Researchers also report that the amino acid methionine, which is found in most protein, may also reduce the risk of lung cancer.
“Given their involvement in maintaining DNA integrity and gene expression, these nutrients have a potentially important role in inhibiting cancer development, and offer the possibility of modifying cancer risk through dietary changes,” wrote the authors in the Journal of the American Medical Association.
One in three Europeans are smokers, while the US figure is one in five. Tobacco smoke contains over 4,000 compounds, of which 60 are known carcinogens. The oxidative stress levels of smokers are significantly greater than non-smokers, and as such there is a bigger drain on the levels of antioxidants in the body.
Furthermore, the new study indicated that folate may also be beneficial, and that high folate levels combined with methionine and B6 were associated with a 66 per cent reduction in lung cancer risk.
Led by Paul Brennan from the International Agency for Research on Cancer in Lyon, France, the researchers used data from 385,747 people who donated blood while participating in the European Prospective Investigation into Cancer and Nutrition (EPIC). Out of this, 899 people with lung cancer were identified and matched with 1,770 cancer-free people.
The researchers noted that increasing blood levels of vitamin B6 were associated with lower risks of lung cancer. A similar risk reduction was observed for methionine, which extended to never, former, and current smokers. This indicated that smoking habits were not confounding the results.
“Our results suggest that above-median serum measures of both B6 and methionine, assessed on average 5 years prior to disease onset, are associated with a reduction of at least 50 percent on the risk of developing lung cancer,” wrote the researchers. “An additional association for serum levels of folate was present, that when combined with B6 and methionine, was associated with a two-thirds lower risk of lung cancer,” they added.
More research needed
Correlation does not prove causation, however, and more research is needed to clarify the role of B vitamins and methionine in lung cancer, said the researchers.
“It is essential that for lung cancer prevention, any additional evidence about causality does not detract from the importance of reducing the numbers of individuals who smoke tobacco,” wrote Brennan and his co-workers
“With this in mind, it is important to recognize that a large proportion of lung cancer cases occur among former smokers, making up the majority in countries where tobacco campaigns have been particularly successful, and a non-trivial number of lung cancer cases occur also among never smokers, particularly among women in parts of Asia.
“Clarifying the role of B vitamins and related metabolites in lung cancer risk is likely therefore to be particularly relevant for former smokers and never smokers,” they concluded.
2010, Volume 303, Number 23, Pages 2377-2385
“Serum B Vitamin Levels and Risk of Lung Cancer”
Authors: M. Johansson, C. Relton, P.M. Ueland, et al.