Hypovitaminosis D in Medical Inpatients
June 1, 1998 3 minutes read
Hypovitaminosis D in Medical Inpatients
ABSTRACT & COMMENTARY
Vitamin d deficiency is a risk factor for osteopenia, osteomalacia, and bone fractures. Vitamin D supplementation has been shown to reduce bone fractures in the elderly, but it is not clear how common vitamin D deficiency is in younger individuals. The present study analyzed serum 25-hydroxyvitamin D concentrations in 290 patients consecutively admitted to a general medical service in March and September of 1994 at the Massachusetts General Hospital in Boston. March and September were chosen because the seasonal variation in sunlight predicted that levels would be maximal in September and minimal in March. Patients with medical conditions predisposing to vitamin D deficiency were excluded. The cutoff normal for 25-hydroxyvitamin D was set at 15 ng/mL, because a previous study found that levels below this correlate with low bone mass in postmenopausal women (Villareal DT, et al. J Clin Endocrinol Metab 1991;72:628-634). Fifty-seven percent of the 290 inpatients had deficient vitamin D levels. Twenty-two percent were severely deficient, with levels below 8 ng/mL. Sixty-three percent of those studied in March and 49% studied in September were vitamin D deficient. Forty-two percent of those with no risk factors for vitamin D deficiency who were younger than 65 years old were deficient. Likewise, 46% of those taking multivitamins were vitamin D deficient. Since the half-life is three weeks, low levels were unlikely to be due to recent illness. The use of historical criteria only identified 59% of those who were deficient, and, thus, the only way to know if someone has enough vitamin D is to measure it. Thomas and colleagues note that hypovitaminosis D not only causes faulty or absent bone accretion, but it is also associated with muscle weakness and pain, progression of osteoarthritis, and impaired macrophase activation. (Thomas MK, et al. N Engl J Med 1998;338:777-783.)
COMMENT BY SARAH L. BERGA, MD
This study identified an alarming public health problem, namely, vitamin D deficiency. In the accompanying editorial, Utiger (N Engl J Med 1998;338:828-829) notes that the newly revised recommendations issued by the Food and Nutrition Board of the Institute of Medicine may still be too slow. Adequate intake was recommended to be 200 IU for those patients 19-50 years, 400 IU for those patients 51-70 years, and 600 IU for those patients older than 71 years. Assuming that higher levels are needed, what should be the source?
The wavelength of sunlight needed to convert 7-dehydrocholesterol to previtamin D is in the ultraviolet range and causes sunburn and skin cancer. Sunblock blocks these wavelengths, but it also prevents the skin from manufacturing previtamin D. Therefore, more sunlight is not the answer. As the study showed, multivitamin use did not correlate with serum vitamin D levels, possibly because of poor absorption. Few foods are fortified with vitamin D, apparently because of concerns about toxicity. However, as this study highlights, deficiency, not toxicity, is the real concern-therefore, increased fortification was advocated in the editorial. Milk is one food commonly fortified and some cereals are also fortified. Each 8 oz glass of milk, even the fat-free type, has 100 IU. Other dairy foods, such as cheese and ice cream, are generally not fortified. The one strategy to avoid is taking two multivitamins daily; this will lead to toxic levels of vitamin A and possibly other vitamins. Regardless of the dietary or supplemental strategy used, this study suggests that the only way to see if levels are in the right range is to measure 25-hydroxyvitamin D in the circulation. Previtamin D is converted to 25-hydroxyvitamin D in the liver, and the active compound 1,25-dihydroxyvitamin D is made by the kidneys. Don't measure 1,25-dihydroxyvitamin D, however, because it has a short half-life and it will not provide an accurate assessment. Adult well-care may be unfashionable and poorly reimbursed, but, at the very least, patients should receive a one-minute sound byte when seen in the office. Patients with documented osteoporosis should have their vitamin D level checked.
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