Vitamin D and Obesity: Is There A Connection and Greater Need?
As discussed in my recent post on cholesterol numbers, I've had routine laboratory/bloodwork done and subsequently visited each of my main doctors (neurologist, rheumatologist, and internist) in February and March. One of the test results which is of concern is a low vitamin D serum level of 36 ng/mL.
What is Vitamin D?
Vitamin D is not actually a vitamin at all. It is a hormone precursor found in two forms: (1) ergocalciferol (vitamin D2) which is present in plants and some fish; and (2) cholecalciferol (vitamin D3) which is formed when sunlight containing ultraviolet light (UVB) hits bare skin. Enormous quantities of cholecalciferol, on average 20,000 units, is rapidly made in the skin if:
- the sun is high in the sky which occurs at midday (10AM-3PM), in the summer months, and at higher altitudes
- your skin is not covered by clothes or sunblock (simply exposing the face and hands is not enough)
- you stay in the sun until your skin just begins to turn pink, but not red (which takes longer for individuals who have more skin pigmentation)
- you are not behind glass (as glass blocks UVB, preventing vitamin D from being made)
How are Vitamin D levels tested and measured?
Levels of circulating vitamin D in the blood can be tested at the same time other blood work is completed. When requesting to have your vitamin D levels checked, it is important to ask for the 25(OH)D(3) or 25-hydroxyvitamin D test which is necessary to detect true deficiency.
Knowing what serum level is desirable can be difficult for two reasons: (1) the recommendations have changed dramatically over time; and (2) there are two different measuring systems referenced in the literature.
nanograms per millilitre (ng/mL) or nanomoles per litre (nmol/L)
For simplicity, here is a chart which summarizes the current recommendations:
25(OH)D Levels and Health Implications
In September 2008, I measured severely deficient in vitamin D at 7.8 ng/mL. Last month's results came back at 36 ng/mL which is "sufficient." Good, right? Well, not really. Both my neurologist and rheumatologist would prefer that my vitamin D levels measure between 50-80 ng/mL (125-200 nmol/L), a range which conforms nicely to the recommendation of the Vitamin D Council. However, this doesn't mean that YOUR doctors would recommend this for YOU.
How do I get more Vitamin D?
In addition to increasing UVB exposure, you can take over-the-counter vitamin D supplements which provide cholecalciferol (vitamin D3). These tablets are available in doses anywhere from 100 IU to 5000 IU, or even 10,000 IU. Although I had been taking daily doses of 5000 IU vitamin D3 for several months, my serum levels were still too low at the end of this very long, cold winter.
The only prescription form of vitamin D available in the United States is the analogue ergocalciferol (vitamin D2) which is available in 50,000 IU capsules. Ergocalciferol is present in plants and some fish, however this pharmacological substance is synthetic and creates different by-products than does cholecalciferol. All three of my doctors have prescribe ergocalciferol for me at different times. However, many sources I found do not recommend vitamin D2.
Ergocalciferol is said to be less effective in raising serum levels (about only 2/3 as effective as cholecalciferol or vitamin D3), however it had successfully raised my levels to 44 ng/mL last summer before I transitioned to taking 5000 IU vitamin D3 daily. Trying again to get my serum levels above 50 ng/mL, I will continue with 5000 IU of vitamin D3 daily and add once weekly 50,000 IU vitamin D2.
Does obesity affect Vitamin D needs?
Obesity is associated with vitamin D deficiency as vitamin D, a fat soluble substance, is quickly sequestered and stored in the fat cells. Research shared by Dr. Michael F Holick (an expert in vitamin D) states that persons who are obese need 2-3 times the amount of vitamin D than a normal weight individual. This might explain my continued "deficiency" despite significant supplementation.
Please know that the numbers used above are taken from my personal situation and do not represent general recommendations. However, the Vitamin D Council states that daily intake of 5000-10,000 IU vitamin D from all sources is safe in adults, 1000 IU for infants. I will continue to take 5000 IU (D3) daily in addition to 50,000 IU (D2) weekly while getting more sunlight during these summer months; then we'll retest again in August or September.
SELECTED SOURCES FOR FURTHER READING:
Kulie J, Groff A, Redmer J, et al. Vitamin D: An Evidence-Based Review. J Am Board Fam Med 2009; 22:698-706.
Cannell JJ, Hollis BW. Use of Vitamin D in Clinical Practice. Altern Med Rev 2008; 13(1):6-20.
Holick MF. The Vitamin D Epidemic and its Health Consequences. J Nutr 2005; 135: 2739S-2748S.
Grant WB, Holick MF. Benefits and Requirements of Vitamin D for Optimal Health: A Review. Altern Med Rev 2005; 10(2):94-111.
Holick MF. Sunlight and Vitamin D for Bone Health and Prevention of Autoimmune Diseases, Cancers, and Cardiovascular Diseases. Am J Clin Nutr 2004; 80(suppl):1678S-1688S.
Wortsman J, Matsuoka LY, Chen TC, Lu Z, and Holick MF. Decreased bioavailability of vitamin D in obestiy. Am J Clin Nutr 2000; 72:690-693.
April 11, 2010
Weight: 252.6 lbs