Pros and cons of increasing folic acid and vitamin B12 intake by fortification.

There is no doubt that folic acid fortification can be effective for reducing the incidence of neural tube defects. The degree of efficacy depends on both the level of folate depletion and other, yet to be fully characterized, genetic and/or environmental factors. This article summarizes briefly data on neural tube defect reduction and other benefits of folic acid fortification as these have been reviewed in more detail elsewhere. More attention is drawn to questions that have been raised about the possible adverse effects of folic acid fortification including the incidence of colorectal cancer and immune function. The main question addressed here is whether folic acid fortification can exacerbate the adverse effects of vitamin B12 deficiency. Most analyses of this question have been conducted in wealthier countries based on data from elderly populations - which have the highest prevalence of vitamin B12 deficiency. However, of potentially greater concern is the increasingly common practice of folic acid fortification in developing countries, where folate status is probably often adequate even prior to fortification, and vitamin B12 depletion or deficiency is common. To add to this information, data from a group of Chilean elderly with a range of vitamin B12 status and exposed to high levels of folic acid fortification will be presented.