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Comparing 2,000 IU/day vs. 5,000 IU/day vitamin D supplementation

Posted on: March 29, 2012   by  John Cannell, MD


Dr. Terry Diamond and colleagues of St. George’s Hospital in New South Wales just published the first head-to-head comparison of 5,000 IU/day to 2,000 IU/day. Remember, the Food and Nutrition Board says 4,000 IU/day is the upper limit, but Dr. Diamond knows the pharmacology of vitamin D well enough to know that quite a few people will still have inadequate levels at 4,000 IU/day.

He recruited 30 patients with vitamin D levels less than 20 ng/ml and put half on 5,000 IU/day and half on 2,000 IU/day for three months. He measured a number of things, the most important of which was muscle strength.

Diamond T, Wong YK, Golombick T. Effect of oral cholecalciferol 2,000 versus 5,000 IU on serum vitamin D, PTH, bone and muscle strength in patients with vitamin D deficiency. Osteoporos Int. 2012 Mar 16.

After 3 months of 2,000 IU/day the vitamin D levels averaged 30 ng/ml (75 nmol/L), meaning about half the patients were still vitamin D deficient. Not so with the 5,000 IU/day group. The average vitamin D level was 45 ng/ml (114 nmol/L), right in the “natural range.” In addition, 93% of the patients had levels higher than 30 ng/ml compared to the 2,000 IU/day group, where only 45 % had levels above 30 ng/ml. Remember, one of the problems with daily dosing is that you must rely on the patient to take their medication. As an old GP, I am here to tell you not all patients take their meds; the ones that get me are the ones who look me straight in the eye and tell me something I know is not true.

In Dr. Diamond’s well-designed study, changes in grip strength compared to baseline were very significant, while the improvements in timed tests of sitting to standing and the 6-meter walk test also improved, but not significantly. What surprised me was that the improvements did not vary with dosage. That is, the 2,000 IU/day had the same improvements in grip strength as did the 5,000 IU/day, meaning muscle strength improvements are the most dramatic at changes in lower ranges of vitamin D levels. By that, I mean if your level is 5 ng/ml to start out and you get to up to 20 ng/ml, your percentage improvement in muscle strength will be much more dramatic than someone who went from 20 to 35 ng/ml.

I am glad to see Australians using daily dosing of vitamin D. Many of the “Stoss” doses, 100,000 IU/month or 600,000/year are not physiological, and are dangerous. Vitamin D was made every day in the skin of our ancestors and we should strive to replicate such dosing schedules. How much do we need? To quote Dr. Diamond, “This study demonstrates that the administration of oral vitamin D at 5,000 IU daily is superior to 2,000 IU daily for 3 months to treat mild to moderate vitamin D deficiency.”

5 Responses to Comparing 2,000 IU/day vs. 5,000 IU/day vitamin D supplementation

  1. Ian

    Lets hope the Australian Govt listens and changes their restriction on availability of vitamin D from 1000 IU to a higher level.

  2. [email protected]

    I would like to query your statement “Vitamin D was made every day in the skin of our ancestors”. There are many circumstances when this was not possible. I understand that Vitamin D3 is fat soluble and can be stored in the fatty tissues of the body. On this basis I take 50,000 iu every 10 days (5,000 iu per day). Is there any data that suggests this is harmful?

    • Brant Cebulla

      Ian, to date, there are no studies comparing 50K IU/week(or 10 days) to 5K/day. To answer directly, no, there is nothing to suggest this is harmful. There is a study that there is an increased risk in fractures in a much larger one-time dose.

  3. [email protected]

    No apparent change for taking the vitamin D monthly if your vitamin D level is less than 30 nanograms. For vitamin D levels higher than 50 nanograms the half life appears to drop dramatically – so you should not have longer than about 1 week between vitamin D supplements. The notional graphs which integrate what I have read in over 5,000 vitamin D studies are at: http://www.vitamindwiki.com/tiki-index.php?page_id=2475. I agree with Brant – there no evidence of any difference between 50K every 10 days and 5K daily – no matter what your vitamin D level is. Note, however, that most of the vitamin D co-factors are not stored in the body, so need to be taken approximately daily.

  4. [email protected]

    Many thanks, most helpful

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