June 10, 2015

Understanding the Different Forms of Vitamin D

By cancerconnect

Long known as an important factor in bone health, a quickly growing body of evidence now also shows that vitamin D may help lower the risk of cancer, heart disease, and even premature death.1,2 Vitamin D exists in several forms. A simple guide to these different types will help you better understand this vitamin’s potential health benefits.

It’s easy to get overwhelmed by an alphabet soup of scientific notation when you begin to delve into the topic of vitamin D. But it’s really not as complicated as it may seem. Here’s a quick guide to the different forms of the vitamin and how it likely helps protect against cancer.

  • Vitamin D3 and D2. Forms of the vitamin produced in the skin and found in supplements and food.
  • 25(OH)D (calcidiol). Vitamin D3 and D2 get converted to this prohormone form of the vitamin, which is the major form found in the blood. 25(OH)D is most often used to determine someone’s vitamin D level.
  • 1,25(OH)2D (calcitriol). One final conversion creates this “active” hormone form of the vitamin, blood levels of which rarely change, even as levels of other types of vitamin D go up and down.  1,25(OH)2D helps influence bone metabolism and promote healthy cell growth, which is the likely reason the vitamin helps lower cancer risk and even prolong survival.



1.  Heaney RP. Vitamin D in health and disease. Clin J Am Soc Nephrol. Sep 2008;3(5):1535-1541.

2.  Melamed ML, Michos ED, Post W, Astor B. 25-hydroxyvitamin D levels and the risk of mortality in the general population. Arch Intern Med. Aug 11 2008;168(15):1629-1637.

Tags: Nutritional Know-How