Hi, Jeff,
Got a question today that is making my head hurt a bit... it looks like safe B12 supplementation is even more complex...
(I've searched the forum using the tools and no answers returned for B12 - so I apologize if this is already answered, couldn't find it.)
I was reviewing Dr. Tom Campbell's article on B12 when I saw his 2018 update:
https://nutritionstudies.org/12-questio ... tamin-b12/"Update on 5/10/18: ... Recently, there has been some evidence that large dose B12 supplementation may be associated with an increase in cancer risk in some groups. *Because of these findings, and because I can’t find plain B12 supplements smaller than 500 mcg per pill, I’ve been recommending people take a multivitamin."
Dr. Tom references this study: Brasky, T. M., et al. (2017). “Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort.” J Clin Oncol: JCO2017727735.
See it at:
https://ascopubs.org/doi/full/10.1200/JCO.2017.72.7735Apparently the implications of high daily B12 supplementation are an increased risk of up to nearly 2x for lung cancer assuming high blood levels of B12. As far as I could make out the proposed causative mechanism, it appears related to interference with the DNA proof reading mechanism through involvement with methionine and homocysteine interactions. The study was arranged such that those taking a daily multivitamin would be in the lowest quartile, thus they were not found to be at risk.
Accordingly Dr. Tom recommended a multivitamin. This flies in the face of Dr. McDougall and T. Colin Campbell's recommendations to avoid multivitamins and other such sources of single concentrated nutrients.
Dad says - "Avoid synthetic isolated nutrients like vitamin pills" - son says "take a multivitamin"..... Oy, vey...
I'm not in a hurry to consume a multivitamin to get B12 - given the fact that most are loaded with isolated vitamins A and E, as well as synthetic folic acid - all implicated in studies of cancer and condemned by Campbell, Dr. McD, and others, in that order...
The 2017 study in itself has issues - would be nice if they tried this on a WFPB population, why such different results in different parts of the world, would be nice to boldly separate B6, 9 and 12 effects, and so forth.
Anyway, finally on to the questions:
I was under the impression that there was a severe limit to the amount of bioavailable B12 due to a limited supply of intrinsic factor. Thus my understanding was if one consumed 5000ug of B12, perhaps 15-25ug might make it to the bloodstream. Being water soluble to boot, any B12 that isn't stored shortly gets removed by the kidneys, no? (Otherwise, one 5000ug every few years would do it...)
Thus - with so little B12 making it to the target, how do the people in the studies sustain such a chronic high B12 level in the bloodstream for 10 years? Is this a study of a bunch of people trying to kill themselves by simultaneous dietary and supplemental B12 overdose? Does this only apply to people with an already maximum amount of stored B12? Disease of excess, B12...?
Would appreciate insight here - to say the least.
Finally - it doesn't follow in my mind that if the high dose B12 on the market is problematic we should therefore eat a vitamin pill every day for the rest of our lives just to get in 10-20ug of B12 - that after all might or might not be there - no oversight on these pills. It's relatively easy to get a 100ug B12 and either cut it in 4 parts or take one twice a week - IF that means it supplies the needed 2.5ig usable B12... does it?? Or how much is enough???
We're told the larger doses can be absorbed to a certain extent even in the absence of a healthy amount of intrinsic factor.
We're told that getting 15-25ug into the bloodstream is par for the course for 2500-5000ug taken orally.
If we need 2.5ug a day, that seems to demand popping 5000ug about once a week to be safe? (15/2.5=6)
What's the right way to do this?