The 3 epimer of 25-hydroxycholecalciferol is present in the circulation of the majority of adults in a nationally representative sample and has endogenous origins.
Fundamental knowledge gaps in relation to the 3 epimer of 25-hydroxycholecalciferol [3-epi-25(OH)D₃] limit our understanding of its relevance for vitamin D nutrition and health. The aims of this study were to characterize the 3-epi-25(OH)D₃ concentrations in a nationally representative sample of adults and explore its determinants. We also used data from a recent randomized controlled trial (RCT) of supplemental cholecalciferol (vitamin D₃) conducted in winter in older adults to directly test the impact of changes in vitamin D status on serum 3-epi-25(OH)D3 concentrations. Serum 25-hydroxycholecalciferol [25(OH)D₃] and 3-epi-25(OH)D₃ concentrations (via LC-tandem mass spectrometry) from our vitamin D₃ RCT in adults (aged ≥50 y) and data on dietary, lifestyle, and biochemical characteristics of participants of the recent National Adult Nutrition Survey in Ireland (aged 18-84 y; n = 1122) were used in the present work. In the subsample of participants who had serum 3-epi-25(OH)D₃ concentrations greater than the limit of quantification (n = 1082; 96.4%), the mean, 10th, 50th (median), and 90th percentile concentrations were 2.50, 1.05, 2.18, and 4.30 nmol/L, respectively, whereas the maximum 3-epi-25(OH)D₃ concentration was 15.0 nmol/L. A regression model [explaining 29.9% of the variability in serum 3-epi-25(OH)D₃] showed that age >50 y, vitamin D supplement use, dietary vitamin D, meat intake, season of blood sampling, and sun exposure habits were significant positive determinants, whereas increasing waist circumference and serum 25-hydroxyergocalciferol concentration were significant negative determinants. The RCT data showed that mean serum 25(OH)D₃ and 3-epi-25(OH)D₃ concentrations increased (49.3% and 42.1%, respectively) and decreased (-28.0% and -29.1%, respectively) significantly (P < 0.0001) with vitamin D₃ (20 μg/d) and placebo supplementation, respectively, over 15 wk of winter. In conclusion, we provide data on serum 3-epi-25(OH)D₃ in a nationally representative sample of adults. Our combined observational and RCT data might suggest that both dietary supply and dermal synthesis of vitamin D₃ contribute to serum 3-epi-25(OH)D₃ concentration.
School of Food and Nutritional Sciences and Department of Medicine, University College Cork, Cork, Ireland k.cashman@ucc.ie.
Kevin D
KD
Cashman
School of Food and Nutritional Sciences and.
Michael
M
Kinsella
School of Food and Nutritional Sciences and.
Janette
J
Walton
School of Food and Nutritional Sciences and.
Albert
A
Flynn
School of Food and Nutritional Sciences and.
Aoife
A
Hayes
School of Food and Nutritional Sciences and.
Alice J
AJ
Lucey
School of Food and Nutritional Sciences and.
Kelly M
KM
Seamans
School of Food and Nutritional Sciences and.
Mairead
M
Kiely
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015652:25-Hydroxyvitamin D 2 / Q000031:analogs & derivatives / Q000097:blood / Q000737:chemistry / Q000378:metabolism; D002112:Calcifediol / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism; D002762:Cholecalciferol / Q000378:metabolism / Q000627:therapeutic use; D019587:Dietary Supplements; D004311:Double-Blind Method; D007494:Ireland / Q000453:epidemiology; D008460:Meat; D009749:Nutrition Surveys; D015995:Prevalence; D012621:Seasons; D012720:Severity of Illness Index; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D013237:Stereoisomerism; D013472:Sunlight; D014808:Vitamin D Deficiency / Q000178:diet therapy / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology; D016032:Randomized Controlled Trials as Topic
D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol; D002762:Cholecalciferol