Smokers who have higher levels of vitamin B6 in their blood, as well as a little-known amino acid called methionine, appear to have a lower risk of developing lung cancer, new research suggests.

But the authors of the study are quick to note that the study didn't establish cause and effect, and more study will be needed before smokers should consider loading up on B6 in an effort to prevent cancer.

The study of nearly 520,000 adults from 10 European countries was conducted by scientists at the International Agency for Research on Cancer (IARC). They recruited the participants between 1992 and 2000, and had more than 385,000 offer blood samples.

The researchers focused on 899 volunteers who developed lung cancer. Most of them were smokers but about 100 had never smoked and 260 had quit. They then compared them to 1,770 similarly matched people who hadn't developed lung cancer.

The researchers found that those volunteers with the highest levels of vitamin B6 in their blood samples (which were taken, on average, five years before the volunteers developed cancer) were 56 per cent less likely to have developed lung cancer than those with the lowest levels.

Those with the highest levels of methionine were 48 per cent less likely to have developed the disease compared to those with the lowest concentrations.

For the two nutrients together, the risk reduction was about 60 per cent.

"Similar and consistent decreases in risk were observed in never, former, and current smokers, indicating that results were not due to confounding [factors that can influence outcomes] by smoking," the researchers write in JAMA, the Journal of the American Medical Association.

As for how vitamin B6 might be related to lower cancer risk, that remains unclear.

It is known that B6 helps the body construct and maintain DNA, as well as process glucose (sugar) in the blood. It's also possible that some other factor related to the vitamin and amino acid affected the results, such as other elements in specific foods high in B6 and methionine.

Lung cancer remains the most com¬mon cause of cancer death in the world today, with about 90 per cent of cases due to smoking. About 15 per cent of smokers will develop lung cancer, compared to just two per cent in the rest of the population.

IARC's Dr. Paul Brennan who led the study, said even if a cause and effect relationship is found between vitamin B6 and lung cancer, the most important factor to reducing lung cancer deaths still remains smoking prevention.