has a review.

Here are the highlights.

2 forms of vitamin D

  • Vitamin D refers to two biologically inactive precursors.
    • D2: Also known as ergocalciferol.
    • D3: Also known as cholecalciferol, which is produced in the skin on exposure to UVB radiation and is more bioactive than D2
  • Both D3 and D2 precursors are metabolized in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D) — the non-active ‘storage’ form — and 1,25-dihydroxyvitamin D (1,25(OH)2D) — the biologically active form.
  • While our bodies manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all.
    • Actually, the levels can be low along the equator too.
  • As a result, dietary supplements and fortified foods are seen by many as the best way to raise intake of vitamin D.

The bottom line?

Science supports maintaining adequate levels. Vitamin D deficiency in adults reported to precipitate or exacerbate the following conditions.

  • Osteopenia
  • Osteoporosis
  • Muscle weakness
  • Fractures
  • Autoimmune diseases
  • Infectious diseases
  • Cardiovascular diseases

There’s also evidence that vitamin D may reduce the incidence of several types of cancer and type-1 diabetes.

4/1/10 21:17 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.