Vitamin D and Ultraviolet Radiation

Vitamin D has several different forms, about 5 in all.
They are actually a group of fat-soluble ‘prohormones’ (precursors to hormones).

The 2 main forms of vitamin D important for humans are:

• D2 (ergocalciferol) = synthesized by plants
• D3 (cholecalciferol) = synthesized by our skin when exposed to ultraviolet rays, specifically the UV-B rays, in sunlight. (Foods are often fortified with both of these forms, D2 and/or D3.)

  

  
  -- SOURCES --
  When exposed to sunlight, skin performs the very important function of producing this vitamin!

  If sun exposure is limited, other sources can be used to supplement such as dietary supplements and food sources. Rich food sources include salmon, tuna, fish liver oils plus some in cheese and egg yolks.

  
  
  
  -- PURPOSE --
  - Maintains calcium and phosphorus blood levels.
  - Helps in calcium absorption to maintain and form strong bones
  - Other bodily functions such as affecting parathyroid secretion, the immune system, and more...

  
  -- HOW MUCH SUN EXPOSURE IS REQUIRED?
  Sources vary a bit.

  

  One recommendation says approximately 10-15 minutes of time in the midday sun, 2 to 3 times per week to the face, arms, head, or back without sunscreen. Another suggested 5-30 minutes midday a minimum of twice a week without sunscreen to same body areas.

  However, for those with light skin, 15-30 minutes of midday sun 5-6 times a week to these areas of the body (no sunscreen) may be sufficient to provide enough of the vitamin. Use common sense and don't get a sunburn!

  
  -- FACTORS THAT INFLUENCE how much is made in the skin include:
  - cloud cover
  - smog
  - time of day
  - earth location
  - seasons
  - sunscreen use
  - amount of melanin in the skin

  
  For instance, it depends on the season of the year and how close you live to the equator where sun rays are strongest. Also, people with higher melanin content in their skin need more sunlight time to produce an equal amount as someone with less melanin in their skin.

  Some experts advise daily supplementation to help when sunshine levels are too low, as in northernmost regions in fall and winter.

  (Sources: Wikipedia and Hallelujah Acres Health News and others )

  It's a matter of balance and common sense when in the sun!

  
  

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  Go to "Skin Anatomy" | See "Skin Cancer" | Go to "Sunburn"

  Go to "UV Radiation" | See "Freckles & Melanin"

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