Research from a large study does suggest that taking high doses of vitamins B6 and B12 for many years is linked to an increased risk of lung cancer in men, particularly smokers. Researchers analyzed data from 77,118 adults participating in the Vitamins And Lifestyle (VITAL) study designed to evaluate vitamin and mineral supplements in relation to cancer risk. When they joined the study, the participants were between the ages of 50 and 76. They were asked about their use of B vitamin supplements over the previous 10 years. During the six years after enrollment, 808 of the men developed lung cancer.
The study was the first to look at the effects of long-term, high-dose use of vitamins B6 and B12 and lung cancer risk. The researchers said that these doses had been long touted by the vitamin industry for increasing energy and improving metabolism. They noted that the supplements had been thought to lower cancer risk.
After adjusting for a number of cancer risk factors including smoking history, age, alcohol consumption, personal history of cancer or chronic lung disease or a family history of lung cancer, the researchers found that the long term use of high doses of B6 and B12 was associated with a two to four-fold increased risk of lung cancer compared to the risk of the disease in men and didn’t take the vitamins.
The risk was even higher among men who smoked and took more than 20 milligrams (mg) of B6 or 55 micrograms (mcg) of B12 daily for 10 years. Those taking these B6 doses were three times more likely to develop lung cancer, and those taking these B12 doses were approximately four times more likely to develop the disease than men who didn’t take the vitamins. (No increased risk was seen in female participants.)
The study doesn’t prove that taking the B vitamins caused lung cancer, but it does show an association between these doses and development of the disease in men. The researchers weren’t sure how the vitamins influenced the risk of cancer, although study leader Theodore Brasky of Ohio State University suggests it might be related to their influence on male hormones.
Keep in mind that the latest study showed an association with lung cancer risk and these B vitamins when they were taken as individual supplements, but did not find such an association with taking multivitamins or B vitamins from dietary sources. Previous studies, including the European Prospective Investigations into Cancer and Nutrition (EPIC) study, a large trial published in JAMA in 2010, demonstrated that higher blood levels of B6 were associated with a lower risk of lung cancer.
Good food sources of B6 include brewer’s yeast, bananas, cereal grains, legumes, vegetables (especially carrots, spinach and peas), potatoes, milk, cheese, eggs, fish and sunflower seeds. I recommend 50 mg of vitamin B6 as part of a daily B-complex supplement that contains a full spectrum of B vitamins, including thiamin, vitamin B12, riboflavin and niacin.
Even before the association of B6 with lung cancer in men, we knew that high doses can, over time, be toxic, and may result in nerve damage or numbness and tingling in the extremities that may eventually be irreversible. Be sure to discontinue use if any unusual numbness develops in the body. Learn more about vitamin B6 for brain health.
The best food sources of vitamin B12 are dairy products, eggs, meat, fish, poultry and shellfish. I recommend taking 50 mcg as part of a B-complex supplement that also contains a full spectrum of B vitamins, including biotin, thiamin, riboflavin, and niacin.
The clear message from the Ohio State investigation, and many other studies, is that not smoking is the best thing you can do to prevent lung cancer.
Andrew Weil, M.D.
Theodore M. Brasky et al, “Long-Term, Supplemental, One-Carbon Metabolism–Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort.” Journal of Clinical Oncology, August 22, 2017, doi.org/10.1200/JCO.2017.72.7735