (mainly fatty fish). Most vitamin D is obtained through sunlight exposure. Vitamin D can also be received from fortified foods and dietary supplements made as medicine. Vitamin D deficiency (VDD) is an important public health problem because the low level of vitamin D in the blood is a risk factor for some severe diseases, such as cancer, heart disease, fractures and falls and etc. Vitamin D is also an important factor in the prevention and treatment of some skeletal and nonskeletal diseases. Skeletal diseases include rickets in children, osteoporosis, osteomalacia (known with bone pain) and bone loss in people with hyperparathyroidism. Nonskeletal diseases include high blood pressure and high cholesterol, diabetes, obesity, rheumatoid arthritis, multiple sclerosis, premenstrual syndrome (PMS), autoimmune diseases and cancers. Because there are many obstacles to sunshine exposure, including usage of sunscreen, hats, and other skin covers, decreased hours of sun exposure during aging and the winter; therefore, we can see a prompt increase in the number of people with VDD. Since the number of people with VDD is increasing, the research on this vitamin and its importance in public health and the prevention of severe diseases is very important. In this review, we summarize the association between VDD and some important diseases, and understand clinical benefits of vitamin D.