Lab Efficiency Series
In 2011, all health professionals must recognize the necessity of vitamin D testing and the importance of treating deficiency. Vitamin D deficiency is a worldwide phenomenon, even in sunny countries such as Australia, Italy, Egypt and Mexico. In the last two years alone, more than 16,000 new research papers on vitamin D have been archived in the National Library of Medicine's PubMed. Many of these peer-reviewed articles document compelling associations between vitamin D status and medical conditions that affect millions of Americans. Paralleling this surge in research has been a concomitant surge in vitamin D testing.
The more we test, the more unexpected deficiencies we find. Examples of such unexpected findings here in Minnesota range from adults of all ages to pregnant women on prenatal vitamins to healthcare professionals.
Despite extensive publicity on vitamin D deficiency in medical journals and the lay press, in 2010, within the Allina Health Care system in Minnesota, more than 30% of 10,700 employees were found to have levels less than 20 ng/ml and 6% had levels less than 10 ng/ml. Medical professionals may not recognize either their own risk, or their patients' risk, for vitamin D deficiency.
Patient advocacy and self-care both mean ensuring normal vitamin D levels via measurement. For those who are already deficient in vitamin D, taking a multivitamin and some milk every day is not enough for replenishment. Because of normal human variation in BMI, skin color, age, latitude, medication use, absorption and metabolism, effective replenishment requires measurement by the clinical laboratory and careful monitoring by healthcare professionals.
To give some insight into counseling that physicians may provide a patient, I share with you the following account based on a real case study.
A previously healthy 42-year-old African-American woman consulted with her primary care physician because of two years of worsening fatigue, generalized aches and subjective weakness. She was surprised by the persistence of these symptoms as she exercises frequently, eats well and takes a multivitamin each day. She noted some decreased mood but did not test outside of normal for common mood associated tests such as thyroid, blood sugars or more serious illnesses.
The range of possibilities to explain these symptoms is quite broad. Both her physical exam and an extended review of symptoms were normal, which means that her diagnosis will be made based upon laboratory studies. Of the many lab tests that could be ordered, vitamin D is one that should be ordered, as low vitamin D is associated clinically with fatigue, myalgias, weakness and many other non-specific symptoms.
Results and the Patient-Physician Dialogue
The patients' complete blood count, electrolytes, BUN/creatinine, glucose and TSH all returned within normal limits. However, her total 25-OH-vitamin D level returned at 12 ng/ml (normal range 30-70 ng/ml). This finding allowed her physician to make the diagnosis of vitamin D deficiency and begin replenishment therapy. Because of her generally healthy lifestyle, the patient was shocked by her diagnosis.
Her doctor explained that risk factors for low vitamin D include dark skin, larger body sizes (BMI), wearing sun screen, working long hours indoors and living north of Atlanta, GA. For many people, taking a multivitamin is not enough to maintain a normal vitamin D level.
Her doctor noted that our skin, when exposed to the right amount of ultraviolet B (UVB) light from the sun, will make the same vitamin D that is found in most multivitamins and vitamin D supplements. SPF sun blocks will block the body's capacity to make vitamin D.
Many people work indoors and are unable to spend significant time in the sun. Why isn't a multivitamin enough to compensate for the lack of sunshine?
Multivitamins most often contain 400 IUs of vitamin D. Some prenatal vitamins contain only 200 IUs. For comparison, a summer afternoon at the beach could be as much as 20,000 IUs, which is about the amount of vitamin D found in 50 multivitamins, 100 prenatal vitamins or 12 gallons of milk.
It's also important to remember that a multivitamin is a "one-size fits all" approach to public health. That is fine for B vitamins, but, especially with vitamin D, there is a difference between African-American and Caucasian, young and old, thin and big, Tampa, FL, and Anchorage, AK. Some people do well on just a multivitamin and some people require prescription doses of vitamin D. The difference can only be determined by blood tests. Like with cholesterol levels, physical exams can't predict levels.
National guidelines on replacement do not exist. Toxicity from supplementation is extremely rare and requires massive doses acutely or very large doses (greater than 10,000 IUs per day) for long periods of time. Replenishment requires extra care in primary hyperparathyroidism (which can co-exist with vitamin D deficiency) and secondary hyperparathyroidism (to ensure absence of primary hyperparathyroidism).
Clinically, what really counts is not the vitamin D dose but the serum level achieved. For replenishment, follow up testing may be required every three months to ascertain effectiveness of dosing. Replenishment dosing will not equal maintenance dosing. Once the clinician has switched to maintenance dosing, the testing frequency can be reduced significantly.
The definition of the normal reference range for 25-OH-vitamin D is controversial. The Institute of Medicine of the National Academy of Sciences recently lowered the internationally accepted definition of vitamin D sufficiency from 30 ng/ml to 20 ng/ml. This was based on extrapolations of the best value for clinical outcomes related to bone health. In contrast, the Endocrine Society recently recommended a serum level of 40-60 ng/ml for optimal clinical outcomes for overall health. These contradictory statements mean that more prospective randomized trials are needed.
Dr. Plotnikoff is senior consultant, Allina Center for Health Care Innovation.