V ITAMIN D Monica Durham Rahmina Mutlib

V ITAMIN D Vitamin D is a fat soluble vitamin Synthesized by the body after exposure to UV rays or obtained from food sources It is biologically inactive By increasing calcium absorption, vitamin D helps to form and maintain strong bones

F UNCTIONS Cell differentiation inhibits proliferation and stimulates the normal differentiation of cells Immunity The inactive form of vitamin D aids in the formation of active vitamin D which enhances immunity and inhibits the development of autoimmune disease.

F UNCTIONS Calcium balance With decreased dietary calcium, PTH is secreted and causes increased production of calcitriol, a hormone Calcitriol restores normal calcium levels by increased absorption of dietary calcium, increased mobilization of calcium from bone, and increased reabsorption from kidneys

F UNCTIONS Heart disease Renin, important in regulation of blood pressure and heart health, is associated with vitamin D levels Maintaining normal phosphorus levels Bone cannot be properly mineralized without phosphorus

A BSORPTION, D ISTRIBUTION, M ETABOLISM Absorption Vitamin D is absorbed from the small intestine as bile salt Distribution Stored in adipose tissue Metabolism Transported to the liver, then kidneys, where it is activated

E XCRETION Excreted in bile Metabolized to water soluble metabolites and then excreted in urine as well

S OURCES Fortified foods Milk, cheese, yogurt, orange juice Ready to eat cereals Sun exposure Rays from the sun trigger synthesis in the skin Factors Season Altitude Time of day Cloud cover (eg. Smog) Sunscreen

D EFICIENCY During vitamin D deficiency, calcium absorption cannot be increased to meet body's needs Therefore, calcium is taken from bones to maintain normal serum levels

R ISK F ACTORS Higher melanin content (darker skin) Breast-fed infants Elderly Body covering/use of sunscreen Fat malabsorption syndrome Obesity Inadequate dietary intake Increased excretion Genetic susceptibility

D ISEASES Rickets/Osteomalacia caused by lack of vitamin D, calcium, or phosphate, which leads to softening and weakening of the bones

V ITAMIN D VS. A UTISM An increased prevalence of autism over the last years corresponds with increasing medical advice to avoid the sun, advice that has probably lowered vitamin D levels and would greatly lower activated vitamin D (calcitriol) levels in developing brains. Autism is common in areas of impaired UVB penetration such as urban areas, areas with high air pollution, and areas of high precipitation. Autism is more common in dark-skinned persons with vitamin D deficiency One study showed children with vitamin D deficient rickets have several autistic markers that apparently disappear with high-dose vitamin D treatment.

V ITAMIN D VS. H EART D ISEASE Vitamin D deficiency was evident among individuals with high blood pressure There was a 62 % higher risk of a cardiovascular event in participants with low levels of vitamin D compared to those with higher levels Participants with high blood pressure and low vitamin D levels had two times the risk of cardiovascular disease

T OXICITY Toxic level: 40,000 IU/day for 1-4 month old; 50,000 IU/day for adults for several months Symptoms Nausea, vomiting, poor appetite, constipation, weakness, weight loss Increased blood levels of calcium result in mental confusion Heart rhythm abnormalities

R ECOMMENDATIONS Age GroupRecommended Pediatrics/adolescents IU IU IU IU