Vitamin D

Cholecalciferol (Vitamin D3)

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Functions

Deficiency

Mild

  • interferes with utilization of calcium and phosphorus in bone and teeth formation
  • irritability
  • weakness

Severe

  • rickets in young children
    • childhood deficiency disease marked especially by soft deformed bones
  • osteomalacia in adults

Characteristics

  • soluble in fats and organic solvents
  • relatively stable under refrigeration
  • stored in liver
  • precurser: UV-activated 7-dehydro-cholesterol

Good Sources

Natural

  • butter
  • egg yolks
  • oily fish
    • salmon, tuna fish, herring, sardines, mackerel, bluefish, catfish
  • oysters
  • liver
  • exposure to sunlight
    • formed in the skin

Food Quantity mcg IUs
Cheese, cheddar 1 oz 0.075 3
Egg 1 large 0.675 27
Milk, non-fat 1 cup 2.5 100
Red Salmon (canned) 1/2 cup 23.5 940
Cat Fish (cooked) 3 oz 14.25 570
Multivitamins (most brands) 1 tablet 10 400

Artificial

  • cod liver oil and fish oils
  • yeast
  • foods irradiated with ultraviolet light
  • fortified milk
  • Vitamin D2, or ergocalciferol is 25 percent less effective than Vitamin D3, or Cholecalciferol

Sun Exposure

  • In summer, as little as five minutes of sun a day on unprotected hands and face can replete the body's supply
    • Excess can be stored for later use
  • During the remainder of the year, most people need a dietary intake
    • People in the northern two-thirds of the USA make little or no vitamin D in winter

Notes

  • Randomized trials using the currently recommended intakes of 400 I.U. vitamin D a day have shown no appreciable reduction in fracture risk. In contrast, trials using 700 to 800 I.U. found less fracture incidence, with and without supplemental calcium. This change may result from both improved bone health and reduction in falls due to greater muscle strength (American Journal of Clinical Nutrition 2007).
  • A Swiss study of women in their 80s found greater leg strength and half as many falls among those who took 800 I.U. of vitamin D a day for three months along with 1,200 milligrams of calcium, compared with women who took just calcium.

Adequate Intakes (AI)

  • Males (11 yrs. and older)
    • 200 IU (5 mcg)
  • Females (11 yrs. and older)
    • 200 IU (5 mcg)
  • Pregnant females
    • 400-600 IU (10-15 mcg)
  • Lactating females
    • 400-600 IU (10-15 mcg)
  • Children
    • 400 IU (10 mcg)
  • Infants
    • 400 IU (10 mcg)
  • Sufficient data to set RDA are unavailable

Tolerable Upper Intake Levels (UL)

  • Adults (19 to 50 yrs)
    • 2000 IU (50 mcg)
    • Bruce W. Hollis
      • researcher and pediatric nutritionist at the Medical University of South Carolina in Charleston
      • suggests the current top level of 2,000 I.U. is based on shaky evidence
      • cites pregnant women taking 4,000 I.U. a day, and nursing women taking 6,000 I.U. a day, with no adverse effects
    • Other experts suggest high vitamin D levels (above 800 I.U.) with calcium may raise the risk of kidney stones in susceptible people

Intakes above UL may lead to negative health consequences.

Supplementation

  • May be necessary for vegetarians, elderly, those who don't drink fortified milk, or get sun exposure.
  • Older people make less vitamin D in their skin and are less able to convert it into the hormone that the body uses.
  • Toxic in high doses.


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