The Mayo Medical Laboratories Difference

Vitamin D is vital for strong bones. It also has important, emerging roles in immune function and cancer prevention. Deficiencies at any stage of life can have devastating consequences. Similarly, vitamin D toxicity resulting from overmedication can cause serious hypercalcemia. Vitamin D consists of two bioequivalent forms:

• Vitamin D2, which is obtained from vegetable sources (dietary sources, supplements); and
• Vitamin D3, which is derived from both endogenous (synthesized from cholesterol through sun exposure) and exogenous (animal diet) sources.

Until recently, vitamin D replacement in the United States consisted exclusively of 25-hydroxy-vitamin D2. During the last 1-2 years this has started to change, with an increasing proportion of 25-hydroxy-vitamin D3 being used, in particular in high dose prescription formulations.

Vitamin D deficiency is more common than previously believed, especially among adolescents, women, and the elderly. For example, studies have shown that more than 50% of the institutionalized elderly and an equal proportion of women of any age undergoing treatment for osteoporosis have inadequate levels of vitamin D.¹ While treatment with vitamin supplementation is easy and inexpensive, many affected individuals go undiagnosed and untreated.

The total 25-hydroxyvitamin D (25OH Vit D) level (the sum of 25OH vitamin D2 and 25OH vitamin D3) is the appropriate indicator of vitamin D body stores. Although there is no universal consensus about a treatment cut point, studies suggest 25 to 35 ng/mL as the minimal concentration of 25OH Vit D needed to avoid the adverse effects of deficiency.^2,3,4 By contrast, population reference ranges do not correspond with healthy ranges. In northern latitude locations in particular, one third of the population may have levels below 25 ng/mL at the end of winter.