Estimation of the dietary requirement for vitamin D in free-living adults greater-than-or-equal64 y of age

• Published in: The American journal of clinical nutrition Vol. 89; no. 5; pp. 1366 - 1374
• Main Authors: Cashman, Kevin D, Wallace, Julie MW, Horigan, Geraldine, Hill, Tom R, Barnes, Maria S, Lucey, Alice J, Bonham, Maxine P, Taylor, Nicola, Duffy, Emeir M, Seamans, Kelly, Muldowney, Siobhan, FitzGerald, Anthony P, Flynn, Albert, Strain, JJ, Kiely, Mairead
• Format: Journal Article
• Language: English
• Published: American Society for Clinical Nutrition 2009
• Subjects: 25-hydroxycholecalciferol; adults; clinical trials; deficiency diseases; dietary nutrient sources; dietary recommendations; estimation; human nutrition; nutrient deficiencies; nutrition assessment; nutritional status; seasons; solar radiation; vitamin D
• ISSN: 0002-9165; 1938-3207

BACKGROUND: Older adults may be more prone to developing vitamin D deficiency than younger adults. Dietary requirements for vitamin D in older adults are based on limited evidence. OBJECTIVE: The objective was to establish the dietary intake of vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above various cutoffs between 25 and 80 nmol/L during wintertime, which accounted for the effect of summer sunshine exposure and diet. DESIGN: A randomized, placebo-controlled, double-blind, 22-wk intervention was conducted in men and women aged greater-than-or-equal64 y (n = 225) at supplemental levels of 0, 5, 10, and 15 μg vitamin D₃/d from October 2007 to March 2008. RESULTS: Clear dose-related increments (P < 0.0001) in serum 25(OH)D were observed with increasing supplemental vitamin D₃ intakes. The slope of the relation between total vitamin D intake and serum 25(OH)D was 1.97 nmol · L⁻¹ · μg intake⁻¹. The vitamin D intake that maintained serum 25(OH)D concentrations >25 nmol/L in 97.5% of the sample was 8.6 μg/d. Intakes were 7.9 and 11.4 μg/d in those who reported a minimum of 15 min daily summer sunshine exposure or less, respectively. The intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 17.2, 24.7, and 38.7 μg/d, respectively. CONCLUSION: To ensure that the vitamin D requirement is met by the vast majority (>97.5%) of adults aged greater-than-or-equal64 y during winter, between 7.9 and 42.8 μg vitamin D/d is required, depending on summer sun exposure and the threshold of adequacy of 25(OH)D. This trial was registered at http://www.controlled-trials.com/ISRCTN20236112 as ISRCTN registration no. ISRCTN20236112.