A new randomized trial shows it can reduce the risk of cancer, while increasing the risk of heart disease.
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Imagine if you will the great Cathedral of Our Lady of correlation you walk through the Majestic oak doors depicting the link between ice cream sails and shark attacks past the rose window depicting the cardiovascular benefits of red wine and down the aisles frescoed and dramatic images showing how Facebook
Usage is associated with less life satisfaction and then you reach the altar the holy of holies where emblazoned in shimmering pyite you see the patron saint of this church vitamin D yes if you’ve watched this space you know I have little truck with the wildly popular supplement in all of
Clinical research I believe there is no molecule with stronger data for correlation and weaker data for causation low serum vitamin D levels have been linked to higher risks of heart disease cancer Falls covid dementia SEI and others and yet when we actually do randomize Trials of vitamin D supplementation the thing that can
Prove that the low level was causally linked to the outcome of Interest we get negative results trials aren’t perfect of course and we’ll talk in a moment about a big one that had some issues but we’re at a point where we need to either be vitamin D apologists saying forget
What those lying rcts tell you and buy this supplement it’s an $800 million a year industry by the way or conclude that vitamin D levels are a convenient marker of various lifestyle factors that do associate with better outcomes a marker of exercise of getting outside of eating a very
Diet or perhaps just perhaps Vitamin D supplements do actually have an effect it’s just that the beneficial effects are matched by the harmful stay Tuned the Women’s Health Initiative remains among the largest randomized Trials of vitamin D in calcium supplementation ever conducted and a major contributor to the negative outcomes of vitamin D trials but if you dig into the inclusion and exclusion criteria for this trial you’ll find that individuals were allowed to continue
Taking vitamins and supplements while they were in the trial regardless of their randomization status in fact the majority took supplements at Baseline and more took supplements over time that means of course that people in the placebo group who were getting sugar pills instead of vitamin D and calcium
May have been taking vitamin D and calcium on the side that would certainly bias the results of the trial towards the null which is what the primary analyses showed to it the original analysis of the Women’s Health Initiative trial showed no effect of randomization to vitamin D supplementation on improving cancer or
Cardiovascular outcomes but the Women’s Health Initiative trial started 30 years ago today with the benefit of Decades of followup we can reinvestigate and perhaps relitigate those findings courtesy of this study appearing in the annals of internal medicine Dr Cynthia Thompson of the Mel and Enid Zuckerman College of Public
Health at the University of Arizona and colleagues LED this updated analysis focused on two findings that had been hinted at but not statistically confirmed in other vitamin D studies a potential for the supplement to reduce the risk of Cancer and a potential for it to increase the risk of heart
Disease now the randomized trial itself only lasted 7 years what we are seeing in this analysis of is outcomes that happened at any time from randomization to the end of 2023 around 20 years after the randomization to supplementation stopped but the researchers would argue that’s probably okay cancer and heart disease take time
To develop we see lung cancer long after people stop smoking after all so a history of consistent vitamin D supplementation May indeed be protective or harmful okay you want some findings here’s the Topline results those randomized to vitamin D and calcium supplementation had a 7% reduction in
The rate of death from cancer that was driven primarily by a reduction in coloral cancer this was statistically significant also statistically significant those randomized to supplementation had a 6% increase in the rate of death from cardiovascular disease put those findings together and what do you get stone cold nothing in
Terms of overall mortality okay you say but what about all that supplement mation that was happening outside of the context of the trial biasing our results towards the null the researchers finally clue Us in first of all I’ll tell you that yes people who were supplementing outside of the trial had higher Baseline
Vitamin D levels a median of 54.5 versus 32.8 animals per liter this may be because they were supplementing with vitamin D but it could also be because people who take supplements tend to do other healthy things another correlation to add to the great Cathedral in order to get a better view
Of the real effects of randomization the authors restrict the analysis to just those who did not use outside supplements if Vitamin D supplements help these are the people they should help this group had about an 11% reduction in the incidence of cancer that was statistically significant and a
7% reduction in cancer mortality that did not quite meet the bar for statistical significance and there was no increase in cardiovascular disease among this group but this small effect on can caner was nowhere near enough to significantly reduce the rate of all cause mortality among those using supplements vitamin D supplementation didn’t really
Move the needle on any outcome I know what you’re thinking how many of these women were vitamin D deficient when we got started these results May simply be telling us that people who have normal vitamin D levels are fine to go without further additions nearly 34s of women who were
Not taking supplements ENT entered the trial with vitamin D levels below the 15 animals per liter cut off the author suggest would qualify for deficiency around half of those who use supplements were deficient and yet frustratingly I could not find data on the effect of randomization to supplementation
Stratified by Baseline vitamin D level I even reached out to Dr Thompson to ask about this she said quote we did not stratify on Baseline values because the numbers are too small statistically to test this sorry in the meantime I can tell you that for your average woman
Vitamin D supplementation likely has no effect on mortality it might modestly reduce the risk of certain cancers while increasing the risk of heart disease through coronary calcification probably so there might be some room for personalization here perhaps women with a strong family history of cancer or other risk factors would do better with
Supplements and those with a high risk of heart disease would do worse it seems like a strategy that could be tested in a clinical trial but maybe we ask the participants to give up their extracurricular supplement use before they enter it
