As part of my research on fortified grains, I have come across a number of disturbing studies on folic acid. Folic acid, which is in fortified foods and multivitamins, is different than the folate you get from food.
This study shows folic acid fortification may have increased colon cancer in Chile. This study showed that folic acid may increase the risk of prostate cancer, while food folate may decrease the risk. This study suggests folic acid may increase the risk of breast cancer.
Probably the most troubling study I found on folic acid was this one . It showed that 38% of a elderly population had unmetabolized folic acid in their blood. This result was only partially explained by high folic acid intake. The other explanation is that there are genetic differences in the ability to metabolize folic acid.
Folic acid is in just about every multivitamin out there. I have recently seen a couple brands that have started putting folate in the vitamins instead of folic acid. I hope this trend continues.