A research team based at the Massachusetts General Hospital (MGH) has found that a surprising number of adult hospital inpatients were deficient in vitamin D, a nutrient required for the maintenance of healthy bones. In their study of 290 patients admitted to the hospital's medical service, they found that 57 percent could be considered deficient in vitamin D and 22 percent severely deficient. The patients represented a wide range of ages and medical diagnoses; and even in a subgroup of 77 patients with no known risk factors for vitamin D deficiency, 41 percent showed levels that could be considered deficient. The report appears in the March 19 issue of the New England Journal of Medicine.
"Although we expected to see significant levels of vitamin D deficiency in the patients studied, we were that surprised the results were so dramatic," says Joel Finkelstein, MD, of the MGH endocrine unit, the paper's senior author. "This finding suggests that vitamin D deficiency is more common than currently appreciated in the general population as well."
Vitamin D helps the body absorb minerals such as calcium and phosphorus, which are critical components of bone. The body manufactures the vitamin in response to sunlight, and its primary dietary source is through fortified dairy products. Vitamin D deficiency in adults can cause a softening of the bones called osteomalacia and is associated with an increased risk of fractures in the elderly.
The team studied two groups of patients: 150 who were consecutively admitted to the MGH medical service in March 1994 and 140 consecutively admitted in September 1994. Previous studies had found that vitamin D levels were lowest and highest during these months among people in the Boston area. The researchers reviewed patients' records for a variety of characteristics that might affect vitamin D levels, interviewed participants about their diets and sun exposure, and tested blood samples for levels of vitamin D and parathyroid hormone, which plays a major role in the exchange of calcium between the bones and the bloodstream.
The results showed that 164 participants (57 percent) had vitamin D levels that current research suggests could be considered deficient: 99 had vitamin D levels between 8 and 15 nanograms per milliliter (ng/ml), indicating moderate deficiency; and 65 had levels less than 8 ng/ml, indicating severe deficiency. In a subgroup of 77 patients with none of the known risk factors for vitamin D deficiency -- factors like being age 65 or over, being housebound or in a nursing home, having certain chronic illnesses or taking certain drugs -- 32 patients (41 percent) were deficient in vitamin D. Patients with lower vitamin D levels also showed higher levels of parathyoid hormone, which the body may produce in an effort to compensate for vitamin D deficiency.
"Our study suggests that the standard clinical indicators may not adequately predict who is at risk for vitamin D deficiency," says Melissa Thomas, MD, PhD, the study's first author. "Although we don't currently know which of the patients with vitamin D deficiency will someday have problems like fractures and osteoporosis, we believe that more patients should be screened and treated for low vitamin D levels."
The researchers note that many of the study participants who reported vitamin D intakes in line with current recommendations -- based on both consumption of dairy foods and taking vitamin supplements -- still showed deficient blood levels of vitamin D. Among those with intakes above the age-adjusted recommended levels, 37 percent were found to be vitamin D deficient.
"In addition to its known effects on bone metabolism, vitamin D is implicated in a variety of other important areas -- including muscle function, progression of arthritis and aspects of the immune system," says Finkelstein. "Because vitamin D deficiency appears to be so common, more people probably should consider taking vitamin D supplements."
Additional coauthors of the study are Donald Lloyd-Jones, MD, Ravi Thadhani, MD, MPH, Albert Shaw, MD, PhD, Donald Deraska, MD, Barrett Kitch, MD, and Eleftherios Vamvakas, MD, PhD, all of the MGH; Ian Dick, MSc, of the University of Western Australia, and Richard Prince MD, of Sir Charles Gairdner Hospital, Perth, Australia. The research was supported by grants from the National Institutes of Health.
Journal
New England Journal of Medicine