Possible increase in colon cancer after start of folic acid fortification

The rate of colorectal cancer in Chile may have increased since that country began fortifying wheat flour with folic acid, reports a study in the European Journal of Gastroenterology & Hepatology.

The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

"Our data provide new evidence that a folate fortification program could be associated with an additional risk of colon cancer," according to the new report by Dr. Sandra Hirsch and colleagues of University of Chile, Santiago.

Possible Increase in Colon Cancer after Start of Folic Acid Fortification

The researchers analyzed changes in colon cancer rates since the Chilean government introduced a mandatory program of folic acid fortification of wheat flour in 2000. Several countries have implemented similar policies in recent years, with the goal of preventing spina bifida and other neural tube defects. In Chile, the rate of neural tube defects decreased by 40 percent in the first year after the start of folic acid fortification.

The researchers compared hospital discharge data on colon cancer rates in Chile in four-year periods before and after folic acid fortification: 1992-96 versus 2001-04. Although no causative relationship can be proven, the data suggested a significant "temporal relationship" between folic acid supplementation and colorectal cancer. Reported cases of colon cancer increased by 162 percent in people aged 45 to 64 and by 190 percent in people aged 65 to 79.

After adjustment for other factors, discharge diagnoses of colon cancer in these age groups were two to three times more frequent after the start of folic acid fortification. Most other diseases showed no consistent pattern of changes. There was a small increase in breast cancer, which may have been related to early detection and universal treatment programs for breast cancer.

Evidence Is Weaker than Similar Changes Reported in U.S. and Canada

Chile is the third country to report an apparent increase in colorectal cancer after introducing a national folic acid fortification program. A 2007 paper suggested increases in colorectal cancer after folic acid fortification was introduced in the United States and Canada in the mid-1990s. Chile uses a higher "dose" of folic acid than the two North American countries. Folic acid fortification has not yet been introduced in Europe.

There are other possible explanations for the rise in colon cancer in Chile, including increases in obesity and other risk factors.

Another important limitation of the study was the use of hospital discharge data to identify cases of colon cancer. "Discharge rates are influenced by health care politics, increasing access to healthcare for new strata of the population with increased cancer risk, and so forth," comments Dr. Reinhold Stockbrugger, one of the editors of The European Journal of Gastroenterology & Hepatology. "This study provides only a weak, indirect indication of a causal relationship between folate enrichment and colorectal cancer, though similar to that reported in the U.S. and Canada."