Epidemiological studies over the past ten years have found a link between the regular consumption of dietary folate and the decreased development of colorectal cancer, the conference of the American College of Nutrition was told.
Dr Joel Mason, of Tufts University, Boston, Massachusetts, US, told delegates of new theories about why folate might be beneficial.
He said folate was critical in biochemical reactions where the carbon compound methyl group was added to large macromolecules such as DNA, and the synthesis of nucleotides.
Dr Mason told the conference in Las Vegas, US, that cancer was believed to arise from the result of unrepaired damage to DNA. An inadequate availability of folate could lead to interference with DNA synthesis requiring the methylation process.
He said research had found that a folate variant containing reductase enzyme, which is present in about 10% of people, had a protective effect on the development of colorectal cancers.
Dr Mason said randomized clinical trials were being conducted to determine whether folic acid supplement could protect against the development of precancerous polyps.
He said that folic acid was included in cereal grain flours to help
prevent neural tube defects, spina bifida and brain development
problems. But it still remained a marginal nutrient in the American
"Only twenty percent of Americans consume the minimal five servings per day of folate-rich fruits and vegetables."
Dr Joel Mason
"Only twenty percent of Americans consume the minimal five servings per day of folate-rich fruits and vegetables," he told the conference.
"For example, fast food meals do not provide a single serving of salad food ingredients. Folate-rich citrus juices are consumed by only 25% of Americans on a given day."
Meanwhile in The Lancet, researchers report a link between dietary fiber supplements and an increased rate of colorectal adenomas.
The multicenter randomized trial from nine European countries and Israel tested the effect of diet supplementation with calcium and fiber. 665 patients with a history of adenomas were assigned to take a calcium supplement, ispaghula husk or placebos.
Follow-up found at least one adenoma in 16% of the calcium group, 20% in the placebo group and 29% among those taking the fiber.
Researcher Claire Bonithon-Kopp, of the European Cancer Prevention Organisation Study Group, Dijon, France, said: "Our study, along with the two American trials, suggests that low-fat, high-fiber diet and supplementation with wheat-bran fiber or ispaghula husk may not be effective strategies for the prevention of colorectal adenoma recurrence.
"However, our findings should not prevent recommendations for high consumption of vegetables, fruits, and cereals, because this approach has potentially beneficial effects on other chronic diseases."
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