Seniors: Use Caution with Folic Acid Supplements

Beware of the interaction between vitamin B12 and folic acid.

To prevent folic acid from triggering symptoms of vitamin B12 deficiency, intake of supplemental folic acid should not exceed 1,000 mcg per day. Folic acid supplements can correct the anemia associated with vitamin B12 deficiency. Unfortunately, folic acid will not correct changes in the nervous system that result from vitamin B12 deficiency. Permanent nerve damage can occur if vitamin B12 deficiency is not treated.

Since older adults are at greater risk of having a vitamin B12 deficiency, they must be aware of the relationship between folic acid and vitamin B12. If you are 50 years of age or older, ask your physician to check your B12 status before you take a supplement that contains folic acid. If you are taking a supplement containing folic acid, read the label to make sure it also contains B12 or speak with a physician about the need for a B12 supplement.

What is the health risk of too much folic acid?

The Institute of Medicine has established a tolerable upper intake level for folate from fortified foods or supplements (i.e., folic acid) for ages one and above. Intakes above these levels increase the risk of adverse health effects. In adults, to prevent folic acid from triggering symptoms of vitamin B12 deficiency, supplemental folic acid should not exceed 1,000 mcg. Understand that the upper intake level refers to the amount of synthetic folate (i.e., folic acid) being consumed per day from fortified foods and/or supplements.

Folate intake from food is not associated with any health risk. The risk of toxicity from folic acid intake from supplements and/or fortified foods is also low. It is a water-soluble vitamin, so any excess intake is usually lost in the urine. Some evidence suggests that high levels of folic acid can induce seizures in patients taking anticonvulsant medications. Anyone taking such medications should consult with a physician before taking a folic acid supplement.

Selecting a healthful diet

As the 2005 Dietary Guidelines for Americans state, "Different foods contain different nutrients and other healthful substances. No single food can supply all the nutrients in the amounts you need." Green leafy vegetables, dried beans and peas, and many other types of vegetables and fruits provide folate. In addition, fortified foods are a major source of folic acid. It is not unusual to find foods, such as some ready-to-eat cereals, fortified with 100% of the RDA for folate. The variety of fortified foods available has made it easier for women of childbearing age in the United States to consume the recommended amount of folic acid per day from fortified foods and/or supplements.

The large numbers of fortified foods on the market, however, also raise the risk of exceeding the tolerable upper intake level. This is especially important for anyone at risk of vitamin B12 deficiency, which can be triggered by too much folic acid. It is important for anyone who is considering taking a folic acid supplement to first consider whether his or her diet already includes adequate sources of dietary folate and fortified food sources of folic acid.