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On the article there is no mention of B12 supplementation and cancer risk. For example, there is evidence that high vitamin B12 supplement intake is associated with increased risk of lung cancer [1], [2], [3]. There is also evidence that folic acid combined with vitamin B12 supplementation is associated with an increased risk of colorectal cancer and prostate cancer [4], [5]. There is no association with gastric cancer [6] or pancreatic cancer [7]. I believe that the lung cancer association with high supplement use should be mentioned on the article. Leaving this here so I can hear from other users what they think about this. Psychologist Guy (talk) 21:06, 20 November 2022 (UTC)
Psychologist Guy Very interesting question, especially given the very high dose, non-prescription products available in the US and elsewhere, and a large amount of literature on lengthy clinical trials of B12 alone or in combination with other vitamins. I will see what else is in the lit. David notMD (talk) 12:10, 21 November 2022 (UTC)
Psychologist Guy Your 5 & 6 are the same ref (Fanidi et al, PMID 30499135), and your 7 is a review that cites only Fanidi. The study in question is not about supplement intake, but rather comparing high to low circulating B12. The two prostate reports were also not comparing supplemented versus not, but rather circulating high to low. When I looked at literature limited to meta-analyses and systematic reviews, I found Yang (2018 PMID=30430082) reporting no association of lung cancer with B12 status. The only review I found with large dose supplement in the design was Araghi (2019 PMID 30341095) which had a supplement group at 500 ug/day for B12 and 400 ug/day for folate, and reported an increased risk for colorectal cancer. Collectively, my opinin is that is no enough evidence strong enough to justify mention in the article. David notMD (talk) 03:54, 4 December 2022 (UTC)
Thanks for looking into this, I agree right now there is not enough evidence so its not worth including on the article. I think we need 10+ more years research on this. There is also a lack of trials on this topic currently as most of the studies in this area are observational, the only review of trials I found [8] reported no significant effects. Psychologist Guy (talk) 18:08, 7 December 2022 (UTC)
