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RCT: Vitamin D induces short-term increase in muscular power

Posted on: October 12, 2012   by  Brant Cebulla


A recent randomized controlled trial led by Andres E. Carrillo from Purdue University has found that vitamin D supplementation may help peak power in the short term, but perhaps not in the long run over the course of a workout program.

The researchers split 23 participants into two groups, ten in the vitamin D group (5 females, 5 males) and thirteen in the placebo group (7 females, 6 males). The mean age was 26 years old, with participants weighing a mean of 191 pounds in the vitamin D group and 202 pounds in the placebo group. The percentage body fat in both groups was a little over 40 percent, categorizing the participants as obese. The vitamin D group received 4,000 IU/day, while the control group received a placebo.

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9 Responses to RCT: Vitamin D induces short-term increase in muscular power

  1. Ron Carmichael

    Brant – Figure three in the study pdf (http://www.clinicalnutritionjournal.com/article/S0261-5614(12)00181-1/abstract) demonstrates that not only did the short-term period use of vitamin D result in a steeper slope(faster improvement compared to placebo) for “peak muscle power”, but that those on even an ineffective dosage of vitamin D continued to “be ahead” of the placebo group throughout the duration of the study, on a scale of 0 to 150 where the D group was at ~150, and the placebo group was at ~100. It sounds to me like the authors expected a continual and ever-increasing benefit , an upward trend of the entire plot, from taking a small amount of vitamin D that in their own words resulted in a blood level that was less than HALF of what they expected, and when they did not see it they chose to characterize everything in a negative light.

    They COULD have said, “initially the vitamin D group gained better peak muscle power than placebo, and had a wider range of increase at 4 weeks than the placebo, and thereafter continued after on a roughly parallel but higher level of peak muscle power throughout the study, finishing with a statistically higher level than the placebo group at 12 weeks” , instead of implying a failure of vitamin D. One might detect a certain bias with their choice of interpretation (as with mine, I confess). I am also confused as to why, with a 50% greater (150 is 50% greater than 100) power value, they chose to say there was no difference? I do not see where they define the Y Axis of “W” – watts of power – I am probably missing it somewhere in the text ?

    Of note also is that the determination of strength was that they stopped everyone at 15 reps, except where the subject couldn’t reach 15. So anyone of more fitness was inhibited in achieving better improvement. “I can run 4 miles in 20 minutes, but you are only going to let me run 50 yards, and let’s see if I improve in strength”… I have to wonder whether any of those that could not make 15 reps on day one were able to on week 12? This is blatant data flattening.

    What I see in this study is that the authors significantly underestimated the inertial effects that excessive weight has upon the systems of the human body, not only with their vitamin D “failure to therapeutic levels” .

    I am profoundly disturbed by the bottom-line takeaway I perceive they are telling us in this study, that 12 weeks of exercise did not make ANY difference in any of the factors they chose to monitor: lean mass accumulation, muscular strength, or glucose tolerance . So in this study I might conclude that exercise is useless while they conclude is that vitamin D is barely of significance? It is also a shame that they did not monitor these subjects with regard to any type of infection while they were counting the packets of sunscreen that the subjects did not use. Yet another example of preconceptions in protocol design retarding the advancement of meaningful science.

    • Brant Cebulla

      Ron, I think the authors are probably a little disappointed about the execution and results. Mainly that they were unable to raise vitamin D levels as high as they would have liked and that the workout program “masked” their results, at least statistically speaking. As for the lifting program they used, I think there are probably lots of ways to execute a program and that they all have downfalls. How would you have designed it?

      Agreed, a look at that graph would tell any weightlifter that it’s better to take vitamin D and stay on that vitamin D through the course of their workout program, though this was not statistically significant. I’m sure the authors would have been ecstatic if it were statistically significant. Even without the graph, I think the statistically significant finding — vitamin D improves peak power after 4 weeks — is enough to encourage weightlifters and people trying to get back in shape to use vitamin D as part of their program.

      I thought the language and rhetoric was pretty careful in the paper, no? Seemed like they weren’t trying to make much of anything, either way. Who knows, maybe they did want to talk about how peak power was trending in favor for vitamin D after 12 weeks and the reviewers scratched it out.


  2. Ron Carmichael

    My ideal study, Brant? I’ve never created a study and as a college pharmacy student only participated in one 🙂 Off the cuff…..

    I would rely on the relatively new methods of performing comprehensive retrospective analysis with computer programs, algorithms, to take a large quantity of subjects gathering instead prospective data, with less lofty conclusion goals. Quantity defines its own quality to a degree.

    You know of huge longterm studies of nurses on baby aspirin, for example, that spanned many years. Meaningful conclusions came from these kinds of studies. I think we need such a type for vitamin D3.

    Activate the study on November 1 in the northern hemisphere and target 8 states that have representative proportions of ethnic groups similar to the overall average across the US with regard to the four or five largest ethnic groups. Not saying other groups do not desperately need the same kind of evaluation, but I think that would be phase two, once the problems and shortcomings of this study are identified so that a more precise/accurate protocol can be used. The states are each further north than the previous – say, Florida, Nebraska, Oregon, and Alaska – perhaps increase with some eastern seaboard states for “balance” – N Carolina, Illinois, New York, Maine.

