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Do vitamin D supplements have an effect on bone health?

Lots of people take vitamin D supplements to keep their bones strong as they age, advice that is pushed by legitimate organizations, like the National Osteoporosis Foundation. Research has looked at the effect of vitamin D supplements on bone density, a measure of bone health.

I’ve written extensively about vitamin D supplements, and its effect on health is decidedly mixed. I think the best that can be said is that if you have low blood levels of the vitamin, it is medically justified to take the supplements to keep vitamin D at appropriate levels.

But let’s take a look at a study that examined whether vitamin D supplements had an effect on bone density.

black and white bones hand x ray
Photo by Pixabay on

Research study on vitamin D effect on bone density

In a systematic review and meta-analysis published on 10 October 2013 in the Lancet, Ian R Reid, MD, Faculty of Medical and Health Sciences, University of Auckland, New Zealand, and colleagues examined previous clinical trials involving vitamin D supplements to determine if they helped improve bone density, a critical measure of bone strength and health.

The systematic review included 23 previously published studies (comprising a total of 4082 participants, 92% women, average age 59 years) who received vitamin D supplementation over an average of 23.5 months. Bone mineral density was measured at one to five sites (lumbar vertebrae, femoral neck, total hip, trochanter, total body, or forearm) in each study.

The studies included in the review had differing vitamin D supplementation regimens. The vitamin D dosages, as well as the length of the treatment, varied across. On average, 500 IU (international unit, with each unit being the biological equivalent of 0.025 μg cholecalciferol/ergocalciferol) was the daily dose in six of the studies, 500-799 IU was used in four studies, and 800 IU or more was used in 13 studies.

Across all of the studies, 70 tests of statistical significance were performed. Out of those 70 studies, the researchers found the following:

  • Six had findings of significant benefit to bone density from vitamin D supplements.
  • Two showed significant detriment of vitamin D supplements.
  • The remaining 62 studies showed no significant benefit or detriment of vitamin D supplementation.
  • Of all the studies, only one showed a benefit at more than one bone site.
  • More supplementation did not show any benefit, so there was no dose-response effect.

The researchers determined that vitamin D supplements did not usually increase bone density for people who already had normal levels of vitamin D. Although bone density did improve in the femur, the longest and heaviest bone in the human skeleton in two studies, all other bones did not exhibit a higher density after vitamin D.

Most importantly, of the studies that did report improvement in bone density, the finding was not significant enough to prevent a bone from fracturing after a fall. Surprisingly, the researchers also discovered that doses of less than 800 IU per day were more effective for improving bone density in the spine.


The researchers concluded that “continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate.”

In other words, the evidence does not support the hypothesis taking vitamin D supplements provides a benefit of increased bone density in individuals who already had healthy levels of vitamin D–supplementing with vitamin D was not necessary for most adults over the age of 55. However, the researchers did recommend that healthcare providers should target individuals who may not be getting sufficient vitamin D naturally, such as exposure to sunlight or diet, with either vitamin D supplementation or sunlight therapy. 

The researchers did not find any evidence that excess supplementation of vitamin D would have any effect on bone health. As I usually say in this type of research, get your vitamin D levels tested by your physician, and if it’s low, take the appropriate amount of supplement to get your blood levels to normal. But taking more is not going to do anything beneficial.


Michael Simpson

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