Vitamin D Functions and Dosage - Food sources and Deficiency symptoms and causes of Vitamin D


Vitamin D is a steroid hormone that functions to regulate specific gene expression following interaction with its intracellular receptor. The biologically active form of the hormone is 1,25-dihydroxy vitamin D 3 (1,25-(OH) 2 D 3). Calcitriol functions primarily to regulate calcium and phosphorous homeostasis.

Food Sources of Vitamin D

Vitamin D is present in fatty fish like kipper, sardines, salmon, tuna and mackerel, liver, egg yolk and butter. Smaller amounts are also present in dark leafy vegetables.

Functions of Vitamin D

Vitamin D promotes the body's absorption of calcium, which is essential for the normal development and maintenance of healthy teeth and bones. Calcium is also important to nerve cells, including the brain. Vitamin D also helps maintain adequate blood levels of calcium and phosphorus. The form of vitamin D that we get from food or supplements is not fully active. It requires conversion by the liver, and then by the kidneys, before it becomes fully active. This is why people with liver or kidney disorders are at a higher risk for osteoporosis. When the skin is exposed to the sun's ultraviolet rays, a cholesterol compound in the skin is transformed into a precursor of vitamin D. Exposing the face and arms to the sun for fifte en minutes three times a week is an effective way to ensure adequate amounts of vitamin D in the body.


The current recommended intake of vitamin D is 5 micrograms up to age 50, 10 micrograms between the ages of 51 and 70, and 15 micrograms after age 70. Very few foods naturally contain vitamin D. Good sources include dairy products and breakfast cereals (which are fortified with vitamin D), and fatty fish such as salmon and tuna. For most people, the best way to get the recommended daily intake is by taking a multivitamin.

What are the deficiency symptoms of vitamin D?

The main symptom of vitamin D deficiency in children is rickets and in adults is osteomalacia. Other symptoms are tooth decay, softening of bones, improper healing of fractures, lack of vigor, muscular weakness, inadequate absorption of calcium, retention of phosphorous in the kidneys. Rickets is characterized improper mineralization during the development of the bones resulting in soft bones. Osteomalacia is characterized by demineralization of previously formed bone leading to increased softness and susceptibility to fracture.

Overdosage signs of vitamin D

Overdosage Symptoms may include High blood pressure, Irregular heartbeat, Nausea, Weight loss, Seizures, Abdominal pain, Appetite loss, Mental-and physical-growth retardation, Premature hardening of arteries, Kidney damage. Excessive doses of vitamin D can result in increased calcium absorption from the intestinal tract. This may cause increased calcium resorption from the bones, leading to elevated levels of calcium in the blood. Elevated blood calcium may then cause calcium deposition in soft tissues such as the heart and lungs. This can reduce their ability to function.


Drugs or Nutrients that decrease its absorption or levels in the body: Anticonvulsivants (Barbiturates, Carbamazepine, Fosphenytoin) , Bile acid sequestrants (Cholestyramine, Colestipol), Corticosteroids, H-2 receptor antagonists (include Cimetidine), Isoniazid, Mineral Oil ,Rifampicin, Orlistat.

How to Store the Vitamin D?

Heat and/or moisture may alter the vitamin. Refrigeration is recommended.

Vitamin D Deficiency



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