A major European study involving Newcastle University has found a link between the levels of B-vitamins in the blood and lung cancer.
The breakthrough could aid disease prevention, early diagnosis and save lives.
The investigation, led by the International Agency for Research on Cancer (IARC) and Dr Caroline Relton of Newcastle University, looked at data from 520,000 people over two decades and is published today in the Journal of the American Medical Association.
It shows a reduction in lung cancer risk among people with higher levels of vitamin B6 and methionine.
The observed decrease is large, with risk being more than halved in those with high levels of both, and could suggest ways in which diet could be used to change lung cancer risk.
Dr Relton, a senior lecturer in genetic epidemiology at Newcastle University, who was joint lead author on the paper, said: "We studied people from across Europe. Of the original group 900 developed lung cancer. We compared them with a control group of 1,800 and found a disparity in the levels of B-vitamins in the blood.
"The individuals who developed lung cancer had far less vitamin B6 and methionine in their blood, whether they were a smoker or a non-smoker. In fact we found that people with low levels of B-vitamins are more than twice as likely to develop lung cancer.
"This could be a good way for doctors to predict who may be more at risk from developing lung cancer and therefore help to prevent this form of cancer in the future."
Lung cancer is the most common cancer in the world, with an estimated 1.6 million new cases in 2008, representing 1 in 8 of all new cancers. It is also the most common form of cancer death in the world comprising nearly 1 in 5 of all deaths from cancer.
IARC Director, Dr Christopher Wild, said: "The main priority for lung cancer prevention is to get people who smoke to stop, and to ensure young people do not start. However, in many Western countries up to half of lung cancers now occur among people who have quit smoking or who have never smoked, and in certain parts of the world lung cancer is common among never smokers. This highlights the need to find additional ways to reduce lung cancer risk in these groups."
Tobacco smoking is responsible for at least 8 out of 10 cases of lung cancer, although many of these occur among people who have stopped smoking but remain at increased risk. Identifying ways to reduce lung cancer risk could have important public health benefits, especially among people who have stopped smoking.
Appropriate levels of B-vitamins are vital for the cell to make and maintain DNA and disruption of these processes has been suspected of playing a role in cancer. Foods containing high levels of B-vitamins and related compounds may therefore be important in reducing risk.
Vitamin B9 (or folate) can be found in fruits and green leafy vegetables; vitamin B6 is common in fish, meat, potatoes and whole grains; and methionine is present in various seeds, nuts, cereals, fish and meats. Levels of these nutrients in the blood are determined in part by the diet, so they can be altered by what we eat but more work needs to be done to see how dietary changes or supplements may help in the context of lung cancer.
Dr Paul Brennan of IARC, said: "The size of this study, and the strong association observed, provide confidence that the association is real. Whether they are causing the lower risk, or whether they are a marker of the real causal factor, will require further studies."
(Source: Newcastle University: Journal of the American Medical Association: June 2010)