Studies show that over 30% of Americans may not have sufficient levels of Vitamin D.
The United States may be suffering from an epidemic of Vitamin D deficiency, whose symptoms range from subtle bone pain and muscle weakness to serious cardiovascular issues, cognitive impairment, and cancer; low Vitamin D can increase the risk of diabetes, hypertension, and multiple sclerosis.
Luckily, 5-10 minutes of unprotected sun exposure a few times a week should be enough for our bodies to manufacture sufficient Vitamin D. So, as archaeologists who spend thousands of hours in the sun over our lifetimes, we have nothing to worry about, right?
Not necessarily. We can’t assume that just because we work outside that our bodies are manufacturing and absorbing Vitamin D effectively.
The first time I had my Vitamin D tested was in August 2010, after I had spent about 360 hours in the sun doing fieldwork for the summer. Two-thirds of those hours had been in Havana, Illinois, situated at 40.3° N, which has a UV index of about 8.5 in June, which is a “Very High” level of UV radiation.
When the doctor suggested I might be low in Vitamin D, I thought that was a ludicrous suggestion, but I thought the test couldn’t hurt. It turned out that after all that sunshine, my Vitamin D level was barely adequate according to the most forgiving scale. My Serum 25-Hydroxyvitamin D [25(OH)D] level was 21 ng/mL. That level is well within the “deficient” range according to most testing laboratories and the Vitamin D Council and barely better than “deficient” according to the Endocrine Society. I was baffled; how could this be?
|<30||<12||Associated with vitamin D deficiency, leading to rickets in infants and children and osteomalacia in adults|
|30–50||12–20||Generally considered inadequate for bone and overall health in healthy individuals|
|≥50||≥20||Generally considered adequate for bone and overall health in healthy individuals|
|>125||>50||Emerging evidence links potential adverse effects to such high levels, particularly >150 nmol/L (>60 ng/mL)|
* Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).
** 1 nmol/L = 0.4 ng/mL
|Vitamin D Council||Endocrine Society||Food and Nutrition Board||Testing Laboratories|
|Deficient||0-30 ng/ml||0-20 ng/ml||0-11 ng/ml||0-31 ng/ml|
|Insufficient||31-39 ng/ml||21-29 ng/ml||12-20 ng/ml|
|Sufficient||40-80 ng/ml||30-100 ng/ml||>20 ng/ml||32-100 ng/ml|
Being a scientist, I decided to conduct an empirical test to determine the effects of my work in the sun on my Vitamin D levels. In 2011, I had my Vitamin D tested in May, after nine months of graduate school studies in the library. My Vitamin D level was on the verge of dangerously low: a mere 15 ng/mL. I then proceeded to spend about 440 hours doing fieldwork in the sun in Mackinaw City, situated at 45.8° N, which has a UV index averaging around a 7, which is still in the “High” range, for the months of June, July, and August. After all that sunshine, my Vitamin D was still only 24 ng/mL.
So, it turned out that my fieldwork in the sun did have an impact on my Vitamin D levels, and a significant impact at that! But it still wasn’t enough to raise my Vitamin D levels to a healthy range.
Since then, I try to take a 1000 IU Vitamin D supplement daily. Vitamin D can be difficult to get from food, but fish is one of the best sources, especially salmon, mackerel, and tuna! Other foods rich in Vitamin D include fortified cereals, oysters, eggs, salami, and mushrooms.
But remember, always consult your own health care professional for your individual health questions and concerns!