Folic acid in dietary supplements could increase risk of breast cancer, Swedish research suggests

"Therefore I think it is too soon to introduce a general fortification of foodstuffs with folic acid," says nutrition researcher Ulrika Ericson of Lund University. Neither does she think it is a good idea to take multivitamin tablets and other dietary supplements containing folic acid (the synthetic form of folate) without special reason.

"It is better to eat a diet containing a lot of fruit, vegetables, legumes and wholemeal products. Then you get sufficient quantities of the natural form of folate, other vitamins and dietary fibre."

In her doctoral thesis, Ulrika Ericson has taken as her starting point the major study from the 1990s, Malmö Diet and Cancer, which gathered information and blood samples from over 17 000 women. At the end of 2004, just over 500 of these women had developed breast cancer. Folate levels, genetic make-up and food habits in the breast cancer patients have then been compared with the corresponding data from the healthy women.

Those women whose intake of folate corresponded to the level recommended in Sweden had only half as great a risk of getting breast cancer as those who had the lowest intake of folate. This was the overall finding, which shows that folate generally protects against breast cancer. However, the breast cancer risk increased in line with folate levels for a specific sub-group among the women -- those who had inherited a certain variant of an enzyme that affects how folate is used in the body. The ten per cent of the women who had inherited this variant from both of their parents had the highest risk of breast cancer, particularly if they also took vitamin tablets containing folic acid.

"No-one knows which genetic variant of this enzyme they have. This is why I think people should only take dietary supplements if there is a particular reason to do so, not just because 'it's probably a good idea'," says Ulrika Ericson.

She considers that there are two groups who could have a particular reason to take a folic acid supplement. These are people with a certain type of anaemia and low folate levels and women who are trying to become pregnant (folate reduces the risk of naural tube defects in babies). To be on the safe side, others should avoid vitamin tablets containing folic acid while it is still unclear what the link is between folate and different types of cancer. Mandatory folic acid fortification of foodstuffs, which has been discussed in many countries including Sweden, is not appropriate in the current situation, according to Ulrika Ericson.