If you're a smoker, you might want to be aware of this (and stop smoking!). The following link is to a summary of a large scale study that examined long term high dose of B6 and B12. It's an observational study. By nature, the study can't conclude that long term high dose of B6 and B12 promotes lung cancer. However, it certainly suggests that male smokers have a significantly greater chance of getting lung cancer if they supplement with higher B6 and B12 long term. The study does NOT conclude that non smoker males have a higher risk of cancer.

The main point of my post is that - if you smoke - and supplement with extra B6 and B12, observational study indicates you're at increased risk of getting lung cancer. I imagine most people here don't, but if you do, then here's another reason to quit.

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