Vitamins are essential parts of nutrition, required in small quantities for normal metabolism. These are not produced in human bodies and their deficiency can cause diseases. Vitamin D however, is an exception as it can be produced in the human skin.
Vitamin D :
Rickets in children and osteomalacia in adults are bone diseases due to deficiency of Vitamin D. Rickets was 1st described in 1600 but the cause of the disease discovered later.
Vit D is also called Calciferol. Vitamin D2 from plants is called ergosterol while the vitamin found in animal sources is Vitamin D3.
Vitamin D is found in fatty fish, cod liver, eggs etc. Milk is, however, a poor source. Milk and vegetable oils in some countries may be fortified with Vitamin D. In human beings, Provitamin D in the skin is converted to Cholecalciferol. This then is converted 1st in the liver and then in the kidneys to its active form (1,25 OHD).
Requirements of Vitamin D:
About 600 units of Vit D are required from age 1 yr to 70 yrs. From 71st year 800 units may be required.
Though it can be produced in the skin from sunlight, various factors influence its production. These are
Slants of sunrays, (winter or summer)
Clothing, use of sun lotions
Pigmentation in the skin (Africans produce less vitamin D then Indians which produce less than white children. In terms of time a white child without clothes, ½ hr of sunlight in a week may be enough. In Africa, three times this exposure may be required.
Vitamin D Deficiency:
Levels of Vitamin D of about 20 are usually sufficient. Adolescents with high growth needs may be more prone to deficiency.
Causes of Vitamin D deficiency:
Commonest is lack of exposure to sunlight. Other causes may be intestinal diseases which prevent fat absorption as this vitamin is fat soluble. The lack of activation can occur in liver and kidney diseases.
Actions of Vitamin D
It takes an important part in the regulation of calcium and phosphorus metabolism. Lack of Vitamin D causes low calcium level, parathormone increases and phosphorus is excreted by kidneys. This results in changes in growing bone in children (Rickets) and in already formed bones in adults( Osteomalacia).
The bones have less calcium, are weaker, more prone to fractures and in childhood, deformed bones are common. Rickets can lead to stunted growth, height remains less, bones may be bent or broken etc. These changes can be found by clinical examination, X Rays, and bone density. The diagnosis can be made by Vitamin D levels of total Vitamin D or its activated metabolites.
Treatment is done by providing Vitamin D supplementation. In rare varieties of Rickets due to genetic causes, expert help is needed for diagnosis and therapy.