Smokers and Cyanocobalamin

by Jack Norris, RD • Last updated September 2017

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.

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