Since we are moving into winter, it would be wise for everyone to be mindful of their vitamin D status. We now know that vitamin D affects close to 2,000 genes that have to do with immunity and inflammation. The best vitamin D test to have done is the blood 25 (OH) vitamin D level. A level less than 30 ng/mL is inadequate. Though the Lab Corp normal range is 32 – 100 ng/mL, an optimum level would be 50 – 70 ng/mL. Generally, a prescription is needed for the test, but ZRT Lab and Life Extension offer the test directly without prescription. Out of pocket cost for the test at Lab Corp (with prescription) is $85, and Life Extension and ZRT tests cost a little over $60. With a prescription, insurance may cover some portion of the cost.

The latest data from around the U.S. suggests that more than 90 percent of dark-skinned people (African-Americans, Hispanics and Asians) have vitamin D levels less than 30 ng/mL. What’s more, over 75 percent of the Caucasian population also have levels less than 30 ng/mL. Further, this rate of low vitamin D has doubled in the U.S. in the last ten years.1 The primary reasons seem to be obesity (vitamin D stored in fat is not available), sun-phobia and excess use of sunscreen (this is because we have been told by medical authorities to avoid sun exposure and/or use plenty of sunscreen), and air pollution (which blocks UVB light necessary for the conversion of vitamin D).

There are three things you can do to obtain enough vitamin D:

Correct amount of sun exposure at the right time of day. UVB is available between 10 am and 3 pm (best time is 12 pm to 2 pm). Fair-skinned people may get enough UVB by exposing 25 to 50 percent of their body for 10 to 15 minutes. Darker-skinned people may need one or more hours. If your skin becomes pink (minimal erythema dose, MED) then cut your time by 50 to 75 percent. However, if you live north of Atlanta from November through March, you will not receive enough UVB due to the tilt of the earth away from the sun. Also, if you are over age 70, you have 70 percent less production of vitamin D from sun exposure. Seniors will still benefit from sun exposure but will also need to supplement with vitamin D. In addition, cloud cover can reduce vitamin D synthesis by 50 to 75 percent. On cloudy days, you can get sunburned with UVA rays, and be at risk for cancer and wrinkles, yet not receive the beneficial UVB.2

Sun lamp. High-quality sun lamps replicate natural sunshine. UVA (at 94 to 97.5 percent) and UVB (at 2.5 to 6 percent) exposure times will be basically the same as are found on an ideal day of sun exposure. If you prefer a tanning salon, make sure they use low pressure lamps (look for fluorescent tubes, not round lamps), avoid high pressure lamps which do not provide UVB rays. You may get tan, but you could also get skin damage or cancer.2

Diet and supplements. Generally speaking, everyone should supplement with vitamin D, unless you are impeccable about sun/sun lamp exposure. Infants need 400 to 1,000 iu daily, children 2,000 iu daily and adults 4,000 iu daily as a general starting point. At these doses, you could begin supplementing without a 25 (OH) vitamin D test. After two to three months of supplementation, a blood test will help adjust the dose. If you have questions or concerns, contact a healthcare practitioner who has an understanding of vitamin D. For more information go to, or read the book The Vitamin D Solution by Michael Holick PhD, MD.

1. J.S. Adams and M. Hewison, “Update in vitamin D.” J Clin Endocrinol Metab. 2010 Feb;95(2):471-8.

2. M.F. Holick, The Vitamin D Solution, Hudson Street Press, 2010.