There's no conclusive evidence that folic acid supplements improve cognitive function in older adults or in people with Alzheimer's disease or other types of dementia.

Blood levels of folate are classified as either low or normal in the general population. Low folate blood levels are associated with poor cognitive performance, which could be improved by folic acid supplements. However, folic acid is not helpful for people with normal blood levels.

Reviews of randomized, controlled trials have shown mixed results about whether folic acid supplements have a benefit on cognitive function in healthy adults or in those with mild to moderate cognitive decline or dementia. This is an active area of research.

So although it doesn't appear that a folic acid supplement would benefit everyone, it may be something worth discussing with your doctor. Keep in mind that in the United States many foods, such as breads and cereals, are fortified with folic acid. Many people also take a multivitamin, the majority of which have extensive B complex vitamins such as B12 and folate.

If you're at high risk of developing dementia or have already experienced some cognitive decline, checking your folic acid levels may be a reasonable step.