However, new research published last January in the American Journal of Clinical Nutrition provides the first inkling that folic-acid fortification may be a problem for older people. The trouble stems from the vitamin’s close relationship with vitamin B12, which your body becomes less able to process as it ages. If you are deficient in B12—a problem more common after age 55—folic-acid megadoses can mask the early symptoms that warn of the B12 deficiency. Left undetected and thus untreated, B12 deficiency can lead to irreversible nerve and brain damage.
When Martha Savaria Morris, Ph.D., and her colleagues at Tufts University reviewed data from 1,459 elderly people (average age 70) who participated in a recent federal nutrition survey, they found that about one-quarter of them were low in vitamin B12. Within this group, those who also had the highest blood levels of folate were five times more likely to have symptoms of advanced B12 deficiency—including slower responses on a standardized test that measured ability to combine numbers with symbols—than those with lower folate levels.