No link seen between meat and risk of brain cancer

NEW YORK (Reuters Health) - Despite theories to the contrary, adults who eat a lot of meat may not have a heightened risk of the most common type of malignant brain tumor, a new study finds.

The study, reported in the American Journal of Clinical Nutrition, looked at the potential link between brain tumors called gliomas and people's intake of meat and compounds called nitrosamines.

Nitrosamines, which are potentially cancer-promoting, are present in certain foods, or are formed in the body other chemicals we eat called sodium nitrites and nitrates. These compounds are used in preserving and flavoring processed and cured meats -- like hot dogs, bacon, sausage and ham -- which makes those foods major sources of dietary nitrosamines.

For several decades, researchers have thought that nitrosamines -- which can cross from the blood to the brain -- may contribute to the risk of gliomas, a group of brain tumors that makes up about 80 percent of malignant brain cancers in adults.

But studies so far have come to inconsistent conclusions.

For the new study, researchers used data from three large ongoing health studies of U.S. doctors and nurses whose diets and lifestyle habits have been periodically surveyed for up to three decades.

They found that among the nearly 238,000 men and women in the studies, just 335 were diagnosed with gliomas at some point. There were no links between the risk of developing the disease and participants' intake of meat, processed meat, nitrites, nitrates or nitrosamines.

What's more, there was no elevated risk among meat lovers who also had low intakes of antioxidants like vitamins C and E -- which slow down the formation of nitrosamines in the stomach.

"As always with results from one single study, we need to be cautious with interpretation," lead researcher Dr. Dominique S. Michaud, of Imperial College London in the UK, told Reuters Health in an email.

However, she said, "this study suggests that at least in adulthood, meat intake probably does not increase the risk of glioma." Whether diet during childhood and adolescence has any later impact is unknown, Michaud noted.

Even if there is no connection to glioma risk, though, there are still plenty of other health reasons to limit red and processed meats in the diet, Michaud pointed out. Studies have linked high intakes to a number of diseases, including heart disease and colon, stomach and breast cancers.

SOURCE: American Journal of Clinical Nutrition, September 2009.