Vitamin D status of schoolchildren in Northern Algeria, seasonal variations and determinants of vitamin D deficiency

Summary There are no published data on the vitamin D status
of children living in North Africa. In 435 healthy Algerian
children 5–15 years old, we found that vitamin D insufficiency
(serum 25-hydroxyvitamin D (25OHD) <50 nmol/L) was
frequent, especially in winter. Low vitamin D status was
associated with increased parathyroid hormone (PTH) and
leg deformation
Introduction As there are no published data on the vitamin D
status of children living in North Africa, we evaluated the
25OHD concentration of healthy Algerian children at the end
of summer and at the end of winter. As secondary objectives,
we studied the various determinants of vitamin D status and
the PTH-25OHD relationship in these subjects.
Methods Four hundred thirty-five children 5–15 years old
were examined and had a blood sample in September 2010.
Of them, 408 were sampled again in March 2011.
Results Median 25OHD concentration in the whole group
was 71.4 nmol/L in September and 52.9 nmol/L in March.
In September, 58.4, 29.9, and 8.1 % had a 25OHD concentration
below 75, 50, and 30 nmol/L respectively. In March,
these percentages increased to 65.2, 41.4, and 17.4 % for the
75, 50, and 30 nmol/L threshold, respectively. In multivariate
analysis, older age, darker skin phototype, low daily vitamin
D and calcium intake, poor socioeconomic status, and short
daily sun exposure remained significantly associated with a
25OHD <50 nmol/L at both visits. In 72 (16.6 %) children,
genu varum/valgum was present. Compared to the 363 children
without leg deformation, they presented more frequently
with the risk factors of vitamin D insufficiency. They also had
lower 25OHD concentrations and higher PTH and tALP.
Serum PTH and 25OHD concentrations were negatively and
significantly correlated (r=−0.43; p<0.001) without a
25OHD threshold above which PTH does not decrease
anymore.
Conclusion Despite a sunny environment, vitamin D insufficiency
is frequent in healthy Algerian children.