[Effect of vitamin D supplementation on serum 25-hydroxyvitamin D and bone turnover markers concentrations in vegetarian children].

PURPOSE: Vitamin D plays a key role in bone mineralization by regulating calcium and phosphate metabolism. Deficiency of this vitamin may lead to disturbances in bone metabolism as well as to osteopenia and osteoporosis.

AIM: 1. Assessment of daily intake of calcium and vitamin D in children on vegetarian diet. 2. Measurement of serum 25-hydroxyvitamin D and biochemical bone turnover markers levels in vegetarian children supplemented with calcium and vitamin D, before and after the intervention.

MATERIAL AND METHODS: We examined 35 prepubertal children on vegetarian diet who were divided into two groups: group A (without supplementation) and group B in which the children received daily 400 IU vitamin D3 and 500 mg calcium. Total serum calcium, phosphate, 25-hydroxyvitamin D and bone turnover markers were measured at start and end of the intervention.

RESULTS: Concentration of calcium and phosphate in serum of all tested children were within physiological range. The mean value of 25-hydroxyvitamin D at start of supplementation was low in both the vitamin D-treated group and in the controls (about 19 ng/ml). After 4-months supplementation, the vitamin D level was significantly higher in the vitamin D-treated group (38.3+/-8.5 ng/ml) than in the control group (13.7+/-5.3 ng/ml) (p<0.001). No statistically significant differences in bone formation (osteocalcin) and resorption (carboxy-terminal telopeptide of type I collagen, isoenzyme 5b of tartrate-resistant acid phosphatase) markers were observed.

CONCLUSIONS: The presented results indicate that in vegetarian children the daily dietary intake of vitamin D in the winter months is not sufficient to maintain adequate serum vitamin D concentration. Vitamin D daily supplementation increases vitamin D concentration in these individuals to the required levels.