vitamin d

Vitamin D, also called calciferol, is a fat soluble vitamin that has properties of both a vitamin and a hormone. It is required for the absorption and utilization of calcium and phosphorus. Vitamin D is necessary for growth and is extremely important for the normal growth and development of bones and teeth in children. It protects agains muscle weakness and is involved in regulation of the heartbeat.

Calcium is a mineral in your body that makes up your bones and keeps them strong. Phosphorus is a mineral that helps maintain good teeth and bones and keep muscles and nerves working properly. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. Without vitamin D, bones can become thin, brittle and soft. Vitamin D prevents rickets in children and osteomalacia in adults. Rickets causes skeletal deformities. Osteomalacia causes muscular weakness and weak bones.

Vitamin D is found in food, but also can be made in your body after exposure to ultraviolet rays from the sun. There are several different forms of vitamin D. Each form has a different activity.

Types of vitamin D?

There are several forms of vitamin D:

  • Vitamin D2
    • Also called ergocalciferol, this is obtained from food sources
    • 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 diseases have increased risk of developing osteoporosis
  • Vitamin D3
    • The most natural form, also called cholecalciferol, is synthesized in the skin in response to exposure to the sun’s UV rays
  • Vitamin D5
    • Synthetic vitamin D

What are the sources of vitamin D?

The major sources of vitamin D are food and exposure to sunlight.

The major food sources are:

  • Fortified foods are the major dietary sources of vitamin
    • Milk in the United States is fortified with 10 micrograms (400 IU) of vitamin D per quart
  • Fatty fish and fish oils
  • Dairy products
  • Eggs
  • Exposure to sunlight is an important source of vitamin D. Ultraviolet (UV) rays from sunlight trigger vitamin D synthesis in the skin

Vitamin D deficiency

If a person is deficient in vitamin D, diseases such as rickets and osteomalacia may develop. A deficiency of vitamin D can occur when dietary intake of vitamin D is inadequate, when there is limited exposure to sunlight, when the kidney cannot convert vitamin D to its active form, or when someone cannot adequately absorb vitamin D from the gastrointestinal tract.

The classic vitamin D deficiency diseases are rickets and osteomalacia. In children, vitamin D deficiency causes rickets. In adults, vitamin D deficiency can lead to osteomalacia.

Who is at risk of vitamin D deficiency?

Approximately 40% of Americans do not receive adequate amounts of vitamin D from their diets. Americans over the age of 50 man have an increased risk of vitamin D deficiency. This occurs because the ability of skin to convert vitamin D into its active form decreases as we grow older. Also, the kidneys, which help, convert vitamin D to its active form, sometimes does not work as well in older people.

Individuals who have reduced ability to absorb dietary fat (fat malabsorption) may need extra vitamin D because it is a fat soluble vitamin. Crohn’s Disease, cystic fibrosis, pancreatic enzyme deficiency and liver disease may reduce a person’s ability to absorb dietary fat. Some of the common symptoms of fat malabsorption are diarrhea and greasy stools.

Too much vitamin D?

Too much vitamin D (10,000 IU) can cause nausea, vomiting, poor appetite, constipation, weakness, bone pain and weight loss. Too much vitamin D can also cause kidney stones or calcification of soft tissue. It can also raise blood levels of calcium. High blood levels of calcium causes confusion and heart rhythm abnormalities.

Vitamin D from a tanning bed

Exposure to UVB radiation can increase vitamin D levels. However receiving vitamin D from tanning beds is not recommended. Increased levels of vitamin D obtained via tanning bed exposures are heavily outweighed by the risks of using a tanning bed. Tanning beds emit high levels of UVA, which can cause melanoma but do not contribute to vitamin D production.