    By volunteers willing to purchase their “special” vitamin D3 (say the BioTech D3PLUS which has more than just D3) on their own at a set, special lower-than-retail price from a particular single source, accept 10,000 adults employed full-time (for chronicity stability – they have routines of life habits that stabilize the substrate) between 18 and 60, who remain under the care of their primary care physicians – both of whom agree to a user-friendly protocol guaranteeing anonymity of the patient but sharing of fundamental assets of the patient’s file. It is critical that the first stage establishes just how much D3 is needed for each subject to reach at least 50 ng/ml. The dr. will have to assess tan lines to estimate (against a contrast card) the degree of sun exposure for the skin type (presuming that we don’t have many nudists in the study who don’t have tan lines). The card also provides a way to rate the untanned skin tone type, a datapoint under consideration. The patient gets a 25(OH)D test in the first week of November, and each month thereafter.

    For December, for every 10 ng/ml the subject is below 50 ng/ml, the protocol the dr. follows requires an increase in daily D3 oral dosage of 1,000iu per hundred pounds of weight, rounding up in all cases where a fraction of 1000 occurs.

    In January, if the blood level still fails, the subject is directed to increase based on a proportional formula based on the response seen to the first adjustment. Simply, if 1k/100 lbs//day got them 1/2 way up from the level on day 0 and day 32, the physician directs the subject to go to 2k/100 lbs//day. Overshooting 50 ng/ml is recorded but not considered problematic unless it exceeds 70 ng/ml.

    During the study, the physician uses a web-based form to log specific disease states, and the physician’s subjective assessment of severity of condition of that DZ. The form displays what the dr. chose (say on a scale of 1 to 10 where appropriate, or else the insulin dose required and the A1C value, or the lipid levels, what ever lab values the physician uses to monitor that patient anyway, are gathered into the database. In most cases this entry will probably be performed by staff in the dr’s office, so I am concerned about compliance in data entry. It may be that the protocol outlines that only the two / three “worst” conditions are tracked.

    In addition to the 2 or 3 chronic conditions being treated/monitored, the advent of a new condition including especially acute types such as “flu”, respiratory infections, ear infections, fevers of undetermined origin, bowel problems, etc. should be documented.

    The college pharmacy students I would enlist to run the database coding and compilation for the information would proactively call the drs to help them keep up to date.

    Perhaps a carrot for the drs would be a guarantee to share information at each month – simply a statistic of what is needed to get patients to 50 ng/ml for their particular state (and for the other states as well). This is a critically important feedback tool to help all practitioners get their subjects to 50 ng/ml as quickly as possible.

    And also as data builds to the point where trending can be performed, those trends, regardless of what they are, are labeled and shared as “non-statistical” preliminaries. I would expect the first such “bulletin” be sent out at 5 or 6 months.

    As for the placebo section – I think the placebo aspect would simply be that the physician ask patients 1) do they take vitamin D3, do you take a multivitamin? if they answer no to both, and say yes to would they like to provide their blood levels of 25(OH)D for “the next 6 months”, and follow them in a similar way with reporting, and ask the patient to maintain their habits (no D3, no multivits). Dr. performs same short form online evaluation and information is pipelined the same way.

    I have absolutely no idea of how this would be paid for. Even the volunteer nature, involving pharmacy students and an open appeal to patients, who will be allowed to purchase low-cost D3Plus from one company who then receives the publicity of supporting science and the advancement of health. I think the college of pharmacy at my alma mater, who work in concert with a large health science center where I also performed rotations in clinical and drug information capacities, could be one “center” as part of a “multi-center” approach to this – each state to have one college of phr. participating on the back end drudge work.

    GOAL: finally. I think the best that can be hoped for is a better awareness of just how much D3Plus does what for the average American, whether getting natural levels of 25(OH)D has any effect on weight, existing disease states, incidence of acute DZ. (and more that better minds will be able to figure than I can).

    It occurs to me that it would be better to identify and limit consideration to say, TEN diseases that have already been shown to be responsive to D3, in order to add data to the conversation already in progress. Any of this stick to the wall or is it absurdly naive to think something so lax could pass review in today’s climate?

  3. Ron Carmichael

    Incidentally, I would have the college students set up auto emails, tweets, and texts to the patient population (where appropriate) to remind them that “we are counting on you! Have you taken your D today?….

  4. Brant Cebulla

    Ron, very thorough! There was a nicely designed study of late that titrated weekly doses so that all participants in vitamin D arm maintained levels of 70 ng/ml. The participants were people with pre-diabetes.

  5. Brant Cebulla

    Also, I know you coach and is line with the reminders that you refer into in your follow up comment — check out this App: https://www.remind101.com/

    Pretty cool tool. I’m unfamiliar if researchers are starting to use similar tools.

  6. Brant Cebulla

    Lastly, I found this humorous and was meaning to mention it in this thread right away:

    One participant dropped out, complaining about poor reaction and ingestion problems in taking the intervention pills. Turns out, the person was taking a placebo! I wonder if they ever found out that they reported adverse reactions to taking a placebo!



  7. [email protected]

    Re Brant Cebulla October 19, 2012, vitamin D increases testoserone levels in men, as well

    as increasing human growth (IGF) levels in both sexes. Both hormones have an effect on

    human strength. Maybe we are crediting vit D for actions that are really caused by Ds

    stimulating other hormones. Regards, Millard Ferguson

  8. [email protected]

    Millard makes an interesting point–worth further investigation (IMO).

    To sunny days,

    Rita C. Umile

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