Folate supplementation during pregnancy may increase a mother's long-term risk of breast cancer

Preliminary data published in the BMJ suggest that folate supplementation during pregnancy may increase a mother's long-term risk of breast cancer. Although this may be a chance finding, the results require confirmation, say the authors.

During pregnancy, folate plays an important part in fetal growth. Research has shown that taking folate before conception and during early pregnancy reduces the risk of neural tube defects, but there is limited evidence on the long-term effects of increased folate intake in pregnancy.

The research team from Aberdeen and Bristol followed up 2,928 pregnant women enrolled in a trial of folate supplementation in the 1960s. The women were randomly assigned to receive a daily dose of folate (0.2mg), folate (5mg), or a dummy (placebo) tablet. Factors such as age, weight, blood pressure, and smoking habits were recorded and blood samples were taken.

By the end of September 2002, 210 women had died with 40 deaths attributable to cardiovascular disease, 112 to cancer and 31 to breast cancer.

The team found that in women randomised to high dose folate supplements, all cause mortality was around 20% higher and the risk of deaths attributable to breast cancer was two times greater.

Although this was a well conducted randomised trial, these findings are preliminary and could be due to chance, stress the authors.

The report's author Dr Andy Ness said: "our paper presents preliminary findings which are intended to point the way towards further research and it is published on that basis. It is entirely possible that this is a chance finding - so further scientific studies are required to examine the association, if there is one, before we reach any conclusions."

"It is important that we don't confuse women about the need to take folic acid supplements early in pregnancy. Women planning to become pregnant should take folic acid supplements as recommended as there is a considerable difference between the Aberdeen trial and the current guidelines to prospective mothers."

The most likely explanation for these results is chance, argue public health experts from the United States in an accompanying commentary. They cite several studies suggesting that folic acid is likely to prevent breast cancer rather than to cause it.

They also believe that this report should not deter mandatory folic acid fortification of wheat and corn flour around the world. "Mandatory fortification should be immediately implemented for the known benefits of preventing birth defects and anaemia," they conclude.

Contacts:
Paper: Andy Ness, Senior Lecturer in Epidemiology, Unit of Paediatric & Perinatal Epidemiology, Bristol, UK
Tel: Nick Kerswell, University of Bristol +44 (0)117 331 6731 Out of office hours: +44 (0)1275 474 502 or +44 (0)7967 390 808
E-mail: [email protected]

Commentary: Godfrey Oakley, Research Professor, Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
Tel: +1 404 727 2656; Mobile: +1 678 613 6918
E-mail: [email protected]

Click here to view full paper