Pancreatic cancer, arguably one of the deadliest forms of cancer with just a 4 percent survival rate over five years, could possibly be prevented by increasing levels of dietary folate, Reuters reports of a very large, population-based study of men and women from the Karolinska Institute in Stockholm.

There is just one catch: The folate must come food and not vitamin supplements. Why? Supplements don't seem to make a difference and might even be harmful.

Folate, which is also called folic acid, is a B vitamin found naturally in spinach, asparagus, chickpeas, kidney beans and lentils and added to numerous grain products, such as flour, rice, pasta, cold cereals and cornmeal. Previous research has shown it may protect us from colorectal and breast cancer.

The study: Led by Dr. Susanna C. Larsson, the Swedish team followed 36,616 women and 45,306 men who were between 45 and 83 years old in 1997 to determine if folate also protects against pancreatic cancer. The subjects were already enrolled in the Swedish Mammography Cohort or the Cohort of Swedish Men for which they had completed food frequency questionnaires. The group was followed for 6.8 years, and during that time 135 cases of pancreatic cancer occurred.

The results: Even when such influences as demographics, smoking, body mass index, diabetes, exercise and the amount of dietary fruit, vegetables, calories, carbohydrates and alcohol were factored in, those who consumed the most dietary folate (350 micrograms per day or more) were 75 percent less likely to develop pancreatic cancer, compared with those who had the lowest intake (200 micrograms per day). Folate derived from supplements had no effect.

Why does the folate have to be from food to work? Larsson speculates that food sources better represent long-term folate intake than do the supplements, which may be taken for only a short time. In addition, high quantities of folate supplements may actually promote the progression of cancer if it's already there.

The study findings were published in the Journal of the National Cancer Institute.