I recently read a few articles which were based on medical studies which indicated that many years of high dose b12 increased the rate of people developing lung cancer. The articles I read were from the National Institutes of Health, Ohio State University Comprehensive Cancer Center and Harvard Health Publishing. These studies were based around subjests that had used high levels of vitamin b12 for numerous years, some as many as 10 years. There was a significant increased risk among men and even moreso among male smokers. There was very little to no increase among women. Thankfully I am not a smoker but I do have PA and use high dose cyanocobalamin, 1mg 2 times per week for 1 year, hence my concern. I am curious if others here have imformation regarding this topic. Thanks for any responses and I will post links to the articles.
I am not a medically trained person jimmel196 but I have been having cyanocobamalin injections for pernicious anaemia for nearly 49 years and I'm still very much "clivealive" coming up to the age of 80.
Do you really need to inject that frequently?
Meanwhile I hope that you will be able to open the link below
I'm sorry to be so late giving a more detailed response to you. My doctor felt that I should stay on 1mg cyanocobalamin two times per week for a maximum of two years unless my widespread neuropathy (semi-numbness in feet, legs and up to my waist and hands and arms up to my elbows) improves. I also had a MRI on my complete spine this past November which showed subacute combined degeneration of my cervical spine. My doctor new of a Mayo Clinic study where pernicious anemia and/or b12 deficiency patients with serious neurological symptoms were treated with hydrocobalamin 1mg twice weekly for two years or until symptoms improved. In the US cyanocobalamin is the more frequently used form of b12. I guess I could have shortened it but that is why the amount and frequency of b12. I read many posts regarding pernicious anemia and have read many of yours dating some years back. Thank you and all the others for the helpful information for which you all provide. I retired from being a paramedic for 32 years and have learned much more about b12 deficiency and pernicious anemia on this forum than I ever knew prior to being diagnosed a year ago.
I’ve heard about these articles but don’t have time right now to read in detail. I have read the opposite previously: that B12 deficiency can CASUSE can cause cancer with the comped DNA replication processes dependent on B12. There’s little research into this however. Anecdotally, I’ve noticed a possibly connection between B12 deficiency causing cancer.
Here are some questions as I’ve only briefly glanced at this article:
1. The people who supplemented with B12, was that because they were diagnosed with B12 deficiency and were given tablet form? Does it state whether they were given injections or tablet form? If tablet form it’s unlikely to have made a difference with B12 def patients yet they’d have had falsely elevated B12 blood results. Their cancer could have been a result of (properly) untreated B12 deficiency.
2. 55mcg of B12 a day l. Is that a daily average? If they took it every 3 months, for example, it may not have been sufficient to prevent the B12 deficiency progressing.
3. 25 % of B12 deficiency patients have High b12 in blood serum. These patients lack transcobalamin so B12 cannot be pulled from blood to be used by body. Were these patients tested for this? Their cancer could have been a result of this untreated B12 deficiency.
I hope that these articles don’t stop people taking regular B12!
"If tablet form it’s unlikely to have made a difference with B12 def patients yet they’d have had falsely elevated B12 blood results."
There is no such thing as 'falsely elevated B12 levels'.
Your body has no idea how B12 in the blood got there. B12 from injections is treated exactly the same as B12 from oral supplements, is treated exactly the same as B12 from food. Once it's in the bloodstream it make no difference.
If people have high levels of B12 from oral supplements it's because they can absorb oral B12. For people with a B12 deficiency caused by a lack of B12 in the diet, or because of inefficient absorption tablets can make a difference.
Yes, poor choice of words - I have some cognitive decline (my brain ain’t wot it use to be!), was rushed and with a talkative child next or me... I felt compelled to reply quickly to the original poster because I know 2 people who have stopped their B12 injections because of this research....this has been circulated on a few online forums and one of the people who has stopped was informed about this research by his dr.
So when I wrote “falsely elevated” level, and I’m sure you will correct me if I am wrong, is that the level of B12 in the blood could represent the useless, non activated form of B12 as opposed to that which has been activated and useful. So, an assumption that active B12 was falsely represented by the B12 level. Does it say which B12 test was carried out?
I hope that others don’t follow suit and stop injecting based on this and that other drs don’t refer to it...I hope that there can be some more meaningful discussion on this research before conclusions can be made
"So, an assumption that active B12 was falsely represented by the B12 level. Does it say which B12 test was carried out?"
