It is well known that taking folic acid before and during pregnancy helps prevent 'neural tube defects', developmental disorders such as spina bifida. However, the wisdom of this practice was recently called into question when a study appeared to link folic acid supplements with a substantially increased risk of breast cancer later in life. Widespread media reporting of this study seemed to leave little doubt that women trying to ensure a healthy pregnancy might be jeopardising their own health.

However, because the manner in which scientific data is translated by journalists does not always tell the full story, I resolved to look at this in some depth. The study in question was a follow-up to research conducted in the Sixties in which the effects of folic acid were assessed in about 3,000 pregnant women. Women were given either 200mcg of folic acid, 5,000mcg (5mg) of folic acid or a placebo each day. About 35 years later, the health of these women was reassessed. The results, published in the British Medical Journal, showed that women taking the higher dose of folic acid appeared to be at twice the risk of dying from breast cancer.

While stark, these statistics do not, however, prove a definite link between folic acid and breast cancer. The total number of breast cancer cases in those who had taken 5,000mcg of folic acid was just eight. With such a small number of cases, it is quite possible that the association is due not to real effect, but to chance. In fact, standard analysis revealed that this apparent doubling in risk of breast cancer was not statistically significant.

The authors of the BMJ study admit that the apparent link between folic acid and breast cancer might be due to chance. And the authors of a commentary on the study state that chance is the 'most likely explanation for the reported association'. Unfortunately, the inconclusive nature of the original study did not seem to temper the media reports. My fear is that folic acid's recent bad press may erode trust in this nutrient.

Despite the attention it attracted, it is clear that the BMJ study does not give good reason to lose faith in folic acid. Foods rich in folate, such as green leafy vegetables, beans and lentils, should be emphasised prior to and during pregnancy. I also recommend that women continue to supplement 400mcg of folic acid each day. Because neural tube defects form early in pregnancy, supplementation should ideally start at least a month prior to conception, and continue for the first three months of pregnancy. The evidence still shows that folic acid supplementation has the capacity to deliver the goods.