Vitamin D - calciferol

Vitamin D is a fat-soluble vitamin. In humans, vitamin D can be ingested as cholecalciferol (vitamin D3) or ergocalciferol (vitamin D2). The vitamin can also be synthesized in the body from cholesterol when sun exposure is adequate (hence its nickname, the "sunshine vitamin").

vitamin D is important for your bones The liver and kidneys modify the vitamin to the biologically active form (calcitriol), which circulates in the blood as a hormone regulating the concentration of calcium and phosphate in the bloodstream and promoting the healthy growth and remodeling of bone.

Vitamin D assists in the proliferation and differentiation of cells and affects neuromuscular function and inflammation.

Sources

Relatively few foods contain vitamin D. Some fish, such as salmon, tuna and mackerel, as well as fish liver oils are the best sources. Some vitamin D is also present in beef liver, cheese and egg yolks.

In the Western world most of the vitamin D in the food comes from fortified foods - where vitamin D is artificially added. Vitamin D is often added to milk, many breakfast cereals and to some brands of orange juice, yoghurt, margarine, and soy beverages. Here is a list of foods having the highest content of vitamin D.

Daily intake

The recommended daily intake is 600 IU (15 micrograms) for children and adults 9–70 years, 800 IU (20 micrograms) for adults > 70 years, and 600 IU (20 micrograms) for pregnant and lactating women.

The tolerable upper limit is 4000 IU (100 micrograms) per day for ages 9–71+ years (including pregnant or lactating women).

Deficiency

A diet deficient in vitamin D causes rickets in children and osteomalacia in adults.

The problem in both diseases is a softening of the bones leading to impeded growth, deformity, bone fragility and muscular weakness and pain. In the developed world, these diseases are rare.

Excess

In healthy adults, sustained intake of more than 1250 micrograms/day (50,000 IU) can produce toxicity after several months.

Vitamin D overdose causes hypercalcemia associated with anorexia, nausea, vomiting, polyuria, polydipsia, weakness, insomnia, nervousness, pruritus, and, ultimately, renal failure.

References: 1 , 2 , 3 , 4