Does vitamin D actually help your bones?

Osteoporosis, a disease in which bones deteriorate or become brittle and fragile due to low bone mass and bone tissue loss, occurs quite frequently in older people. In fact, 16.7%^[1] of people over the age of 65 are reported to have osteoporosis of the lumbar spine or neck of the femur. Reductions in bone mineral density due to osteoporosis increase^[2] the risk of fractures from falls in elderly people.

Vitamin D plays a role in regulating^[3] bone mineral density and vitamin D deficiency leads to malformation of bone tissue. The details of vitamin D’s role are laid out in Figure 1. In extreme cases, vitamin D deficiency can lead to rickets^[4] in children or osteomalacia in adults. The former refers to impaired mineralization at the places where bones grow during development, whereas the latter is a deficiency in hardening of the bone matrix. Both are often due to inadequate vitamin D. Given its role in regulating bone metabolism, vitamin D supplementation has been investigated as a strategy to improve bone mineral density and reduce the risk of fracture. To date there have been myriad randomized controlled trials with some showing a reduced fracture risk, and others showing no benefit.

Given the conflicting nature of the findings from randomized controlled trials, several meta-analyses were conducted to consolidate the conflicting experimental evidence. However, there have been 45 more randomized controlled trials conducted since the last review was done, which increases the explanatory capacity of the meta-analytic approach and also allows for trial sequential analysis^[5], which lets one see how likely an effect is, and how much more evidence might be needed to come to firm conclusions. The present study was a systematic review, meta-analysis, and trial sequential analysis examining the effect of vitamin D supplementation on fractures, falls, and bone mineral density in adults over the age of 18.

Vitamin D plays a key role in regulating bone metabolism and bone mineral density. To date, dozens of randomized controlled trials have examined the effect of vitamin D supplementation on fractures and bone mineral density in adults. The present study was a systematic review, meta-analysis, and trial sequential analysis examining the effect of vitamin D supplementation on fractures, falls, and bone mineral density in adults over the age of 18.