This is the title of an article published recently (September 2019) in which over 5,000 patients with lung cancer were compared to a similar number of age-matched control subjects who did not have lung cancer. These two groups qualified if their medical records contained 'pre-diagnosis' vitamin B12 levels (in the case of the lung cancer group) to see if higher B12 levels were, as other studies have shown, associated with higher risk of cancer. The results confirm that among subjects who received vitamin B12 supplements, and whose blood levels were higher, did have a statistically significant higher risk for developing lung cancer. And here is the scary part, the blood levels measured would fall in the normal range as reported by most laboratories (118 - 701 pmol/L). In this study, vitamin B12 levels above 338 pmol/L (in the lower third of the normal range) were already associated with a higher cancer risk, which increases with increasing B12 levels. This serves to reinforce that the body needs just the right amount of B12 (RDA is 2.4 microgram/day) and extreme doses of 500 - 5,000 micrograms found in many supplements, is way too high.