Vitamin B6 linked to lowered lung cancer risk

High levels of amino acid methionine also seem to help, study finds

While it may be a bit early to start popping supplements, a new study finds that people with high levels of vitamin B6 may be less likely to develop lung cancer than those with low concentrations. Reporting in the June 16 Journal of the American Medical Association, researchers also note a seemingly protective effect from high levels of the essential amino acid methionine and a weaker healthful effect from high levels of folate, another B vitamin.

It’s not yet established how high amounts of these compounds might protect the body from lung cancer, but all three are involved in the maintenance of DNA. In the vast majority of lung cancer cases, toxic smoke causes the DNA damage and aberrant cell growth that marks the disease.

Researchers tapped into a massive database of medical information and blood test results obtained from more than 380,000 Europeans in the 1990s. Using medical registries, the researchers identified 899 people in the study who had developed lung cancer during 12 years of follow-up. For each cancer patient, the scientists randomly selected as a comparison group two people without cancer from the database — matching these controls to the cancer patients in age, gender, country of origin and time of entry into the study.

Paul Brennan of the International Agency for Research on Cancer in Lyon, France, and an international team of researchers calculated 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 methionine seemed to have almost half the cancer risk of people with low levels. High folate levels seemed to give less protection. But having stellar levels of all three compounds lowered a person’s risk of lung cancer by a full two-thirds, the scientists calculated, after accounting for whether they were a smoker, former smoker, or a never-smoker.

The findings may indicate that long-term exposure to the vitamins is the key, says Graham Colditz, a physician and epidemiologist at Washington University School of Medicine in St. Louis. But that doesn’t mean that simply taking vitamins for a few years would make any difference, he says. “This might reflect diet and internal exposure [to these compounds] in the body over decades before the study began.”

A smaller study published in 2001 similarly hinted at protection against lung cancer by high vitamin B6 levels. More recently, several studies suggested a protective effect of vitamin B6 against colorectal cancer. But tests of folate against cancer have shown mixed results, and little research has been done to date assessing the impact of methionine levels on cancer risk.

Even if the results in the new study are real, it remains unclear whether vitamin supplements could provide the same protection as food sources of vitamin B6 and methionine — or whether natural sources of these compounds would work better, Colditz says. Vitamin B6 is found in beans, grains, meat, poultry, fish and to some extent in fruits and vegetables. The main sources of methionine are animal products, with fruits and vegetables providing less.

In any case, the authors note, further clarification that vitamin B6 actively prevents lung cancer — even in smokers — should not “detract from the importance of reducing the numbers of individuals who smoke tobacco.”

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