Estimation of the dietary requirement for vitamin D in healthy adults.

The American journal of clinical nutrition
Q1
Dec 2008
Citations:263
Influential Citations:6
Interventional (Human) Studies
87
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Methods
Two-center, double-blind, randomized, placebo-controlled trial in apparently healthy white men and women aged 20–40 years; 245 recruited, 238 started, 221 completed; locations: Cork (Ireland) and Coleraine (Northern Ireland).
Intervention
Vitamin D3 capsules; 0, 5, 10, and 15 g/d for 22 weeks; taken orally as capsules.
Results
Vitamin D3 supplementation produced dose-related increases in serum 25(OH)D during winter. The slope of intake versus serum 25(OH)D was 1.96 nmol/L per g/d. To maintain 25 nmol/L in 97.5% of 20–40-year-olds, a daily intake of 8.7 g/d is needed, varying with sun exposure: 7.2 g/d (sunny), 8.8 g/d (some sun), 12.3 g/d (sun-avoiding). For 37.5, 50, and 80 nmol/L, the intakes were 19.9, 28.0, and 41.1 g/d, respectively. Across sun-exposure groups, the required intakes span 7.2–41.1 g/d to maintain winter vitamin D status above selected cutoffs. Authors conclude that summer skin synthesis does not suffice to maintain adequate winter vitamin D in most people; dietary vitamin D remains essential, and findings support reconsideration of dietary vitamin D recommendations.
Limitations
Only 17% achieved winter 25(OH)D ≥80 nmol/L, likely due to the maximum 15 g/d dose; higher-dose winter trials (20–40 g/d) are needed to confirm high-end targets; study limited to white adults aged 20–40 y at latitudes 51–55°N; sun exposure and dietary intake were self-reported, potentially introducing misclassification and bias; generalizability to other populations is limited.

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...