BOSTON, MASSACHUSETTS. Vitamin D deficiency has been clearly linked to an increase in bone loss and a higher risk for bone fractures and osteoporosis. Vitamin D is an essential precursor for 25-hydroxyvitamin D (formed in the liver) which again is a precursor for the active hormone 1,25-dihydroxyvitamin D which is synthesized in the kidneys. There have been widespread reports of the prevalence of vitamin D deficiency among older people. Now researchers at Harvard Medical School weigh in with a new report which provides clear evidence that the problem may be much worse than originally thought. The study involved 290 patients admitted to a general medical ward in March and September 1994. A total of 57 per cent of the study participants were found to be vitamin D deficient as indicated by a serum concentration of less than 15 ng/ml of 25- hydroxyvitamin D. Twenty-two per cent of the patients were severely deficient as indicated by a serum concentration of less than 8 ng/ml. The average (mean) daily intake of vitamin D was found to be only 300 IU (7.5 micrograms) and 67 per cent of the patients reported intakes less than the current recommended daily amount (200 IU for adults 19 to 50 years old, 400 IU for adults 51 to 70 years old, and 600 IU for adults 71 years or older). The researchers found that serum 25-hydroxyvitamin D concentrations were inversely proportional to parathyroid hormone concentrations. They also noted that a low vitamin D intake, inadequate sunlight exposure, the winter season, and being housebound all increased the risk of being vitamin D deficient. Anticonvulsant-drug therapy, renal dialysis, and hypertension were also found to be important risk factors for vitamin D deficiency. Among patients less than 65 years old and with no known risk factors for vitamin D deficiency 42 per cent were found to be vitamin D deficient. Deficiencies were common even among patients with vitamin D intakes in excess of the recommended daily amount. The researchers conclude that routine vitamin D supplementation or widespread screening should be considered.
In an accompanying editorial Dr. Robert Utiger, MD emphasizes the recommendation
that sick adults, older adults, and perhaps all adults probably need 800-1000
IU/day. He points out that vitamin D can be given as single weekly doses of
5000 IU or as doses of 100,000 IU every four or six months. Vitamin D is
entirely safe in doses not exceeding 2400 IU/day. Dr. Utiger concludes his
review with the statement "The amount of vitamin D in supplemental multivitamins
or calcium supplements should be increased substantially, and all adults should
be advised to take them."