A new look at an old randomized controlled trial has found that vitamin D supplementation during adolescence positively affects bone geometry of the femoral neck.
The randomized control trial took place in Beirut in 2001 and 2002. One hundred sixty seven girls (mean age 13.1 years) and 171 boys (mean age 12.7 years) were randomly assigned to receive either a weekly placebo pill or a weekly vitamin D pill of 1,400 IU or 14,000 IU for one year.
Initially, researchers were interested if vitamin D influenced bone mass density. They found that it did, for both the low dose and high dose groups, but only in the girls.
However, no one to date had looked at whether the vitamin D supplementation affected the geometry and structure of bone.
Bone mass accrual during adolescence is important. In general, the more mass accrued during this development stage in life, the more likely you are to have healthy bones later in life. The development of good bone geometry, in addition to development of good bone mass density, is essential in bone mass accrual.
In this analysis, researchers found that once again, vitamin D supplementation affected the girls but not the boys.
For girls, vitamin D supplementation reduced the buckling ratio at the narrow neck of the femur. It also improved the cross sectional area of the intertrochanteric and outer diameter of the shaft. There was no statistically observed benefit in those who took the 14,000 IU of vitamin D compared to those who took the 1,400 IU; both vitamin D groups fared equally well compared to the placebo group.
The researchers concluded,
“To our knowledge this (study) 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… If confirmed and sustained into adulthood, these observed changes would be anticipated to translate into a reduced risk of hip fractures in elderly years.”