Vitamin D Monica Durham Rahmina Mutlib
Vitamin 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
Functions • 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.
Functions • 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
Functions • 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
Absorption, Distribution, Metabolism • 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
Excretion • Excreted in bile • Metabolized to water soluble metabolites and then excreted in urine as well
Sources • 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
Deficiency • 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
Risk Factors • 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
Diseases • Rickets/Osteomalacia • caused by lack of vitamin D, calcium, or phosphate, which leads to softening and weakening of the bones
Vitamin D vs. Autism • 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.
Vitamin D vs. Heart Disease • 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
Toxicity • 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