Vitamin D deficiency and effect of vitamin D supplementation in children on vegetarian diet

Many people in the world (particularly at northern latitudes) are currently vitamin D deficient. Children on vegetarian diet are at great risk of deficiency of this vitamin, especially in wintertime. Vitamin D plays a key role in bone mineralisation by regulating calcium and phosphate metabolism. Therefore deficiency of this vitamin may lead to disturbances in bone metabolism.

We studied 35 prepubertal vegetarian children who had been referred to the Institute of Mother and Child in Warsaw for dietary consultation. Dietary constituents were analyzed using the nutritional program Food2®. Total serum calcium, phosphate, 25-hydroxyvitamin D and biochemical bone turnover markers were measured. All children were allocated to one of two groups: group A (without supplementation) and group B that received daily 400 IU vitamin D₃ and 500 mg calcium for 4 months in wintertime. In all vegetarian children mean daily energy intake and the percentage of energy from protein, fat and carbohydrates were adequate. The daily intake of phosphate was correct but that of calcium and vitamin D were below (about 40%) the recommended range. The mean value of serum 25-hydroxyvitamin D at baseline was low (about 19 ng/ml) in both studied groups. After 4-months supplementation vitamin D level was about 2-fold higher in the vitamin D-treated group than in the children without supplementation (30.1+/-8.5 ng/ml vs 13.7+/-5.3 ng/ml, p<0.001). There was slight (about 5-10%) increase in bone formation and resorption markers. Concentrations of calcium and phosphate in serum of all tested children were within the physiological range.

The presented results indicate that in vegetarian children dietary intake of vitamin D is not sufficient to maintain adequate serum vitamin D concentration. In the wintertime a daily supplementation of vitamin D₃ and calcium increased vitamin D concentration in these individuals to the required levels.