[bd]

Hard to tell much about B vitamin supplement effects on non-smokers from this study.

Researchers themselves excluded never-smokers from more detailed stratified analysis because of their small number.

There were only 60 cases of lung cancer in never-smoker category (out of 36,381 people => 0.16%).

In comparison there were 748 cases of lung cancer in smoker categories (former + recent + current) (out of 40,737 people => 1.84%).

So there is 11.5x higher risk of lung cancer simply by smoking (including people who stopped smoking).

For comparison the highest hazard ratio from this study was 3.71x for a category of current smoker taking >55ug/d B12 vs current smoker who is non-user of B12.

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Also curiously, the worse risks seem to be associated with people who stopped taking vitamins than people who currently use vitamins (B6: 1.97x vs 1.38x, B9: 1.65x vs 1.05x, B12: 2.58x vs 1.19x - individual supplement use status former vs current).

Plus smaller doses of B6/B9/B12 shown in this study to pretty much universally lower lung cancer risk by a bit (hazard ratios of 0.8-0.9x ranges; one noticeable outlier >600ug/d B9 in recent smokers halving risk of cancer).

[jxy]

Some people hate statistics for a reason, and this is the exact reason. It is outrageous how the author conveniently manipulated the data to support the claim in their paper.

For those of you who want to do your own analysis, assuming their data are authentic, take a look at their Table I:

http://ascopubs.org/na101/home/literatum/publisher/asco/jour...

[bd]

Digging deeper into tables in the paper, I realized there is actually even less data about non-smokers than I thought.

Out of those 60 non-smokers with lung cancer apparently just 20 were men (out of 14,208 study participants who were men and non-smokers => 0.14%)

http://ascopubs.org/na101/home/literatum/publisher/asco/jour...

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Curiously this also means non-smoking women have 1.28x higher chance to get lung cancer than non-smoking men (unrelated to vitamins).

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For never-smokers vs smokers men risk ratios are then (again unrelated to vitamins):

- current smoker: 31.7x higher risk

- recent smoker (stopped < 10 years ago): 21.3x higher risk

- past smoker (stopped > 10 years ago): 8.9x higher risk

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Take home message: stop smoking!

Precautionary principle: if you take B vitamin supplements, you can continue (for slight decrease of cancer risk), just make sure you aren't taking mega-doses (especially if you still smoke), but really - stop smoking - the sooner you do less cumulative harm you get.

[Legogris]

I would also guess that smoker who experience health problems are more likely to start supplementing.