The nutrient folic acid is generally good for brain health, but research now suggests that too much of it might harm people who get too little vitamin B12. Those potentially at risk include vegetarians, whose diets may contain insufficient B12, and elderly people, who tend to absorb the vitamin inefficiently.
Intake of folic acid, or folate, is higher in the United States than in most countries in part because U.S. food manufacturers have been legally obligated since 1998 to add it to grain products, such as baked goods and breakfast cereals.
The fortification policy exists because folic acid, when consumed by women around the time they conceive, prevents serious congenital malformations called neural tube defects. Moreover, studies suggest that folic acid can safeguard neurological health in older people.