Two additional studies are underway at The OSUCCC - James to further evaluate high dose, long-term B6 and B12 supplementation and lung cancer risk.
Dietary sources of vitamin B6 and B12 include fortified cereals and foods that are high in protein. The numerous benefits of B vitamins from food and dietary supplements, including supporting cognition, heart health, and energy levels, are well-established, and this study in the Journal of Clinical Oncology doesn't change those facts.
However, the differences in lung cancer risk between the highest and lowest categories of supplementation use appeared considerably greater among current smokers than recent smokers - defined as those who quit less than 10 years prior - or former smokers, defined as those who quit 10 or more years prior.
Researchers from Ohio State University and the National Taiwan University studied more than 77,000 people aged between 50 and 76 in the US and found that men who took high dosages of vitamins B6 and B12 faced 30 percent to 40 percent increased risk of lung cancer.
Recently, a group of researchers from multiple institutions set out to probe this association in the most detailed study of its kind to date. The participants were recruited from 2000 to 2002, and answered questions about their vitamin use over the previous 10 years. Taking B6 at this dose increased the lung cancer risk by three times and taking B12 at this dose increased it by four times.
"Now if you're a male and you're a smoker, and these findings were proven to be replicated over time, then there would be some concern that you probably don't want to be taking megadoses [of B 6 and B12]", Brasky says. "So there really is no reason to supplement your vitamin B intake at these levels, and certainly not for years on end", he said.
"If anything", Brennan said, "we found a small protective effect that was more apparent among men".
After mean follow-up of 6 years, researchers identified 808 incident invasive lung cancer cases in the cohort.
While the supplements might help those with anemia or celiac disease and prevent them from feeling exhausted, large doses may prove to be very useful for an average healthy person. The authors of the new study said that the discrepancy could be because some of these studies measure B vitamins in the blood and not through dietary surveys, like they did.
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.