Having just passed the winter solstice, we are reminded that many of our patients may not see much of the sun this time of year. The sun that they do see is tangential – and patients in the northern climes in particular are typically covered from head to toe, tending not to linger outdoors "catching rays.
Available data suggest that people living north of the 37th parallel (north of a line from San Francisco to Richmond, Va.) see so little of the sun that it makes the manufacture of vitamin D nearly impossible.
Vitamin D deficiency has been associated with cardiovascular disease, diabetes, osteoporosis, chronic kidney disease, and cancer. But vitamin D deficiency can manifest as nebulous clinical symptoms such as musculoskeletal weakness and pain.
Dr. Ferdinand Schreuder conducted a randomized clinical trial of high-dose vitamin D3 on nonspecific persistent musculoskeletal complaints in vitamin D–deficient non-Western immigrants (Ann. Fam. Med. 2012;10:547-55). The study was conducted in the Netherlands and enrolled non-Western immigrants and their children aged 18-60 years. People were eligible for enrollment if they visited their doctor for frequent, recurrent musculoskeletal pain or pain lasting longer than 3 months without an obvious cause.
Patients were predominantly from the Middle East, Turkey, northern Africa, and Somalia. They were tested for vitamin D, and a serum concentration of 25-hydroxyvitamin D of less than 50 nmol/L was defined as deficiency.
A total of 84 patients were randomized to receive 150,000 IU vitamin D3 orally or matching placebo. At week 6, a second randomization was done for patients who received vitamin D; but all patients who received placebo for the first 6 weeks received a dose of vitamin D for the next 6 weeks. Outcomes were determined at weeks 6 and 12.
Patients in the vitamin D3 group were significantly more likely than those on placebo to report pain relief 6 weeks after treatment (34.9% vs. 19.5%, P = .04). The vitamin D group was also significantly more likely to report improved ability to walk stairs (21.0% vs. 8.4%, P = .008). Serum concentrations of vitamin D were 20 nmol/L at baseline, 63.5 nmol/L at 6 weeks, and 40 nmol/L at 12 weeks.
The vitamin D in this study was given as a single dose, which improves clinical adherence greatly. However, we cannot adroitly translate the findings from this single-dose study to daily dosing of vitamin D.
Some practitioners recommend high daily doses of vitamin D. But we need to be cautious, because vitamin D toxicity can occur. The Institute of Medicine recommends an upper intake level of 4,000 IU/day for individuals older than 9 years, with a reasonable dose about 2,000 IU of vitamin D3.
A reasonable approach may be to test and "treat to target" for vitamin D replacement. Clinical profiling of heavily clothed patients who spend a lot of time indoors from October to March may be wise.
Dr. Ebbert is professor of medicine and primary care clinician at the Mayo Clinic in Rochester, Minn. The opinions expressed are solely those of the author.