The effects of vitamin D supplementation on bone density in vitamin D insufficient teenagers: randomised controlled trial

This study is investigating whether vitamin D supplements can improve bone development in teenagers who have mildly to moderately low vitamin D levels. Building strong bones in adolescence helps reduce the risk of osteoporosis and fractures later in life. This is a placebo-controlled trial, meaning some participants will receive vitamin D and others will receive a sugar pill. You may be eligible if: - You are between 15 and 17 years old - You are generally healthy - You have mild to moderate vitamin D deficiency (blood level between 12.5–50 nmol/L, measured in July–October) - You do not have severe kidney problems, malabsorption conditions, or signs of rickets - You are not pregnant or breastfeeding You may NOT be eligible if: - Your vitamin D level is severely low (below 12.5 nmol/L) - Your vitamin D level is already normal (50 nmol/L or above) - You have severe kidney disease, malabsorption, pregnancy, or lactation - You have clinical signs of rickets Talk to your doctor about whether this trial might be right for you.