Biochemical markers of bone metabolism in children with cow's milk allergy

INTRODUCTION Patients with cow's milk allergy (CMA) and following a cow milk protein-free diet for a long time are potentially at risk of developing bone abnormalities. To assess the balance between bone formation and resorption processes, we determined serum concentrations of osteocalcin (OC), bone alkaline phosphatase (BALP), C-terminal telopeptide of type I collagen (CTX), fetuin-A, osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) in children with CMA. MATERIAL AND METHODS The study included 50 prepubertal children with diagnosed cow's milk allergy, who were under systematic medical and nutritional care at the Institute of Mother and Child and 40 healthy counterparts as a control group. The concentrations of bone metabolism markers were determined by immunoenzymatic assays. RESULTS The diets of all investigated children were correct in terms of phosphorus and magnesium contents but deficient in terms of calcium and vitamin D. Serum OC and CTX as well as fetuin-A concentrations were similar in both studied groups. The BALP activity was significantly (p < 0.05) higher in children with cow's milk allergy than in the controls. Serum OPG concentration was comparable in both groups, but the RANKL level was higher (p < 0.05) in CMA children than in healthy ones. Hence, the ratio of OPG/RANKL was lower in children with CMA. CONCLUSIONS Our study demonstrates slight disturbances in the profile of bone metabolism markers in growing children with CMA. The increase in RANKL level and decrease in OPG/RANKL ratio may contribute to intensification of bone resorption in these patients.