Exogenous Calciferol (Vitamin D) and Vitamin D Endocrine Status among Elderly Nursing Home Residents in the New York City Area

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Abstract
To determine the role and relative importance of sources of exogenous calciferol (vitamin D) in maintaining vitamin D endocrine status in the mid-winter and early spring in a representative sample of institutionalized elderly persons in the New York City area. Cross-sectional survey. A privately-run urban nursing home and the long-term care unit of a suburban public hospital. Residents aged 60 years and older scheduled for a routine annual physical examination and an additional group of individuals ascertained by random sampling. Those with a history of anti-convulsant or glucocorticoid use, liver disease, chronic renal disease (or serum creatinine > 1.5 mg/dL), parathyroid disease, Paget's disease, gastric surgery, or pharmacological vitamin D use were excluded. Of 301 sampled individuals, 221 were found eligible to participate, and 109 were successfully enrolled. The average vitamin D intake was 379 IU/day (range 55-1006 IU/day) and total vitamin D intake was below the Recommended Dietary Allowance in 16% of subjects. Fifty percent of total vitamin D intake came from fortified milk, and 26% came from vitamin supplements. Vitamin supplement use was not associated with low dietary intake. Among subjects taking a supplement containing 400 IU/day, none had serum calcidiol levels below 15 ng/mL, while among subjects with vitamin D intake between 200 and 400 IU/day, 46% had serum calcidiol levels below 15 ng/mL and 14% had calcidiol levels below 10 ng/mL. Vitamin D intake from non-supplement sources (but not from supplements) appeared to have a negative association with serum calcitriol levels. Many nursing home residents may require vitamin supplements in order to achieve optimal levels of calciferol replacement. The choice of a vehicle for calciferol replacement may affect calcitriol levels.