High folate intake decreases, not increases, colorectal cancer risk
Dietary fortification or supplementation with folate does not increase the risk of colorectal cancer and may well reduce a person's chance of developing the disease, according to a study recently published in the journal Gastroenterology (2011;141:98-105).
Several prospective epidemiologic studies have already shown high folate intake to reduce the incidence of colorectal cancer. However, noted Victoria L. Stevens, PhD, of the American Cancer Society, and fellow investigators, some evidence exists that consuming high levels of folic acid—the form of folate used for fortification and in supplements—has different effects on biochemical pathways than do natural folates, and might promote carcinogenesis.
To evaluate the link between folate intake and colorectal cancer, Stevens and her team evaluated data from 43,512 men and 56,011 women in the Cancer Prevention Study II Nutrition Cohort. Unlike other studies that only considered the source of folate intake (dietary vs. supplement) and not the chemical form, this project assessed natural folates and folic acid separately.
Folate fortification was fully implemented in the United States in 1998; 1,023 members of this cohort were diagnosed with colorectal cancer between 1999 and 2007.
The analysis revealed that intake of high levels of natural folate or folic acid were not significantly associated with colorectal cancer risk, and in fact, high total folate intake was significantly associated with lower risk. Total folate includes naturally occurring food folate and folic acid from fortified foods and dietary supplements.
The strong relationship between high intake of total folate and lower colorectal cancer risk “suggests that total folate intake is the best measure to define exposure to this nutrient because it encompasses all forms and sources,” explained Stevens in a statement announcing her group's findings.