B12 and Lung Cancer

A recently-released study from the University of Washington found an increase in lung cancer among male smokers with a vitamin B12 intake of 55 µg per day or more (3). There was no increase in lung cancer among women, women smokers, or non-smoking men.

Because this study raises concern about vitamin B12 supplements for smokers, I’ve updated the VeganHealth.org article, Smokers and Cyanocobalamin. The article is short, so I’ve reproduced it here:

Because smokers receive cyanide from smoking, and vitamin B12 can actually be used to detoxify cyanide due to its strong affinity for the cyanide molecule, there’s a concern that perhaps cyanocobalamin will not be effective for smokers.

For example, hydroxocobalamin injections decreased blood cyanide levels by 59% in smokers (1.5-3 packs/day) and cyanide was eliminated in the urine as cyanocobalamin (1). In another study, smokers were found to excrete 35% more B12 than nonsmokers (2). But in another, serum B12 of smokers didn’t differ from nonsmokers, and the Institute of Medicine concluded that “The effect of smoking on the B12 requirement thus appears to be negligible (2).”

But most smokers have an intake of hydroxocobalamin, and other non-cyanocobalamin forms of B12, through animal foods, while vegan smokers do not have a non-cyanocobalamin source of B12 unless they seek out a supplement. There’s no research on B12 and vegan smokers, but I’m not aware of any who have had trouble warding off B12 deficiency.

Additionally, one prospective study found an increase in lung cancer with B12 supplements among male smokers for the highest intake group of 55–275 µg/day (3). Other research has not found an association with vitamin B12 in cancer, but it hasn’t been studied thoroughly among male smokers. However, an arguably better piece of evidence comes from a randomized, clinical trial that did not find an increase in cancer with increasing serum B12 levels (from 400 µg/day) in a population with a high rate of smoking (4).

At this time, there doesn’t seem to be enough evidence to warrant separate vitamin B12 recommendations for smokers.


1. Forsyth JC, Mueller PD, Becker CE, Osterloh J, Benowitz NL, Rumack BH, Hall AH. Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers. J Toxicol Clin Toxicol. 1993;31(2):277-94.

2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 2000.

3. Brasky TM, White E, Chen CL. Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol. 2017 Aug 22:JCO2017727735.

4. Ebbing M, Bønaa KH, Nygård O, Arnesen E, Ueland PM, Nordrehaug JE, Rasmussen K, Njølstad I, Refsum H, Nilsen DW, Tverdal A, Meyer K, Vollset SE. Cancer incidence and mortality after treatment with folic acid and vitamin B12. JAMA. 2009 Nov 18;302(19):2119-26.

2 Responses to “B12 and Lung Cancer”

  1. Daisy Says:

    Jack, I’m appalled at your response. This study finds a solid foundation between high doses of B12 and 6 and lung cancer and not just among smokers. Almost all B12 supplements are mega doses.

    From the link: “In contrast, use of vitamin B6 and B12 from individual supplement sources, but not from multivitamins, was associated with a 30% to 40% increase in lung cancer risk among men. When the 10-year average supplement dose was evaluated, there was an almost two-fold increase in lung cancer risk among men in the highest categories of vitamin B6 (> 20 mg/d; hazard ratio, 1.82; 95% CI, 1.25 to 2.65) and B12 (> 55µg/d; hazard ratio, 1.98; 95% CI, 1.32 to 2.97) compared with nonusers.”


  2. Jack Norris RD Says:


    I read the article and corresponded with the author who wrote this to me:

    “Please note that the increased risk that we observed was more or less restricted to male current smokers. Thus, there is little cause for concern among men but rather men who smoke and who are taking high doses of B6/B12 (and that this risk is several times that of men who smoke who do not take high doses of B6/B12).”

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