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While I always appreciate a critical view on supplements, I have to say that this is a really crappy paper that shouldn’t give you a bad feeling about or even keep you from taking B vitamin supplements - at least unless you are a smoker.
My take? Although the results are likely due to chance, and the way papers like this are promoted in the media really drives me mad, the associations, which are far from evidence, at least warrant some further investigations allowing for more definite conclusions. Until then, smokers (and only smokers!) may be well-advised not to take high dose B-vitamins, just in case. They are much better adviced, however, to quit smoking.
Your first point is incorrect. There was a link between b6 and b12 intake and lung cancer in male non-smokers
IRRC that link was not statistically significant - only when he looked and smokers and non-smokers together, it became significant.
Anyway, I have done some digging into the literature and finally found a study that clearly falsifies Brasky’s hypothesis:
A RCT in 12,064 mycordial infartion survivors, half of them taking 1 mg(!) of B12 daily (plus 2 mg of folic acid) for a mean follow-up of 6.7 years. No benefits for any of the primary endpoinds. BUT:
“By contrast, with more than 1300 incident cancers during up to 7 years of treatment with 2 mg folic acid and 1 mg vitamin B12 daily, SEARCH provides no evidence of adverse effects on cancer at any particular site including […] lung cancer in 116 (1.9%) vs 122 (2.0%) (RR, 0.95; 95% CI, 0.74-1.23)”.
Mind you, this is a RCT, the only kind of study that can actually establish a cause-effect relationship in humans. It was large and long-term. With a B12 dose 20 times as high as the dose range where Brasky’s data massage of an observatory study relying on self-reported(!) supplement intake found a sharply increased risk of lung cancer.
This is what bothers me about Brasky. Had he done his homework and was he an intellectual honest researcher, he would simply have published his results without fuss, cautiosly mentioning the conflicting and unconclusive evidence and encourging further research into a possible mechanistical between supplemental B12 and lung cancer to either validate or falsify his hypothesis - instead of going full-blown PR, passing correlation off as causation (to generate sensationalist media headlines) and - probably needlessly - scaring thousands people about the supplements they are taking.
Dr Brasky has a history of reporting negatively on supplement issues and can manipulate the media with his press releases. He does infer an increased risk on non smoking men but it is vaguely implied in the release. Furthermore, relied on “patient reports” (for ten years) and “statistical methods”…which allowed these conclusions, although many confounders. Later in the release it changes language in quotes from unqualified link to “may cause an increased risk…….” and also states that “doses are much higher than anyone would really take in ten years….” or something to that effect. This is crap. Furthermore, we don’t know of actual serum B12 in these individuals……does it matter ?…..I would think so. What about the relative risk of a lung cancer versus the known downstream problems with chronic B12 deficiency, such as in PA?
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