Increased levels of dietary folate from food, but not from supplements, appears to reduce the risk of developing pancreatic cancer, according to results of a large population-based study of Swedish men and women.
Folate, also known as folic acid, is a B vitamin that is naturally found in fruits and vegetables. The US government recently mandated that manufacturers fortify grain products with folic acid, adding it to flour, rice, pasta and cornmeal.
Previous studies have suggested that folate may protect against colorectal and breast cancer, Dr. Susanna C. Larsson and colleagues note in their report, published in the Journal of the National Cancer Institute.
To see if folate protects against pancreatic cancer too, Larsson, from Karolinska Institute in Stockholm, and her group followed subjects enrolled in the Swedish Mammography Cohort or the Cohort of Swedish Men. Included were 36,616 women and 45,306 men between 45 to 83 years old in 1997, when they completed food frequency questionnaires.
After a follow-up of 6.8 years, 135 cases of pancreatic cancer had occurred. The investigators analyzed the data, factoring in the influence of demographics, smoking, body mass index, diabetes, exercise and the amount of dietary fruit, vegetables, calories, carbohydrates and alcohol.
For subjects with the highest amount of dietary folate intake (350 micrograms per day or more) were 75% less likely to develop pancreatic cancer compared with subjects with the lowest amount of dietary folate (less than 200 micrograms per day).
However, there was no association between folic acid derived from supplements and pancreatic cancer risk – subjects who took folate supplements of 300 micrograms per day or more versus subjects who did not take supplements had the same risk.
Larsson’s group theorizes that the reason that dietary folate alone reduced the risk of pancreatic cancer may be that folate from food sources better represents long-term folate intake than does folate from supplements.
Another possibility, suggested by animal studies of high folic acid supplementation, is that high intake of folate from supplements may promote the progression of cancer if it is already there.
“Although our results suggest that increased consumption of foods naturally rich in folate may be beneficial,” the authors conclude, “they do not encourage increased use of supplements for the prevention of pancreatic cancer.”