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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

RCT: How much vitamin D is needed for optimal bone health?

While people think “bone health” when they hear “vitamin D,” the relationship between the two is not as clear as you might think. It’s been known for years that vitamin D prevents osteomalacia, but its effects on osteoporosis, fractures, and bone density are a bit murkier.

The current train of thought is that vitamin D can help prevent osteoporosis and fractures and improve bone density, but only when vitamin D is taken in adequate doses. Past trials have used doses as low as 400 IU and as high as 2000 IU, and its effects on bone health in these trials have ranged from no effect to modest beneficial effect. A meta-analysis by Professor Bischoff-Ferrari showed that vitamin D supplementation of greater than 800 IU/day has beneficial effects on fractures, while lower doses do not, perhaps explaining past mixed results.

A new randomized controlled trial led by Dr Helen Macdonald of the University of Aberdeen and recently published in the Journal of Bone and Mineral Research may further clarify past research.

This trial enrolled healthy women aged 60-70 living in vitamin D deprived Northeast Scotland for one year. Two-hundred sixty-three participants were randomized to take either placebo, 400 IU or 1,000 IU of vitamin D daily. No calcium was administered, but they reported good dietary intakes.

They measured bone mineral density at baseline and after a year. Here is what they found:

  • Bone loss at the hip was significantly greater in the placebo and 400 IU groups (each losing 0.6% bone mineral density after a year) compared to the 1,000 IU group, which essentially showed no change in bone density.
  • Bone mineral density at the lumbar spine was not statistically different after a year treatment in the groups (-0.5%, -0.2% and +0.2% for placebo, 400 IU vitamin D and 1,000 IU, respectively).
  • In the 400 IU group, vitamin D levels rose from 13.4 ng/ml to 26 ng/ml, while in the 1,000 IU group, levels rose from 13 ng/ml to 30.4 ng/ml.

The researchers concluded,

“Our findings are in agreement with the conclusions that more than 400 IU a day may be required to improve bone health and that the mean 25(OH)D concentration at which benefit occurs is greater than 30 ng/ml.”

This was some sorely needed research in the form of a randomized controlled trial showing that 400 IU/day of vitamin D is not enough for bone health and that 1,000 IU/day is likely the minimum you need for bone health. Furthermore, this study shows that a minimum level of 30 ng/ml is required for good bone health and that even a little bit lower at 26 ng/ml is not good enough to prevent bone loss.

This should offer good guidance to the public and health care professionals, looking for measures to help improve patient’s bone health.


Macdonald HM et al. Hip bone loss is attenuated with 1000 IU but not 400 IU daily vitamin D3: a 1 year double-blind RCT in postmenopausal women. Journal of Bone and Mineral Research, 2013.

  About: Brant Cebulla

Brant Cebulla was a staff member for the Vitamin D Council from May 2011 to April 2014. He has keen interests in nutrition and exercise.

5 Responses to RCT: How much vitamin D is needed for optimal bone health?

  1. Brant Cebulla says:

    There was also some interesting discussion in this paper that was a little off topic so I decided not to discuss in this blog. The discussion was on 25(OH)D levels, dosage and bone health in this study, and whether or not 25(OH)D accurately reflects clinical outcome compared to dosage.

    In this study 400 IU raised blood levels from 13 ng/ml to 26 ng/ml, while 1000 IU only saw a 20% greater increment in raising levels from 13 to 30 ng/ml, despite 1000 IU being a dose 2.5 times bigger than 400 IU. While diminishing 25(OH)D returns the higher and higher you supplement is well documented, what happens to all that extra vitamin D is not.

    In this study, the 1000 IU/day group saw such clinically and statistically better bone health outcomes compared to 400 IU/day, differences you would not anticipate by looking at the small margin between end of trial 25(OH)D levels, 26 ng/ml and 30 ng/ml. Thus the question arises, is the amount of vitamin D intake more important than 25(OH)D levels? To my knowledge, this study is the first to raise such question.

    The authors state it simply and best, “The discordance between the incremental increase in 25(OH)D between the 400 IU and 1000 IU vitamin D and effect on bone mineral density suggests that 25(OH)D may not accurately reflect clinical outcome, nor how much vitamin D is being stored.”

    Please note that this doesn’t change the way we approach or screen for vitamin D status, and thus is not clinically or publicly relevant for the time being.

    Other’s thoughts?

  2. RufusG says:

    There was a study done in Germany by Priemel et al that took 600+ cadavers from road accidents etc and compared bone quality and 25(OH)D Vitamin D

    They found that at least 30 ng/mL ( 75 nmol/L ) was required to achieve good bone quality

    Average weight people need 1,000 IU ( 25 micrograms ) per day to lift 25(OH)D by 10ng/ mL, so most people would need 2,000 IU ( 50 micrograms ) per day to avoid Osteoporosis

    I currently take 5,000 IU per day and my 25(OH)D is 56 ng/mL ( 140 nmol/L )

    My T-score is -0.6, where 0 to -1 is normal. Osteopenia is a T-score between -1 and -2.5 and Osteporosis is a T-score worse than -2.5

  3. Thanks for hopping in the conversation Rufus.

    For other’s reading, here is the study Rufus is referring to by Priemel/Amling: http://www.ncbi.nlm.nih.gov/pubmed/19594303

    And I highly recommend the artcile “Nutrition advice: The vitamin D-lemma” from the journal ‘Nature.’ http://www.nature.com/news/2011/110706/full/475023a.html The article discusses the IOMs use of Priemel/Amling’s data and the controversy in how they chose to use their data. A must read.


  4. Studies have shown that the PTH (Parathyroid hormone) is produced in significant amounts to keep serum calcium levels in the safe zone (at the expense of the bones) until the blood level of 25-hydroxyvitamin D level is 32 ng. In fact, that is how a level of 32 ng became regarded as the minimum normal. However PTH often continues to be produced until the level is 40 ng. So a strong case can be made that less breakdown of bone would take place if the level was at least 40 ng. As has been reported on this web site, levels of people near the equator in a more “natural” state is often at least 50 ng.

  5. Rebecca Oshiro says:

    Note to IOM: Here’s another RCT for you to consider next time you meet regarding this topic.