Vitamin D supplementation had no statistically significant effects on total body bone mineral content or on bone mineral density of the hip or forearm .
It is unlikely that vitamin D supplements are beneficial in children and adolescents with normal vitamin D levels .
OBJECTIVE To determine the effectiveness of vitamin D supplementation for improving  bone mineral density in children and adolescents and if effects vary with factors such as vitamin D dose and vitamin D status .
Wintertime Vitamin D Deficiency in Male Adolescents: Effect on Parathyroid Function and Response to Vitamin D3 Supplements
Abstract : The first part of this study consisted of an 18 month follow-up of the vitamin D status and parathyroid function in a group of 54 French male adolescents , aged from 13 to 16 years old and all pupils of a jockey training school . During the 18 month period four samplings were made , one every 6 months . The first was during September of the first year , the second and third during March and October of the second year , and the last in March of the third year . Therefore we had two main periods : summer and winter . The summer 25-hydroxyvitamin D ( 25(OH)D ) concentrations were higher ( 71.6 ± 19.9 and 52.4 ± 16.5 nmol/l ) than the winter ones ( 20.4 ± 6.9 and 21.4 ± 6.1 nmol/l ) . Conversely , the winter intact parathyroid hormone ( iPTH ) serum levels ( 4.18 ± 1.18 and 4.11 ± 1.35 pmol/l ) were higher than the summer ones ( 2.44 ± 0.82 and 2.71 ± 0.71 pmol/l ) . At the two winter time points the 25(OH)D concentrations were lower than 25 nmol/l ( 10 ng/ml ) in 72 % ( 2nd year ) and 68 % ( 3rd year ) of the adolescents . In the second part of the study we tried a vitamin D3 supplementation procedure design ed to maintain the 25(OH)D and iPTH postsummer serum levels throughout the winter . Pairs of male adolescents matched for height , weight and Tanner pubertal stage were r and omly assigned to either vitamin D3 supplementation ( 2.5 mg , i.e. , 100 000 IU ) administered orally at three specific periods ( end of September , November and January ) or no vitamin D3 treatment ( control subjects ) . Blood was collected just before the first intake of vitamin D3 and 2 months after the last intake ( March ) . The control subjects had blood drawn at the same time points . In the vitamin D3-treated subjects , the concentrations of 25 (OH)D ( 55.3 ± 11.5 nmol/l ) and of iPTH ( 3.09 ± 1.16 pmol/l ) in March and September ( 53.8 ± 12.3 nmol/l and 2.75 ± 1.26 pmol/l ) were not significantly different . In the control subjects , March 25(OH)D levels ( 21.0 ± nmol/l were low , with values below 25 nmol/l in 78 % of subjects , and iPTH concentrations ( 3.97 ± 1.08 pmol/l ) were significantly ( p<0.001 ) higher than in September ( 2.91 ± 0.81 pmol/l ) . The constant vitamin D wintertime deficiency and wintertime rise in iPTH in adolescent French males throughout puberty has been demonstrated . In adolescents with low dairy calcium intakes , the vitamin D3 treatment was sufficient to maintain 25(OH)D concentrations at their summer levels throughout winter and to prevent an excessive wintertime rise in iPTH levels
Vitamin D supplementation had no statistically significant effects on total body bone mineral content or on bone mineral density of the hip or forearm .
It is unlikely that vitamin D supplements are beneficial in children and adolescents with normal vitamin D levels .
OBJECTIVE To determine the effectiveness of vitamin D supplementation for improving  bone mineral density in children and adolescents and if effects vary with factors such as vitamin D dose and vitamin D status .