Vitamin D3 a "Fat Synthesizer"!? Rodent Study Shows +33% Increased Fat Deposition in Vitamin D3 Supplemented Mice.

Illustration 1: Experts will recognize from looking at these Oil Red O-stained longissimus dorsi slices of mice on a normal and a vitamin D3 supplemented diet that supplemental (! not vitamin D from the sun !) "vitamin D3 can be used a s a fat synthesizer and meat tenderizer in meat-producing animals". (img in illustraton from Choi. 2011)
I have been railing against the current vitamin D hype for months now. In that, I have at no point in time implied that "backfilling" depleted vitamin D levels via supplementation could not be beneficial (or at least not harmful), nor have I at any time excluded that vitamin D3 supplementation (even if you are in the "normal" range) could have its merit (cf. vitamin D3 + HMB). What I have done though, was to point at the lack of controlled studies that would support any of the benefits supplemental vitamin D3 is currently hailed for all over the Internet. This amazes me, because the very same "gurus" who are all over the vitamin D bandwagon have lately (just like me) discarded the data from the Iowa Women's Health Study as "unrealiable" and "non-significant" epidemiological bullshit (which is exactly, what I think, as well). When it comes to vitamin D, however, they throw all their concerns on the validity of epidemiological data over board and worship their vitamin D3 pills like a golden calf.

But let's get to the facts, before I get tarred and feathered, again... In the latest issue of the Journal of the Science of Food and Agriculture Hyuck, Choi and Kyuho Myung published a paper that investigated the use of vitamin D3 supplements to fatten animals (Choi. 2011). Now, you may think "How stupid is that, everyone knows that vitamin D will make you lean out!", but as I've pointed out several times within the last weeks, high vitamin D levels may correlate with a lean body composition; however, studies that would show that supplementation of the latter would induce respective changes in body composition in the absence of prior deficiency (and we are talking about the standard reference range with a lower limit of 10ng/mL, here) simply do not exist... but I am digressing again.
Figure 1: Composition of the diet (large figure) and respective vitamin D3 content (small figure) of the diets of the control and the supplement group in the study.
As you can see in figure 1 both groups (2x N=10) of 6 weeks-old male C57BL/6 mice were fed identical chows (AIN93G; cf. figure 1, large), varying only in their vitamin D3 content (1IU in the control group, 10IU in the supplemented group). In human terms this would be like switching from your common western low vitamin D diet with roughly 800IU to taking a 8.000 IU supplement, each day - something I suppose many of you may have done lately!?
Figure 2: Body fat (in g; large figure) and respective serum 1α,25-(OH)2 -vitamin D3 levels (in µg/mL; small figure) after 3 weeks on control or vitamin D3 supplemented diet (data calculated based on Choi. 2011)
As figure 2 shows, this 10-fold increase in dietary vitamin D would only be advisable if you were a "sumo mouse" who has to make weight for the next competition. A plus of +33% in total, +29% in unaesthetic subcutaneous and +25% in unhealthy visceral fat (all statistically significant with p<0.022, p<0.032 and p<0.043) is not what you would expect of the "greatest vitamin of all time" - would you? And while the vitamin D3 mice also gained some more body weight, those changes were statistically non-significant, so that - as the scientists state - vitamin D3 turned out to be an ideal "fat synthesizer and meat tenderizer".
Figure 3: Cytokines, UCP-2 and PPAR-gamma expression in mice after 3 weeks on control or vitamin D3 supplemented diet (based on Choi. 2011)
In that, vitamin D3 works it "fat synthesizing" magic by increasing the inflammatory cytokines TNF-alpha and IL-6 and decreasing the muscle anabolic (Busquets. 2005) and fat catabolic cytokine IL-15 (Carbo. 2001; Alvarez. 2002), as well as the uncoupling protein UCP-2 while ramping up fat storage via increase PPAR-gamma expression (cf. figure 3).

Now obviously, this is just another rodent study and we cannot say how and if the results will translate to humans, but it is a controlled study and it investigates the effects of supplemental vitamin D3 which is something you cannot say of the "scientific backbone" of the current vitamin D3 craze... and now tar and feather me like a child who has just been bereaved of his favorite toy, if you will ;-)
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