It doesn't matter whether the test was for Active B12 or not.
If you want to count the number of sheep in a flock you can count the number of heads, or you can count the number of feet and divide by four. You're going to get roughly the same answer.
The only way the type of test could matter would be if somebody had a problem with the transport protein transcobalamin. There are genetic conditions that cause such a problem. But they are severe and they make themselves apparent in childhood.
Even then the route that the B12 got into the blood wouldn't matter.
It's been a while since I've logged on here, but if you recall my previous comments, I'm someone who had normal B12 and MMA levels after taking B12 sublinguals (indicating that they were "in my system"), but still had significant neurological problems that were only reversed by taking B12 injections.
In my case the blood tests were misleading, which is why it took me over 15 years to try shots. I did not have any problems in childhood, and my genome does not show any significant mutations in transcobalamin production genes.
I can't be the only one. Discouraging people from trying shots is exactly the kind of advice that kept me sick for well over a decade. I encourage everyone to try a B12 shot before making up their mind. I knew immediately.
For goodness sake how do some people become doctors & how do these studies get published with a such a big confirmation bias? what was the context your friends doctor informed this about this research (does he smoke?) as this is a clear example of why correlation does not necessarily imply causation as i can see many issues with this study for the start the title on the harvard article "B vitamins may raise risk of lung cancer in men who smoke" when it at most referring to 3 of the B vitamins is careless.
We don't know what form of vitamin B12 was being taken but I suspect its was cyanocobalamin at least in the United States which has to be converted to hydroxocobalamin and I believe this requires glutathione (which might be in short supply in smokers ncbi.nlm.nih.gov/pmc/articl... to remove the cyanide molecule. Then we already know smokers already have issues with cyanide metabolism (Tobacco amblyopia) which is why at least the UK switched from cyanocobalamin to hydroxocobalamin injections in the 1980s. europepmc.org/backend/ptpmc...
Also where is the control for the smokers who only had high dose vitamin B12 as I doubt it would be hard to find a few smokers with pernicious anemia who didn't take any other supplements.
In the same way that a body cannot differentiate between injected/tablet/food B12 in the bloodstream, why would a male/female body react differently to same ?Significant increase in lung cancer rates in men and very little/no increase in women seems an unlikely result.
I have a question, fbirder about that. I had been exhausted for years-diagnosis of chronic fatigue syndrome and when I was not taking oral B12, my B12 level was below normal. No one tested me for PA. I began taking oral B12 for years B12 labs were greater than 2000 and my mean corpuscular volume was 102. Since reading that a high MCV is a classic sign of low B12 or PA. I insisted on injections and my life changed dramatically.
I have found that I can only go four to five days between injections or symptoms return.
Also, I don’t consider1mg cyanocobalamin “high dosage”? I think that’s the average ampoule size.I speak to many people who inject that or more daily...it’s helpful to share that article and so it can be discussed
We know from reading posts on this forum that many Pernicious Anaemia patients suffer from it for many many years before they get a diagnosis and CORRECT treatment . Whilst struggling with low B12, their immune systems are very much compromised , and as a result , they can get many illnesses including cancer . If this cancer is discovered after treatment with b12 injections , when they will have very high levels of B12, then some doctors might assume that those high levels cause cancer . But here we know that high levels are very safe ( Stichting report ) , indeed necessary for P.A. patients . Keep on injecting to keep well ! Best wishes .
I also read an article which was a Norwegian study linking high B12 usage with lung cancer. It seems that more investigations need to be carried out into this.
I hope everyone understands that my intent is to not incite fear but to gather information from people on this forum who know much more about b12 deficiency and treatment than I do. It is well publicized material from reputable sources but I could not understand how one could be linked to the other. It's not going to make me not use b12 because pernicious anemia cause a lot of problems for me including weakness, episodes of double vision, widespread neuropathy as a result of subacute combined degeneration of my spinal cord, and the list goes on. I have no choice but to continue my b12. Sorry to anyone if this came across wrongly but I was curious for others input. Thank you.
Discussion is vital. Fear of going backward makes more sense than fear of moving forward - but both can feel restrictive after a while, and sometimes hard to tell the difference.
I feel as jimmel196 does, that currently at least, there is no choice for me.
