[25-Hydroxyvitamin D levels in infants. Relation with breast-feeding]

To determine the prevalence of subclinical vitamin D deficiency among infants in Valencia, Spain (latitude 39.5 degrees N) and its relation with breast- feeding.

Serum levels of calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D (25-OHD) and intact parathyroid hormone (PTH) were measured in 60 term infants aged between 1 and 6 months (mean age: 3.9 months), with no known bone, gastrointestinal or renal disease (33 exclusively breast-fed, 27 bottle-fed). Data on vitamin D supplementation and weekly direct sunlight exposure were also gathered.

All infants had normal serum calcium, phosphate and PTH levels. Five infants (8.3 %) had 25-OHD levels < 10 ng/ml (lower limit of normality) and all of these infants were breast-fed (15.1 % of the group). None of these five infants received vitamin D supplementation. Infants with vitamin D deficiency had slightly elevated serum alkaline phosphatase. Only 48 % of breast-fed infants received regular vitamin D supplementation. The mean serum 25-OHD concentration of breast-fed infants in winter (16.8 ng/ml) was significantly lower than that in bottle-fed infants in summer (23.6 ng/ml, p < 0.05).

In breast-fed infants, the association of limited sunshine exposure and poor dietary vitamin D supplementation confers a high risk of subclinical vitamin D deficiency, even in regions with a temperate climate.