Estimation of the dietary requirement for vitamin D in healthy adults.
What this study found
Higher oral vitamin D3 doses were associated with higher end-of-winter 25(OH)D concentrations, but concentrations still declined from baseline in all three dose groups. Median 25(OH)D fell from 60.0 to 49.7 nmol/L with 5 g/day, from 72.2 to 60.0 nmol/L with 10 g/day, and from 75.9 to 69.0 nmol/L with 15 g/day. PTH increased from 46.9 to 52.0 ng/mL, 43.1 to 50.5 ng/mL, and 38.4 to 43.0 ng/mL, respectively. No adverse events were reported. Overall, the findings support a dose-response relationship and indicate that winter vitamin D needs vary with baseline status and prior sun exposure.
- Study & population
- Interventional human study in apparently healthy white men and women aged 20-40 years recruited from Cork, Ireland, and Coleraine, Northern Ireland.
- Intervention
- Oral vitamin D3 capsules were given daily for 22 weeks in three dose arms: 5 g/day, 10 g/day, or 15 g/day.
- Key limitation
- No placebo or control arm is described in the extracted active-arm data, so interpretation is based on dose-response and pre-post changes rather than a direct untreated comparison.
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Open PDFOriginal abstract
BACKGROUND Knowledge gaps have contributed to considerable variation among international dietary recommendations for vitamin D. OBJECTIVE We aimed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above several proposed cutoffs (ie, 25, 37.5, 50, and 80 nmol/L) during wintertime after adjustment for the effect of summer sunshine exposure and diet. DESIGN A randomized, placebo-controlled, double-blind 22-wk intervention study was conducted in men and women aged 20-40 y (n = 238) by using different supplemental doses (0, 5, 10, and 15 microg/d) of vitamin D(3) throughout the winter. Serum 25(OH)D concentrations were measured by using enzyme-linked immunoassay at baseline (October 2006) and endpoint (March 2007). RESULTS There were clear dose-related increments (P < 0.0001) in serum 25(OH)D with increasing supplemental vitamin D(3). The slope of the relation between vitamin D intake and serum 25(OH)D was 1.96 nmol x L(-1) x microg(-1) intake. The vitamin D intake that maintained serum 25(OH)D concentrations of >25 nmol/L in 97.5% of the sample was 8.7 microg/d. This intake ranged from 7.2 microg/d in those who enjoyed sunshine exposure, 8.8 microg/d in those who sometimes had sun exposure, and 12.3 microg/d in those who avoided sunshine. Vitamin D intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 19.9, 28.0, and 41.1 microg/d, respectively. CONCLUSION The range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status [as defined by incremental cutoffs of serum 25(OH)D] in the vast majority (>97.5%) of 20-40-y-old adults, considering a variety of sun exposure preferences, is between 7.2 and 41.1 microg/d.