Vitamin D

Vitamin D

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At a Glance

Vitamin D is actually a group of prohormones, which have a number of important jobs in the body. These include helping the body absorb calcium, helping with immune system function, regulating glucose tolerance, and helping to regulate blood pressure. Vitamin D is the only vitamin that can be obtained through the sun. You can also get vitamin D by eating egg yolks and oily fishes such as salmon, sardines, and mackerel, or through vitamin D fortified foods.

Overview

Vitamin D, a fat soluble vitamin, is the only vitamin that can be obtained through the sun.

Vitamin D is really a group of prohormones. Vitamin D must be metabolized to its biologically active form in the body. After it is eaten or synthesized in the skin, it enters the bloodstream for transport to the liver. There it is hydroxylated to form 25 hydroxyvitamin D. In the kidney, a second hydroxylation results in calciferol, or 1,25 dihydroxyvitamin D—the most potent form.

Importance

Vitamin D has many functions in the body including:

  • Gene transcription modulation
  • Increasing calcium uptake and reabsorption, maintaining serum calcium levels
  • Cell differentiation
  • Immune system function
  • Regulating glucose tolerance
  • Helping regulate the renin-angiotensin cascade and blood pressure.

Food Sources

Vitamin D can be found in several foods including:

Deficiencies

Common symptoms and resulting conditions of vitamin D deficiency in children include:

  • Rickets
  • Deformed bones
  • Retarded growth
  • Soft teeth.

Common symptoms and resulting conditions of vitamin D deficiency in adults include:

  • Osteomalacia
  • Softened bones
  • Spontaneous fractures
  • Tooth decay.

However, your individual response could be different. If you suspect a health problem or deficiency in certain nutrients, please see your primary health care provider (doctor, naturopath, etc). They can help unravel the complexity of your physiology.

Note: Those most at risk for deficiency include infants, elderly, dark skinned individuals, those with minimal sun exposure, fat malabsorption syndromes, inflammatory bowel diseases, kidney failure, and seizure disorders.

Excess/Toxicity

Common symptoms of vitamin D excess/toxicity include:

  • Elevated blood calcium levels
  • Loss of appetite
  • Nausea
  • Vomiting
  • Excessive thirst
  • Excessive urination
  • Itching
  • Muscle weakness
  • Joint pain
  • Disorientation
  • Calcification of soft tissue.

However, your individual response could be different. If you suspect a health problem or an excess of certain nutrients, please see your primary health care provider (doctor, naturopath, etc). They can help unravel the complexity of your physiology.

Note: hypervitaminosis is not a result of sun exposure but from chronic supplementation. Only excessive supplement use will cause the symptoms above.

Recipe

For recipes rich in vitamin D, check out any of the Encyclopedia of Food entries for food items listed above.

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At a Glance

Vitamin D is actually a group of prohormones, which have a number of important jobs in the body. These include helping the body absorb calcium, helping with immune system function, regulating glucose tolerance, and helping to regulate blood pressure. Vitamin D is the only vitamin that can be obtained through the sun. You can also get vitamin D by eating egg yolks and oily fishes such as salmon, sardines, and mackerel, or through vitamin D fortified foods.