A new meta-analysis from New Zealand reports that the use of vitamin D supplements for osteoporosis prevention in healthy adults seems to be inappropriate, as it does not improve bone mineral density. In contrast, experts say that increased vitamin D intakes have clearly shown to significantly reduce fracture risk.
The meta-analysis included 23 randomized controlled trials – involving 4,082 healthy adults with an average age of 59 years – which examined the effects of vitamin D supplementation for an average period of two years on bone mineral density (1). The analysis showed that the studies did not identify any effect on bone mineral density (BMD) for participants who took vitamin D, apart from a small but statistically significant increase in bone density (0.8%) at the femoral neck.
The researchers concluded that the widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate. However, maintenance of vitamin D stores in the elderly combined with sufficient dietary calcium intake (800–1,200 mg per day) remains an effective approach for prevention of hip fractures (2).
Experts criticized that the analysis only evaluated the effect of vitamin D on BMD – a surrogate parameter for predicting the risk of future bone fractures or diagnosing bone loss and osteoporosis. A much more im- portant indicator for vitamin D efficacy is fracture risk: several randomized controlled trials have shown that adequate vitamin D intakes significantly reduce hip fracture risk (up to 30%) (3). Latest research indicates that the positive effect of vitamin D on muscle strength is a key mechanism in prevention of falls and frac- tures (4).
An estimated 8.2 million women over the age of 55 have osteoporosis in the US (5). According to the Inter- national Osteoporosis Foundation, osteoporosis causes more than 8.9 million fractures worldwide annually. The combined lifetime risk of hip, forearm and vertebral fractures is equivalent to the risk of cardiovascular disease. Vitamin D is needed for calcium absorption and to maintain strong bones. A deficiency in one, or both of these micronutrients, is thought to increase the risk of osteoporosis. Vitamin D deficiency and insuffi- ciency are highly prevalent in healthy adults worldwide. Depending on the classification used, deficiency occurs in up to 55% and insufficiency in up to 78% of adults (6). Many scientists describe current policies for vitamin D supplementation and fortification as inadequate and ask for guidelines to improve vitamin D status.