Published on February 13, 2018

Whenever a study comes out that has questionable benefits for vitamin D the press reports it ad nauseam. In addition, the study below is almost always referenced. So, it is time to make sure we know the facts – not the hyperbole.

Where does this claim come from?

The paper from Bischoff-Ferrari, et al. reported on 200 home-dwelling men and women, over the age of 70, in Zurich, Switzerland. One purpose of the study was to assess whether vitamin D prevented falls in the elderly. The participants were divided into three groups which received monthly doses of vitamin D: 24,000 IU; 60,000 IU; or 24,000 IU of vitamin D3 plus 300 μg of calcifediol (25-Hydroxyvitamin D3).

Previous research studies on vitamin D and the elderly have found that a higher level of vitamin D prevented falls. But this study found differently. They found that while all groups increased their vitamin D levels, the higher vitamin D supplement groups, and those who achieved the highest 25(OH)D status, had more falls than the lowest group.

The authors did not state that vitamin D would not prevent falls or fractures

Bischoff-Ferrari stated in the discussion section of the paper,

the physiology behind a possible detrimental effect of a high monthly bolus dose of vitamin D on muscle function and falls remains unclear and needs further investigation.

Also, the conclusion of the paper was not that vitamin D would not help seniors, but that high monthly bolus dosing was not the right approach. Instead, the authors propose creating a new study using daily dosing.


In Defense of Vitamin D


While the paper from University Hospital Zurich received a lot of press, the results of the trial did not surprise us at GrassrootsHealth. More information is now known about the importance of daily dosing versus monthly dosing than was known at the time the study started. In order to prevent falls, you need strong muscles in addition to strong bones. For vitamin D to be effective in aiding muscle strength, stability and for general disease prevention, you need to take it daily – not monthly.

Think of it this way, what if you decided to run a marathon. How would you train? Would you build up gradually to a longer distance with daily (or maybe 4-5 times a week) runs? Or would you run once a month for 15-20 miles? Posing that question almost seems absurd, doesn’t it?


Effective vs. Ineffective Clinical Trials


Robert Heaney, MD, spent much of his career doing research on vitamin D and other nutrients. He published a paper with guidelines for nutrient studies. Below is a chart which lists the guidelines he recommends for an optimum nutrient study and an analysis of how this Zurich study measured up.

Nutrient Study GuidelinesBischoff-Ferrari Study
1. Basal nutrient status must be measured, used as an inclusion criterion for entry into study, and recorded in the report of the trial.QUESTIONABLE
Baseline 25(OH)D levels were measured and reported but were not used as inclusion criterion (58% were <20 ng/ml at baseline). Some analyses were limited to those with baseline levels <20 nmg/ml (but these analyses compared treatment groups, not achieved serum level groups).
2. The intervention (i.e. change in nutrient exposure or intake) must be large enough to change nutrient status and must be quantified by suitable analyses.DID MEET (WITH NOTES)
There were three groups: 24000 IU/month (about 800 IU/day; control group), 60000 IU/month (about 2000 IU/day), and 24000 IU/month and 300 microgram/month calcifediol. These dose amounts were large enough to produce a change in nutrient status.
Notes: While not measured with 25(OH)D, infrequent dosing of the parent coumpound, D3, may have influenced the results.
3. The change in nutrient status produced in those enrolled in the trials must be measured and recorded in the report of the trial.DID MEET
25(OH)D concentrations were measured and recorded at 6 and 12 months.
4. The hypothesis to be tested must be that a change in nutrient status (not just a change in intake) produces the sought-for-effect.DID MEET
While the hypothesis was that higher monthly doses of vitamin D would reduce the risk of functional decline, findings were also reported by achieved serum level.
5. Co-nutrient status must be optimized in order to ensure that the test nutrient is the only nutrition-related, limiting factor in the response.QUESTIONABLE
Data about other nutrients do not appear to have been collected or reported (e.g. calcium, magnesium, vitamin K, etc...).


Monthly High-Dose Vitamin D Treatment for the Prevention of Functional Decline
Heike A. Bischoff-Ferrari et al.
February 2016
Read Paper

Taking Vitamin D May Not Reduce Risk of Falls
Time Magazine online offers summary of paper
January 4, 2016
Read Article

The Role of the Parent Compound Vitamin D with Respect to Metabolism and Function: Why Clinical Dose Intervals Can Affect Clinical Outcomes
Bruce W. Hollis and Carol L. Wagner
Medical University of South Carolina
Journal of Clinical Endocrinology & Metabolism
December 2013
Read Paper


Guidelines for optimizing design and analysis of clinical studies of nutrient effects
Robert P. Heaney, MD
Creighton University
December 2013
Read paper