But cause-and-effect not clear, and supplements are no excuse to keep smoking, experts say
TUESDAY, June 15 (HealthDay News) -- A new study shows that people with high levels of a B vitamin are half as likely as others to develop lung cancer. But while the reduction in risk is significant, this doesn't mean that smokers should hit the vitamin aisle instead of quitting.
While the study links vitamin B6, as well as one amino acid, to fewer cases of lung cancer, it doesn't conclude that consuming the nutrients will reduce the risk. Future research is needed to confirm that there's a cause-and-effect relationship at work, not just an association, researchers said.
The research "may lead to important new discoveries. But people should not think that they can pop a few vitamins and be safe smoking," stressed Dr. Norman Edelman, the American Lung Association's chief medical officer.
The findings appear in the June 16 issue of the Journal of the American Medical Association.
The researchers examined a study of almost 520,000 Europeans who were recruited between 1992 and 2000. They compared 899 who developed lung cancer by 2006 to 1,770 similarly matched people who hadn't developed the disease.
The researchers found that those with the highest levels of vitamin B6 in their blood were 56 percent less likely to have developed lung cancer than those with the lowest levels. There was a similar difference -- a 48 percent decline -- for those with the highest levels of methionine, an amino acid, compared to those with the lowest concentrations.
The reductions in risk held up for both smokers and non-smokers, said study co-author Paul Brennan, a researcher with the World Health Organization's International Agency for Research on Cancer in Lyon, France.
Normally, as many as 15 percent of lifetime smokers will develop lung cancer, but fewer than 1 percent of those who never smoke do, Brennan said.
The reduction in risk is impressive and it could be a step forward toward greater understanding of how food and medications may prevent lung cancer, said the ALA's Edelman. "That's a whole new field, and it's just beginning to become something that's actually being studied," he said.
Both vitamin B6 and methionine are important to good health and available in supplement form.
Vitamin B6 helps the body protect itself against disease and process glucose (sugar) in the blood; it's found in foods such as bananas, fish, chicken, potatoes, peanut butter and fortified cereal. Methionine is found in foods such as red meat, fish and beans. People can suffer from methionine deficiency, which can cause medical problems, including liver damage.
However, the experts said that it's possible that some other factor related to the vitamin and amino acid is affecting the lung cancer rate, such as a specific food that they are found in.
If vitamin B6 and methionine really do lower the risk of lung cancer, researchers aren't sure of the mechanism. However, both nutrients are linked to the body's construction of DNA, and lowered levels might lead to errors, Brennan theorized.
So should you take supplements to boost the levels of vitamin B6 and methionine, just in case? No, Brennan said. "There is no evidence that vitamin supplements may reduce cancer risk and even some evidence that they may increase cancer risk," he said.
Instead, he made the usual recommendation: eat right. "At this stage, we would recommend that people stick with usual dietary recommendations for a healthy diet. This study does not change that," Brennan said.
In a related study, also published in the same issue of JAMA, researchers at the University of North Carolina, Chapel Hill, examined the reasons why many lung cancer patients decide against potentially life-extending surgeries.
The team surveyed 437 patients diagnosed with early-stage lung cancer, 386 of whom were eligible for tumor-removing surgery. A total of 241 patients underwent the surgery within four months of their diagnosis.
According to the study, patients were less inclined to opt for surgery if they felt that their diagnosis was less than 90 percent certain; if they felt that their quality of life would be worse in one year because of the surgery; or because they felt there had been poor quality communication about their cancer care. Black patients who had two or more co-existing illnesses or who lacked a regular source of care also tended to opt for surgery less often, as did lower-income white patients compared to more affluent whites, the report said.
There's more on nutrition and cancer risk at the U.S. National Cancer Institute.
SOURCES: Paul Brennan, Ph.D., researcher, World Health Organization International Agency for Research on Cancer, Lyon, France; Norman H. Edelman, M.D., chief medical officer, American Lung Association, Chicago; June 16, 2010, Journal of the American Medical Association
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