In an issue of the Journal of Clinical Oncology, published this week, researchers reported that taking vitamin B6 and B12 supplements in high doses (like those sold in many stores) appears to triple or almost quadruple some people’s risk of lung cancer.
cont/d... in theatlantic.com/health/arch...
Edit: To emphasise - the study found the correlation in male smokers only.
fbirder has replied further down the thread with another study which says why you shouldn't worry about this study.
Ummm that's very concerning. It feels as if this puts you between a rock and a hard place. If you only feel well by taking a supplement but that supplement might increase your chances of getting cancer. I wonder what the risk is of people taking b vitamins who are actually deficient?
It looks like a longitudinal study and appears to be showing correlation rather than causation. Similar studies previously that have seemed to indicate a link have sometimes been found later to be incorrect such as the idea that cholesterol in food cause cholesterol to build up in the body. This is now known Just not to be the case. So such studies warrant further research but should be viewed with the understanding that correlation does not equal causation
It would be interesting to know for example if the people on the vitamin group were taking vitamins because they ate a poor diet or because they already had health issues which they were hoping the vitamin might help with it maybe other factors about the group that caused the increased cancer rates.
Having said this, it is still worrying for those of us who need to take supplements because of absorption issues. Not sure what the answer to that is though other than to try to have healthy lifestyle in other ways to try to mitigate the overall risk?
Hmm scary, but let's remember the quantities in the study:-
"The research team is quick to note that the doses of B vitamins in question are enormous. The U.S. Recommended Dietary Allowance for B6 is 1.7 milligrams per day, and for B12 it’s 2.4 micrograms. The high-risk group in the study was taking around 20 times these amounts."
I'm an ex smoker but hubby is still puffing away and since we've discovered my B12 deficiency and seen the effects of that, he's taking a regular B Complex vitamin, I won't tell him to stop. So far one study shows increased mortality for men who smoke AND take over 20mg of B vitamins a day for years. I don't think many (if any) men fit that scenario in real life.
But giving up the smokes is always encouraged! 
I don't think the quantities are that high for a b12 supplement. In Thornes B complex there is 300mcg of b12. 20 x 2.4 mcg is only 48mcg. I take a b12 supplement of 1000mcg because of absorption issues which seems to be keeping my b12 around the 500 mark.
B6 is another matter and that is known to have toxic effects in high quantities anyway and it the NHS recommend that you shouldn't really take more than 10mg a day (unless advised to by a doctor) so 20mg over a long period is too much I would argue.
I was a 20 a day smoker in the 1970s and 1980s and all the while on cyanocobamalin B12 injections for P.A. and nobody told me.....! Plus for more than fifty years I have taken a "handful" of Brewers Yeast tablets every day
I did have "lung problems" diagnosed some ten years ago but that was due to exposure to asbestos dust in the 1950s when I was a lad helping a neighbour build a garage and during the 1960s when I was an electrician but there was no trace of cancer.
I'm still "clivealive" - somehow....
Good to show us all articles for and against supplementation of vitamins and minerals. Also who is behind the article, who writes it and also who sponsored the research.
I would treat this research with great caution until I knew with precision the funding arrangements of the study and the outcomes from a statistical zero baseline - not from a relative baseline. The pharmaceutical industry - particularly in the USA has for some time been trying to shut down access to over-the-counter vitamins and minerals. The only reason that I can see is that it will increase the quantum of sickness and therefore enhance profits.
Before anyone shouts "But that would not affect the outcome of research", please read Dr Ben Goldacre's book "Bad Pharma". Funding DOES affect research outcomes. Researchers do NOT bite the hand that feeds them.
Study results that say what Big Pharma want are quoted ad nauseum and the researchers are funded for further studies. Studies that contradict the Big Pharma narrative, have difficulty getting published and no further research cash from the pharmaceutical companies is forth coming. I think that they are trying to frighten B12 users with the (probably mythical) cancer bogey man. This "study" fails the bad-smell test.
'Lies, damned lies and statistics'.. Somethings never change?.
Exactly Capricorn!! The favourite tricks are to test a therapeutic effect that they are trying to discredit with too little of the therapeutic agent to produce an effect - or too much so that it has side effects. Other tricks are to choose a cohort (bunch of people for the study) that is unrepresentative of the general population or to set a meaningless reference range against which to test efficacy.
In one very famous study by a guy called Ancel Keys (now dead) in the 1950's a study that was initially called the "Twenty One Countries Study" looked at the impact of diet on heart disease. Keys wanted to prove that it was saturated fat consumption that caused it. His results did not substantiate his hypothesis in 14 of the 21 countries in which data was gathered. He fixed this by discarding the results from these 14 countries and re-named the study the "Seven Countries Study". He missed the fact that the prime suspect for heart disease was - and is - refined carbohydrate consumption, particularly sugar. This would be funny of it were not for the fact that 40 years of bad official dietary advice was based on this study. If you doubt this - check out the progression of the American waste-line and diabetes over this period.
