It doesn’t mean you should start popping handfuls of B vitamins if you are a smoker or a former smoker (those who never smoked rarely get the disease). What it appears to mean is that people with the highest levels of vitamin B6 in their bodies may have as little as half the risk of developing lung cancer as people with very low levels of B6--also known as pyridoxine.
In a June 16 article in theJournal of the American Medical Association (JAMA) , dozens of researchers from around the world deconstructed a European medical database from the 1990s, containing medical data and blood test results for more than 380,000 people. They were looking for meaningful statistical correlations having to do with the 899 people in the study who eventually developed lung cancer.
According to Nathan Seppa in Science News, the international research team found that “people with vitamin B6 levels ranking in the top one-fourth of all the samples taken had less than half the risk of lung cancer as those with the lowest vitamin B6. A similar comparison found that people with high levels of [the amino acid] methionine seemed to have almost half the cancer risk of people with low levels. High folate levels seemed to give less protection.” The researchers calculated that having high levels of all three compounds could reduce lung cancer risk by as much as two-thirds.
Much remains unknown. Can smokers use B6 vitamin supplements to protect against lung cancer, or are the protective effects, if verified, due to a B6 level that reflects diet and other metabolic factors at work over decades? And, as always, there is the question of B6 from vitamin supplements vs. B6 from B6-rich foods like fish, beans, and grains.
A smaller prospective study undertaken in 2001 came up with similar results. Published in the American Journal of Epidemiology, the study involved 300 lung cancer patients in Finland between 1985 and 1993. The researchers looked at B6, B12, and folate, and found “significantly lower risk of lung cancer among men who had higher serum vitamin B6 levels. Compared with men with the lowest vitamin B6 concentration, men in the fifth quintile had about one half of the risk of lung cancer.” The researchers speculate that one of the mechanisms by which B6 could influence carcinogenesis is the role the vitamin plays in homocysteine metabolism. B6 is involved in the complex process of metabolizing homocysteine, another amino acid. Absent sufficient B6, homocysteine levels can build up in the body, causing heart disease and other ailments.
Mattias Johansson, et. al. (2010). Serum B Vitamin Levels and Risk of Lung Cancer Journal of the American Medical Association, 303 (23), 2377-2385