I kept going to one consultant after another, just in case. Nothing more "serious" found, no way of controlling symptoms other than frequent injections.... B12 high now but MMA, folate, ferritin and vitamin D all finally under control. DNA did not reveal any reason to explain why I need more B12 injections than the "norm", why MMA remained raised for so long.
Far more research is needed into all of this.
Why some need more B12 than others - this is what the PAS are looking into. Ignoring this fact, or dismissing it as addiction, or a panacea for a hypochondriac is insulting to the many patients who have tried hard to fit a pattern and failed, and to the GPs who have seen for themselves an otherwise inexplicable improvement.
B12 injections have been in use for many years now.
If, when used in Pernicious Anaemia patients, the high B12 levels claimed resulted in greater risk of lung cancer, we might expect to see a higher rate of lung cancer than in the general population.
We don't. We see a lower rate. At least according to this paper:
Lahner E, Capasso M, Carabotti M, Annibale B. Incidence of cancer (other than gastric cancer) in pernicious anaemia: A systematic review with meta-analysis. Dig Liver Dis. 2018 Aug;50(8):780-786. doi: 10.1016/j.dld.2018.05.012. Epub 2018 May 24. PMID: 29887343.
PA patients had a lower RR of colorectal, breast, liver, oesophageal, lung, thyroid, ovary, non-melanoma skin and kidney cancers but had a higher RR of biliary tract cancer (1.81:1.21-2.70), multiple myeloma (2.83:1.76-4.55), Hodgkin's lymphoma (3.0:1.35-6.68), non-Hodgkin's lymphoma (2.08: 1.58-2.75), and leukaemia (1.56:1.16-2.12).
f order, I am now confused. I have PA. The levels of B12 in my blood as measured by the usual bloodwork never caused alarm. However, the bottoms of my feet went numb, I was having confusion (e.g. On one occasion, I did not recognize where I was on my usual route home), and the constant presence of pins and needles in my limbs, plus the awful fatigue, no matter what remedies were tried. I was diagnosed by accident as the result of in depth bloodwork ordered by a hematologist because of problematic platelet count. It revealed the problem with intrinsic factor.
So...why was the B12 in my blood not doing it's job? My understanding was that it was not properly attaching itself to the red blood cells. I also believed that the usual type of lab test for B12 was not very accurate. Are you saying these two premises are incorrect?
I'm probably not the best person to give opinions to your questions but I am curious as to the frequency of your b12 injections and your latest b12 level, if you were told what it was. I am in the US as well, werd are you located?
Hi, jimmel196. I am in Minnesota. I was prescribed injections every two weeks by a neurologist not long after I was diagnosed. I self inject, even though it means paying for the cyanacobalamin and needles out of pocket because it saves having to get myself to the clinic when my energy isn’t good. It’s been a few years since my B12 levels have been checked, but I was always told they were in the normal range ...before and after treatment. That’s why I am confused. I thought I understood Martin Hooper’s explanation about the test and what it means in the blood stream from his books. But maybe I did not.
I'm in North Carolina, a little warmer here. I believe the articles were referring more to very high levels in the blood but regardless with my PA i I have no option with regards to b12 use if I want to maintain my health.
I'm in the US as well. I believe your understanding of the standard B12 test used in the US is correct. Martyn Cooper explained in his book, and also on the PA Society website, that there are problems with the machines used for the usual B12 blood test, and for me this helped me understand why for years my doctors thought my B12 was fine. It was within the lower-normal range even though there were symptoms typical of PA. MCV was also high. After PA diagnosis and treatment I saw a huge difference in my energy and clarity. Now I have to SI with methylcobalamin every 3 days to keep symptoms in check, but am much better than before. So yes, I believe the test used in the US isn't very reliable (I've heard the "active" B12 test could be useful, but haven't seen it in the US yet), and there is also the possibility that the B12 doesn't get used by the cells the way it should, though that science part is unclear to me. Hope this helps.
Thank you for responding. I had the same experience with getting diagnosed...all tests looked fine until a hematologist did in depth blood work for another issue. Interesting that you use methylcobalamin a in and the frequency you SI. Prescribed or from another source? I found a source for cyanocolblamin and am just starting to SI weekly. Noticing an improvement in fatigue, balance, and clarity of thinking.
