Could B Vitamin Megadoses Increase Actually Lung Cancer Risk For Male Smokers?

Posted August 24, 2017

The risk of lung cancer nearly doubled for men who took the highest doses of 10-year average daily dose of vitamin B6 ( 20 mg/day; hazard ratio [HR], 1.82; 95% CI, 1.25-2.65) and vitamin B12 ( 55 μg/day; HR, 1.98; 95% CI, 1.32-2.97), compared to non-users.

Why B vitamins influence cancer risk is not known for sure, but some believe that it is related to how B vitamins interact with the so-called one-carbon-metabolism pathway. Upon enrollment, they reported their B-vitamin usage from the previous 10 years, as well as dosage information.

The risks of developing lung cancer were even higher for men who take the supplements and also smoke, according to the study, which was published this month in the Journal of Clinical Oncology. However, the risk was found only among men, not women.

Vitamin B provides protection against diseases but it is a "double-edged sword" as taking this vitamin in high doses may increase risk of lung cancer, according to a new study.

Theodore Brasky, PhD, research assistant professor at The Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, and colleagues adjusted their analysis for several factors, including smoking history, age, race, body size, alcohol consumption, personal history of cancer or chronic lung disease, family history of lung cancer and use of anti-inflammatory drugs. "This is certainly a concern worthy of further evaluation".

"That's marketing. That's not science", Brasky noted. Dr. Kourosh Ahmadi with Surrey University says it is highly unlikely very many people are taking the vitamins above the recommended daily allowance. We were unable to address whether lung cancer patients had improved or worsened prognosis if they took these supplements.

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B vitamins - B-6, B-9 (folate), and B-12 - are commonly thought to reduce cancer risk, among other benefits.

Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC - James), Fred Hutchinson Cancer Research Center and National Taiwan University report their findings in the August 22, 2017 issue of the Journal of Clinical Oncology.

"If you look at B-vitamin supplement bottles. they are anywhere between 50-fold the USA recommended dietary allowance (to) upward of 2,100-fold", Brasky said. Some studies linked vitamin B6 with lower lung cancer risk, and another found that B12 had no impact on risk. Results revealed that just over 800 of the study volunteers developed lung cancer over an average follow-up of six years.

Many feel that the world of dietary supplementation needs regulating.

Disclosures: The NCI, NIH and Office of Dietary Supplements funded this study.

Risk was further elevated in male smokers taking more than 20 mg of B6 or 55 micrograms of B12 a day for 10 years. The researchers report no relevant financial disclosures.