Pernicious Anaemia Society
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B12 - An "important nutrient for genetic stability, DNA repair, carcinogenesis, and cancer therapy"

I have a particular interest in this as a cancer survivor, recently re-staged to stage 4 breast cancer. I had severe b12 deficiency some years back, but my levels have been corrected and always show high on tests these days. I continue to receive regular injections (every 8 weeks).

I thought some of you might find the article below interesting as it explores the effect of B12 (or its absence) on cancer. I have copied out the part pertaining to b12.

"Protective Vitamins

Vitamin B-12

Vitamin B-12 has not been proven to be an anti-cancer agent, but there is some evidence indicating that it could be beneficial. The form of administered vitamin B-12 may be important.

Some experimental cancer studies have been carried out with various forms of vitamin B-12. Methylcobalamin inhibited tumor growth of SC-3 injected into mice [111], and caused SC-3 mouse mammary tumor cells to undergo apoptosis, even when stimulated to grow by the presence of growth-inducing androgen [112]. Methylcobalamin, but not cyanocobalamin, increased the survival time of mice bearing implanted leukemia tumor cells [113]. 5'-deoxyadenosylcobalamin and methylcobalamin, but not cyanocobalamin, were shown to be effective cytotoxic agents [114]. Methylcobalamin also was able to increase survival time and reduce tumor growth in laboratory mice [115].

Laboratory mechanistic evidence for the effects of vitamin B12 were seen in a laboratory study with vitamin B-12 deficient rats. Choi et al [116] found that the colonic DNA of the B-12 deficient rats had a 35% decrease in genomic methylation and a 105% increase in uracil incorporation, both changes that could increase risk of carcinogenesis. In two prospective studies (one in Washington Country, Maryland and the Nurses' Health Study) a relation between lower vitamin B12 status (but not deficiency) and statistically significant higher risk of breast cancer was found [117,118]. So, there is evidence from laboratory studies, prospective cohort studies, and mechanistic studies showing that vitamin B-12 is an important nutrient for genetic stability, DNA repair, carcinogenesis, and cancer therapy."

8 Replies

I think you maybe inadvertently gave evidence in your opening statement.

You say you had very severe b12 deficiency and had these levels corrected.

There is now a lot of evidence that these blood levels were not designed to reflect what is going on at cellular level.

If I can summarise quickly:

Doctors and scientists believed that the illness progressed like this:

Anaemia first, neurological and cellular damage follows

So, if the anaemia is prevented the neurological and cellular damage cannot occur.

The anaemia is treated very easily (it only takes 6 days for new reticulocytes to be made)

The problem is that the illness actually progresses like this:

Neurological damage producing anaemia. (The anaemia is an indication that the DNA synthesis is already going wrong)

So, reversing the anaemia is only resolving one aspect of the illness.

Because the anaemia aspect of the illness is quickly and easily treated it doesn't take much to reverse the blood levels of b12 to show the patient is treated - but only if you believe the anaemia is first in the illness progression - what it doesn't show you is how the illness is progressing or what damage has been caused at cellular level.

So, you can see from the information you provide, why b12 is important - it is an essential co-enzyme in some metabolic functions andn one in particular relating to DNA.

Your information is very much appreciated - particularly relating to the effectiveness or otherwise of cyanocobalamin in these experiments!

But I hope that you can see how much people rely on test levels when in fact these mean little or nothing and particularly after treatment commences.

B12 has always performed an essential function relating to DNA synthesis - and we are being undertreated because doctors think it's a blood condition first. It isn't.

As an aside I know that warped vitamins are used in treating some forms of cancer.

I hope the bit of information provided is fair exchange for the information you provided us as you have obviously got a keen interest in b12 and resulting illness!

1 like

That's very interesting, many thanks for your reply. I had no idea that it was the neurological damage that caused the anaemia.

I totally agree with you that treating the anaemia is only one aspect - and I'm sure many of us have had first hand experience of that.

Best wishes,


1 like

Hi mrstee,

I do remember you from previous forum, is this your story?


There is a lot of conflicting research, but as Pat says in the topic link below having good cells is what is needed to fight anything, see:


Kind regards,



There's not that much conflicting evidence, Marre - the new research proves that the anaemia is a direct effect of DNA synthesis going wrong ie the cells aren't replicating. It's the cell problem that causes anaemia.


Hello again, Marre,

Yes that's me. Lovely to hear from you again and I do hope you are keeping well.

Thanks for posting those links - there's quite a lot to read there - I will take some time and go through it.

Best wishes,



It seems there is an association with genotype, and possibly folate, other B vits (B6), but again it seems to me conflicting see:


.... and they used to think that PA was caused by folate deficiency...


But it is in a way. Here in the US is 23andme, and over the counter gene test for about 75 euros or so (99$US) which gives you the "big stuff" of your genetic info in raw data. You buy an online program called Promethease ($5US) and it processes the data and generates the reports. It then gives you a searchable data mining program called SNPedia which identifies Single Polymorohisms--SNPs, like the MTHFR variants which 'govern' so to speak how your body utilizes (or doesn't!!) B12 and folate/folic acid. For people with these variants folic acid is worthless! One third of people carry these MTHFR variants. If you have them, your numbers could be sky-high and all the cyanocobalamin in the world would still be useless.

It's what I found out. Search "MTHFR" online. It's a huge game changer. I'm just saying that when you start puzzling "how did this happen to me?" you're peeling the layers of a huge onion. You figure one thing out, then find there's another factor under that, then another layer of complexity, and another, and another.

I did a saliva gene test today that looks at mitochondrial disease which is really getting to (I hope) the end of my mess. I'm going in 3 weeks for a week at our National Institutes of Health in Maryland as a study subject!! Just me, not a group of patients, JUST ME. It took two MDs handing over 2 years of fruitless work and six meetings where I guess they went through my medical history wondering how I survived at all considering my genetics.

Just don't assume we are all the same! Because they think I'm just the tip of an iceberg! Wild, eh?

Keep digging!


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