VITAMIN DMonica 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

RECOMMENDATIONS

Age Group Recommended

Pediatrics/adolescents 200-400 IU

19-50 200 IU

51-70 400 IU

71+ 600 IU