Is a high carbohydrate diet linked to pancreatic cancer?

NEW YORK (Reuters Health) - One of the first symptoms of pancreatic cancer -- often noticed even years before diagnosis -- is indigestion. A new study suggests that these timely tummy troubles may be enough to explain away previous links made between a high carbohydrate diet and an increased risk of the disease.

“We started out just aiming to replicate other studies that looked at the association between carbohydrates and pancreatic cancer,” Rachael Stolzenberg-Solomon, from the National Cancer Institute, Bethesda, Maryland and an investigator on the new study, told Reuters Health. “But it turned out to be something more interesting.”

It also turned out to be more complicated.

Like many of the prior studies, Stolzenberg-Solomon and her colleagues did initially find evidence of a link between a high carbohydrate diet and pancreatic cancer among more than 100,000 older men and women. The top 10 percent of the participants in rankings of carbohydrate consumption had an almost 50 percent greater risk of the cancer than the bottom 10 percent, the investigators report in the American Journal of Epidemiology.

It’s important to note, however, that even with this increase in pancreatic cancer risk, the risk remained extremely low. Pancreatic cancer is rare: less than one-quarter of 1 percent of all participants were diagnosed over about a 7-year study period.

But what got the researchers’ attention was how this apparent increase in risk was limited to carbohydrate consumers followed fewer than 4 years.

The researchers only collected information on food intake at the start of the study. And follow-up ended when a cancer diagnosis was made. So those participants diagnosed early on, explained Stolzenberg-Solomon, may have already been suffering cancer-related indigestion when they filled out the dietary questionnaire.

Further, since fatty foods can exacerbate indigestion, they may have replaced some of the fat in their diet with more easily digestible carbohydrates. Stolzenberg-Solomon recalled that a fat-carbohydrate swap was common among the pancreatic cancer patients she saw during her previous work as a dietitian.

In other words, carbohydrate intake may be a consequence rather than a cause of pancreatic cancer.

“It’s all very complex,” noted Stolzenberg-Solomon. “But it’s one possible explanation for this change in risk between 3 and 4 years.”

The finding could shed light on inconsistent results from previous studies that may not have been as careful or detailed in their data collection, Kristin Anderson, of the University of Minnesota and a co-author on other recent pancreatic cancer studies, told Reuters Health in an email: “You can’t try to understand a puzzle by looking at one piece.”

SOURCE: here

American Journal of Epidemiology, online May 7, 2010.