Maximizing the build-up of bone during the highly important pubescent years is seen as one of the two best ways to reduce the risk of osteoporosis later in life. About 35% of a mature adult's peak bone mass is built-up during puberty.
The other approach is to boost bone density in high-risk post-menopausal women by improved diet or supplements.
According to new data published in Bone, daily doses 1,400 IU or 14,000 IU of vitamin D for one year produced significant increases in bone mass in the hip of adolescent girls, but not boys.
“To our knowledge this is the first to demonstrate a measurable positive effect of vitamin D supplementation on bone geometry in girls but not boys, during a critical time of growth and peak bone mass accrual,” wrote researchers from the Calcium Metabolism and Osteoporosis Program in Lebanon, the American University of Beirut, Toronto University, and Johns Hopkins School of Medicine.
“It also provides insights into pathways for such effect, which may in part be explained by the beneficial effect of vitamin D supplementation on lean mass.
“If confirmed and sustained into adulthood, these observed changes would be anticipated to translate into a reduced risk of hip fractures in elderly years.”
The researchers, led by Ghada El-Hajj Fuleihanm, recruited 167 girls and 171 boys (average age of 13) to participate in their double-blind placebo-controlled trial. The adolescents were randomly assigned to receive placebo, 1,400 IU or 14,000 IU of vitamin D for one year. Bone parameters were measured using dual energy X-ray absorptiometry (DXA) technology.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol.
Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Vitamin D deficiency (less than 20 ng/mL) can cause a number of health issues, including rickets and other musculoskeletal diseases. Recently, data has also suggested that vitamin D deficiency and vitamin D insufficiency (between 21-29 ng/mL) may be linked to cancer, autoimmune diseases, infectious diseases, type 2 diabetes and cardiovascular disease.
Results of the study showed that girls experienced increases in bone mineral density of 7.9% and 6.8% in the low and high dose vitamin D groups, compared with 4.2% in the placebo group. In addition, the so-called buckling ratio at the narrow neck part of femur was strengthened by 6.1% and 2.4% in low and high dose groups, respectively, compared with 1.9% in the placebo group.
On the other hand, boys did not show any significant benefits in any parameters measured, said the researchers.
“The lack of an apparent effect on bone geometry [in boys] may possibly be due to the higher 25(OH) levels at study entry in boys, and possibly the powerful effect on bone mass and structure of a larger lean mass and activity level than in girls,” explained the researchers.
“Alternatively, other possible explanations for the observed sexual dimorphism may include the divergent effect of sex steroids on bone mass, micro-architecture, and muscle, the delayed timing of puberty in boys compared to girls, and the delay in changes in bone geometry in this gender compared to girls.”
Volume 56, Issue 2, Pages 296–303, doi: 10.1016/j.bone.2013.06.020
“Effect of vitamin D replacement on hip structural geometry in adolescents: A randomized controlled trial”
Authors: Al-Shaar L, Nabulsi M, Maalouf J, El-Rassi R, Vieth R, Beck TJ, El-Hajj Fuleihan G.