Vitamin D deficiency was common among children in the
United Kingdom, and although there were common risk factors for lower
25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 levels,
there were also distinct risk factors for each, according to researchers from
the University of Bristol, England.
Data were taken from the Avon Longitudinal Study of
Parents and Children, a population-based birth cohort from southwest England.
Of the 14,062 live births included in the cohort — established between
April 1991 and December 1992 — 7,560 of the children had data on serum
25-(OH)D3 and 25-(OH)D2 concentrations. These nonfasting
blood samples were collected at a mean age of 9.9 years.
The median levels were 22.3 mg/mL for
25-(OH)D3, 1.4 ng/mL for 25-(OH)D2 and 24.3 ng/mL for
total 25-(OH)D. In all, 2,158 children were
vitamin D deficient, with total 25-(OH)D levels of less than
20 ng/mL, and 5,631 children were vitamin D insufficient, with 25-(OH)D levels
of less than 30 ng/mL.
Vitamin D deficiency was more common during the winter
months. Winter season, higher age, female gender, nonwhite ethnicity, lower
household income, rental housing, time spent outdoors during summer and higher
Tanner stage were associated with vitamin D deficiency.
Lower 25-(OH)D3 and D2 levels were
associated with age, gender, puberty stage, BMI, physical activity, household
income and maternal education. Ethnicity, vitamin D intake, time spent outdoors
and UVB protection score were associated with 25-(OH)D3 only.
Protein and carbohydrate intake, parents’ social class and housing tenure
were associated with 25-(OH)D2 only.
“Sources for these two forms are different, and our
study showed that despite some overlap, there are differences in potential
confounding structures for association studies of 25-hydroxyvitamin
D3 and 25-hydroxyvitamin D2,” the researchers wrote.
“Future studies should consider these differences when assessing
associations of vitamin D status with health outcomes.”
Mark A. Sperling
This study doesn’t say that much new that we don’t know. There
are two ways we can get vitamin D: Sunshine is the main source of vitamin
D3, and green leafy vegetables are the main source of vitamin
D2. Nonwhite children had less D3, which is
understandable because they have a natural sun block. Children who spent time
outdoors had higher D3 levels, which is also understandable. Boys
had increased D3 levels and D2 levels, which is
understandable because boys spend more time outdoors. Also of interest, obese
children had lower D3 levels and D2 levels because they
don’t often spend time outdoors nor do they eat the healthy vegetables.
– Mark A. Sperling, MD
Editorial Board member
Disclosure: Dr. Sperling reports no relevant