Let's look at a recent study that claimed Vitamin D DOES NOT HELP with fractures/falls in older people. Sounds like something funny was going on here - so let's explore a little.
Now, when a critical agent for the human body is being investigated, how do you decide the dosage regimen? In this study it is "Vitamin" D3 being applied.
Well first you'd look at the half-life of the specific supplement in humans, wouldn't you? That's approx. 1 day in the case of D3.
Then you'd look at the daily maximum recommended dose to avoid toxicity - that was 2,000 IU when this study was done.
Then you'd look at the evolutionary appropriate dosing, to make sure you don't overload the species' enzymatic and other systems, as that would utterly invalidate your experiment (in this case a few thousand IU would be reasonable DAILY - because there are strong emerging hypotheses that suggest the very sinusoidal seasonal change in D is itself a problem, since we left the relatively constant daily dosage achieved in equatorial regions ~20k years ago).
So I guess you'd give maybe 2000 to 3000 IU/day max over the 5 years of the study, that would be a reasonable approach, right?
Or........you COULD give 500,000 IU in one massive injection once a year. That's not a typo there by the way. Excuse me? I kid you not: 500,000 IU was delivered in one injected dose each year, and the peak of fractures occurred in the few weeks following this depthcharge-like bolus. Turn the dial up to 11, that ought to do it - click link to study below:
And see below see snapshot of result - the only significant finding were spikes in the 3 months following the enzyme-busting bomb - until next year, when another salvo pours in (would be really interesting to see 1st month after the depthcharge dose, not just 3-month - the main graph shown at the end seems to show some blips in single months following the massive injection)
And see below overall trends - looks like the first couple of annual grenades shook them goodo, with the subsequent firecrackers lighting them up for a month or two also. How would this experimental design even get past an initial brainstorming session? (Check out the falling numbers of participants also...)
Note: I first saw this kind of inexplicable approach during Prof Vieth's lecture: https://www.youtube.com/watch?v=MIDWA9-cGdY , and was irked into writing this post when I came across this today, which referenced the offending study as supporting evidence of higher D being "bad" - it's no wonder confusion reigns.... http://www.medpagetoday.com/PrimaryCare/DietNutrition/48823