Folate is a water soluble B-vitamin present naturally in foods such as wholemeal bread, legumes, green leafy vegetables (e.g. broccoli, lettuce and cabbage) and liver that is essential for biochemical and physiological processes in the body.
Voluntary fortification of certain foods with folic acid has been permitted in New Zealand and Australia since January 1996 to help reduce the incidence of neural tube defects. Mandatory folic acid fortification of wheat flour for bread-making purposes commenced in Australia from September 2009. Voluntary fortification of bread with folic acid commenced in New Zealand in 2009 and is currently permitted under the New Zealand (Permitted Fortification of Bread with Folic Acid) Food Standard 2012.
There is probable evidence that foods containing folate reduce the risk of pancreatic cancer and limited suggestive evidence that they reduce the risk of oesophageal and bowel cancer. Cohort studies suggest that a high dietary folate intake may reduce the risk of post-menopausal breast cancer, particularly for women with a family history of breast cancer. There does not appear to be any significant association between folate intake and the risk of lung cancer, and limited evidence suggests there is no association between folate intake and ovarian, stomach and prostate cancer.
A small number of recent studies, while inconclusive, suggest that high doses of folic acid as a supplement may promote the progression of undiagnosed premalignant and malignant lesions of the bowel. While dietary folate (even from foods fortified with folic acid) may have no adverse effects, some studies suggest that the combined impact of folic acid from supplements and fortification could promote pre-existing bowel adenomas.
Based on current evidence, the benefits of folic acid fortification for reducing the incidence of neural tube defects outweigh any potential increased risk of cancer. Therefore the Cancer Society of New Zealand and Cancer Council Australia are not opposed to mandatory fortification of foods with folic acid. However careful monitoring of emerging evidence on any adverse effects of folic acid fortification, particularly cancer incidence, is required.
The Cancer Society of New Zealand and Cancer Council Australia support the respective government guidelines for food and nutrition (New Zealand Food and Nutrition Guidelines and Australian Dietary Guidelines) and recommend people obtain their nutritional requirements from whole foods, such as fruits, vegetables, breads and cereals rather than individual nutrients in a supplement form.
People with existing bowel adenomas and those with an increased risk of developing bowel adenomas should avoid taking high-dose supplements that contain folic acid.
See the full position statement:
Folate and Cancer Risk Position Statement