So here is another mechanism that can rig scientific study results. Choosing which data can contribute to the final outcome. Lastly there is the statistical interpretation of the data and the conclusions drawn. These do not always accord with the raw data, but almost always accord with the commercial interest of the study funder.
The pharmaceutical industry does NOT want cures or unpatentable preventives (like vitamins). They want treatments that last a lifetime that can be patented. This provides a revenue stream for many years. A cure or prevention does not. I am afraid that we live in a rotten world.
There are lots of articles which say rubbish about Ancel Keys and his research. He choose the seven countries as they had the best data and had no obvious problem such as were Nazi occupied and therefore a large shift of diet was likely.
If all 21 countries are included the association between fat and heart disease mortality persists. It is silly to lay one of the key facts of a whole discipline(nutrition and health) on a single scientist from research decades ago.
The study relies on 'recall'. Not too scientific in my books.
Before everyone starts to get really worried about being treated with high dose B12 for B12 absorption problems please note that the actual study is reporting a correlation rather than a causal link.
I can't really comment on B6 as a cancer risk but high dose supplementation with B6 is inadvisable anyway for other reasons
Supplementation with B12/treatment with B12 has long been known to correlate to higher rates of cancers. There are a number of possible causal mechanisms but I'm not aware of any studies that have actually identified which are really at play. Some absorption problems - such as PA - are associated with higher risks of some times of cancer anyway. Being B12 deficient affects cell replication and so is a higher risk of cancer - so possible that what is being seen is the result of a period of B12 deficiency prior to treatment. Treatment with B12 after a mutation that leads to cancer has developped will also mean that the mutated cells replicate and tends to lead to larger tumours.
To try to explain the difference between a correlation and a causal link:
tall people tend to have bigger feet - but that doesn't mean that having bigger feet will make you taller.
Nevertheless I would prefer to take B12 treatment. I do not believe it causes cancer and , since cancer attacks the cells, it will have cell appetites.
An expert comments on this study, and why you shouldn't worry about it.
theconversation.com/vitamin...
I found a similar type of article too.
medium.com/@drrosswalker/vi...
His take is don't smoke!
I wish it were that easy.
I feel deeply for all those addicted to nicotine. I was a smoker for 38 years. I tried to give up many times, but it was just too hard. By my early 50s I had a terrible morning cough that I was sure was an indication of my inevitable fate.
Then, one Christmas I was struck down with a terrible dose of flu. For three days just the thought of smoking a cigarette made my lungs spasm.
After the first day I found that a couple of puffs on an e-cigarette kept the nicotine pangs at bay. So I stuck with that. Three weeks later I was smoking the e-cig with no battery. Two weeks later I was off the weed completely.
I am convinced that dose of flu saved my life. I really was convinced that my addiction was going to be the death of me, and that there was nothing I could do about it.
That's why I have great sympathy for smokers and why I'm so against nonsensical restrictions on e-cigs (or anything else that helps people to quit).
Oh I agree. The only way I got off cigarettes is by substitution via vaping.
Though one reason I use nicotine is for the mental boost, I've found it difficult to concentrate for years. I hope that once my nervous system has normalised with taking B12 I will be able to kick all nicotine...
Probably wishful thinking.
It is only people taking excessive amounts I think so normal amount should be fine.
Despite the many caveats I think the message is that one shouldn't take supplemental vitamins, especially in high doses, unless you really need to. You'd really need to separate out the participants in the study according to whether they were actually deficient in the first place, I would have thought? The figure quoted for B12 is much lower than the amount many of us are injesting though, worryingly 😬.
OK, I'm not a medical doctor but I am a biologist and I'm not worried yet. However, I will certainly be keeping an eye on future research and I'll see if I can find the original paper and raw data to take a closer look.
For any vitamin to have an effect, negative or positive, it needs to be absorbed by the body. The study doesn't mention anyone with PA being included in their trial so I assume they only included those without vitamin-related illnesses to reduce variables. As we can't absorb B12 in the usual way, it may be that the study doesn't apply to us. I would very much like to see a similar study which includes people with PA.
It appears to be a very well-done piece of research and I'm certainly not dismissing it - that would be very stupid. However, I think more work definitely needs to be done in this area.
I thought B12 was non toxic and that any excess was excreted in urine? So even without having PA I don't see how even large amounts could be harmful, or am I missing something?
Since it's incredibly hard to get a correct diagnosis of PA, and many of us are treating or being treated based on symptoms and an inaccurate blood test, rather than other accurate clinical evidence, it's important to know if these findings have any relevance. Not only is it difficult/impossible to get a medical diagnosis of B12 deficiency, it's also almost impossible to ascertain the cause - auto immune PA, genetic condition, gastric atrophy, stomach infection, temporary or ongoing dietary insufficiency, thyroid disorder? - and more.
Can oral B12 supplements help in a functional B12 deficiency and more q's 
Would high dose of oral b12 cause other problems?
Gp agreed to levo dose increase -and talked about B12 injections!
Vitamin B12: Side Effects and Cautions in Relation to Pre-Existing Health Conditions. 
MTHFR - high homocysteine and b12 in blood
