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Vitamin D Simplified

Vitamin D, the sunlight vitamin. How do we get it, what does it do, and what happens if we get too much or too little?

Nutrition For the Curious Public

vitamin d

By Stefanie Schwartz MS, RD, CDN, Richard Strongwater MD, and Stuart M Caplen MD

Cholecalciferol (Vitamin D3) is produced in the body when ultraviolet rays from the sun hit the skin and trigger vitamin D synthesis from cholesterol.

Vitamin D is actually a group of fat-soluble vitamins but only two, vitamin D2 also called ergocalciferol, and vitamin D3 also known as cholecalciferol are present in humans. Vitamin D4 is present in certain mushrooms and the benefits of it in humans is uncertain.

forms of vitamin D - D2, d3, d4, Calcitriol

Sources of Vitamin D

Cholecalciferol (Vitamin D3) is produced in the body when ultraviolet rays from the sun hit the skin and trigger vitamin-D synthesis from cholesterol. The liver then converts vitamin D3 to calcidiol, and then the kidneys convert calcidiol to the active form, calcitriol.

In food, Vitamin D2 is generally ...

Read the full article for more about Vitamin D:

Risk Factors for Vitamin D Deficiency

Why Vitamin D?

Vitamin D Deficiency Defined

Too Much Vitamin D ?

Current Recommendations

Read the full Vitamin D Simplified article on


For more information regarding recommended Vitamin D levels, Vitamin D supplementation, deficiencies and more formal indications for treatment check out our FibonacciCOMPENDIUM on

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