Vitamin D, sometimes known as the sunshine vitamin, has been the subject of great debate. Perhaps the two most important questions are: how much is too much and what is an “optimal” level? The Vitamin D Council considers vitamin D to be essential for supporting bone health, cancer prevention, prevention of the common cold, and reduction of depression, as well as a host of other reasons. Clinical studies have shown each of these conditions to be associated with insufficient vitamin D levels.
The Vitamin D Council recommends that the blood level of 25(OH) D (the “official” measurement of vitamin D) needs to be at least 30 ng/mL in order to be considered sufficient. The 2001–2002 National Health and Nutrition Examination Survey (NHANES) found that approximately 10 percent of the population has concentrations of 25(OH)D less than 11 ng/mL, with higher 25(OH)D concentrations found in non-Hispanic whites and lower levels found in non-Hispanic blacks. Vitamin D levels are lower during winter months, especially for those with little sun exposure, the elderly, and in those with darker skin.
So just how do you know if your vitamin D is sufficient?
Check vitamin D levels
The main circulating form of vitamin D in humans is total 25(OH) D, which is considered the best assessment of vitamin D status, derived from both sun exposure and diet. In addition to providing the total 25(OH)D level, the Metametrix Vitamin D Assay now distinguishes between natural cholecalciferol (vitamin D3) and synthesized ergocalciferol (vitamin D2). Vitamin D3 is synthesized in the skin by the sun, whereas D2 is derived from fungal sources and is used in fortified foods and most supplements. Some experts believe that the only form that should be used is vitamin D3 because the majority of clinical research supports the greater effectiveness of vitamin D3 in raising and maintaining 25(OH) D levels for a variety of reasons.[2,3]
What is considered optimal?
There is no consensus on what is truly considered either a deficient or a toxic vitamin D level. A 2011 Endocrine Society Clinical Practice Guideline defined levels for insufficiency and sufficiency, and the Vitamin D council concurs with the suggested appropriate optimal and upper limit levels as follows:[4,5]
- < 20 ng/ml to be deficiency
- 21–29 ng/ml to be insufficiency
- 30–100 ng/ml to be sufficiency
- 100 ng/mL as an upper limit
The RDA suggests 1000–4000 IU daily, with 3000 IU/day required to ensure most people have 25(OH) D levels greater than 35 ng/mL. The Vitamin D Council recommends 5000 IU daily for adults to maintain minimal optimal levels. Ten to fifteen minutes of sun exposure provides at least 10,000 IU of vitamin D in individuals with fair skin. In the absence of sun exposure, there are many natural food sources of vitamin D (salmon, tuna, egg yolk), as well as fortified food sources such as milk and orange juice (which are fortified with a minimum of 100 IU of vitamin D). Supplemental vitamin D3 is also available in capsules up to 5,000 IU.
While we are on the tail end of winter, now makes a perfect time to order the improved Metametrix Vitamin D Assay to determine your patient’s vitamin D levels.
Further information may be found the Metametrix Learning Center:
~ Christie Egeston, MS
- Wagner CL, Greer FR. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics. Nov 2008;122(5):1142-1152.
- Armas L, Hollis, B.W., Heaney, R. Vitamin D2 is much less effective than vitamin D3 in humans. The Journal of Clinical Endocrinology & Metabolism. 2006;89(11):5387-5391.
- Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. The American journal of clinical nutrition. Oct 2006;84(4):694-697.
- Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Altern Med Rev. Mar 2008;13(1):6-20.
- Holick MF. Vitamin D deficiency. N Engl J Med. Jul 19 2007;357(3):266-281.
- Heaney RP, Davies KM, Chen TC, Holick MF, Barger-Lux MJ. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. The American journal of clinical nutrition. Jan 2003;77(1):204-210.