A hematologist diagnosed me as well, after I insisted to my family doctor that I wanted to see a specialist due to continuing symptoms of extreme fatigue. Also I knew I have a family history of PA. All the family doctors I've seen didn't think there was anything wrong with my blood results other than a little out of range anemia-type levels (high MCV also). The hematologist taught me to SI, but was reluctant to increase my dosage to more than 1ml once a month of 1mg/ml cyanocobalamin for my SI. I saw a naturopathic physician who prescribed more frequent SI from vials that have a higher concentration (5mg/ml) because my symptoms were so bad. She suggested I try methylcobalamin from a compounding pharmacy, because she noticed some possible methylation issues in my genetics. We may in the future try other types of B12 to see which combo or type work best for me. Due to the frequent SI I didn't want to have too much cyano in my system; I know it's a small amount of cyanide, and cyanocobalamin is more stable, but methyl has worked well for me so far. Hope this helps!
So many personal stories on this website are similar, aren’t they? I have a family history of PA, too. Kept bringing it up with doctors to no avail. My mother would say, “I just know it is PA you have. Are you sure they understood that your mother has it?” Your reply does help. I will look outside the usual medical community if help is needed in the future. Thanks!
Yes, many of us sadly have had to try to convince our doctors to look more closely at what may be happening. I'm grateful this forum exists so we can cheer each other on and share helpful ideas.
The articles refer to 'increasing risk of' - which isn't really that useful a statement. Crossing the road increases your risk of being knocked down by a car but the causal processes are much more complex than that.One article included the following
B vitamins help strengthen the immune system, according to the researchers, so it is not clear why high levels of supplemental B vitamins would increase rather than decrease smokers' lung cancer risk. They speculated that the B vitamins might feed small, undetected tumors and make them grow faster.
Which is to say that the B vitamins may not be the cause of the cancer but might cause it to manifest more quickly - it is known that high levels of B12 will result in tumours growing quicker and larger than might otherwise have been the case.
I have great difficulty with terms such as "strengthen the immune system".
Always have found it difficult to accept in the context of auto-immune disorders. Where weakening the immune system might be thought to hold out hope of recovery! And, within the Covid-19 context, we have heard all too much about cytokine storms. Which suggests that an over-strong immune system can be lethal.
We need to be more considered and subtle than just to speak of strengthening (or weakening) of the immune system.
(I do appreciate that phrasing was within a quote which generally makes sense.)
22 years ago I was diagnosed with PA. At that point I could barely get out of bed. As soon as I began injections I learned that I needed an injection daily or my symptoms would be severe. Fortunately I had a Doctor that listened to me. So for about 12 years I injected myself daily with 1000 mcgs. B12. Then my doctor seemed to panic because a B12 test came back with 1500 in bloodstream and he refused to prescribe any injections at all. I decided to try sublinqual and told my doctor that and he agreed but said to try 5000 mcgs a day with the sublingqual which I did do. So for about 10 more years I used 5000 mcgs of sublingqual daily. I guess you can call that high dosage and I guess for 22 years can be considered a long time. As far as I know I don't have lung cancer. I know that's not a clinical trial but there you have it....one person's experience.
Thanks for sharing that information. You are quite the clinical trial and as I've said in a previous response, I have no choice but to inject more frequently than some medical wisdom suggests due to my neurological symptoms.
My doctor prescribed it and he used a local pharmacy that delivered it monthly. It came in a multiple dose vial. 30ml. I used 1000mcg's daily. The company's name was AMERICAN REGENT, INC. Shirley, NY 11967. I have kept an old used bottle just in case I needed the information one day. It came in handy today.
Well, this scares the crap out of me. I have been injecting cyanocobalamin daily for over a year (and less frequently before that) because I'm in the US and don't easily have access to other forms. If I don't inject daily, my neuro symptoms aren't bearable. I smoked for 10 years.
I was already worried about cancer due to my B12 being so low for so long. Makes me really sad to think about how long I was dismissed and misdiagnosed and the lengths I have had to go to to mitigate the resulting symptomatology -- and now to think that it might be poisoning me. Ugh.
I'm not entirely sure if they specified which form of b12. I believe the study was generally referring to people with very high serum b12 levels as a result of high dose b12 use.
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Received email and concerned about their statement re Vitamin B9 and B12
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Some might find this of interest - Dr Axe ?
B12 and cancer
B12 absorption issues stemming from poor sleep quality and deficiencies with Vitamin D and other b vitamins. 
