Does vitamin D status track through adolescence?
BACKGROUND
To our knowledge, no studies have reported on the long-term variability of vitamin D status in adolescents.


OBJECTIVE
To determine whether tracking of vitamin D status occurs in healthy adolescents, we assessed the variability of 25-hydroxyvitamin D [25(OH)D] every 2 y over a 10-y period in a longitudinal cohort of adolescents living in Johannesburg, South Africa (latitude 26°S).


METHODS
Healthy adolescents who had blood samples available on ≥3 occasions between 11 and 20 y of age were included in the study. Of the cohort of 504 children, 99 met the criteria. The mean 25(OH)D concentration at each time point was measured, and the individual 25(OH)D z scores based on year 11 values were used as the reference. All 25(OH)D concentrations for a subject were measured in a single assay.


RESULTS
No significant correlation was found between 25(OH)D in the earlier and later years of adolescence, although significant correlations were found between year 11 and year 13 (r = 0.71, P < 0.0001) and between years 15, 17, and 20 (r ≥ 0.65, P < 0.0001). The percentage of adolescents whose 25(OH)D concentration changed by >20 nmol/L from year 11 was calculated for all age groups: 12% of the cohort had a change of >20 nmol/L at 13 y of age compared with 46% at 20 y of age. Just more than one-half (53%) of the cohort changed their category of vitamin D status between the ages of 11 and 20 y, and one-third of adolescents changed from being replete to insufficient over the same period.


CONCLUSIONS
The data suggest that the measurement of 25(OH)D at a single time point does not reflect the long-term vitamin D status of an adolescent. These findings may cast doubt on the veracity of those studies that suggest an association of vitamin D status with various disease states in which vitamin D status was measured only once.
MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics and Division of Orthopaedic Surgery, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa machuene.poopedi@wits.ac.za.
Machuene A
MA
Poopedi
MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics and.
Shane A
SA
Norris
MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics and.
Lisa K
LK
Micklesfield
MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics and.
John M
JM
Pettifor
D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D000293:Adolescent; D041923:Adolescent Development; D017195:Adolescent Nutritional Physiological Phenomena; D000328:Adult; D002112:Calcifediol / Q000097:blood; D002648:Child; D002657:Child Development; D002664:Child Nutritional Physiological Phenomena; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D009752:Nutritional Status; D011446:Prospective Studies; D012720:Severity of Illness Index; D013019:South Africa / Q000453:epidemiology; D014504:Urban Health; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology* / Q000503:physiopathology; D055815:Young Adult
D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol
25-hydroxyvitamin D; South Africa; adolescence; tracking; vitamin D status; z scores