Folate, also called folic acid or vitamin B-9, is one of the essential B-complex vitamins. It plays an essential role in the development of the precursors to the nervous system during embryonic development, and it also aids in the production of energy within your cells. While consuming enough folate each day helps maintain your health, consuming too much folic acid via dietary supplements can prove harmful.
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Upper Intake Limit
To help prevent an accidental folic acid overdose, the Institute of Medicine Food and Nutrition Board has developed an upper tolerable limit for the vitamin. Consuming less than the upper limit does not typically cause vitamin overdose, while exceeding the limit can harm your health. The board recommends that men and women over the age of 19 not consume more than 1000 mcg of the vitamin each day. If you take multivitamins or folic acid supplements, consume the vitamin only at a level recommended by your doctor.
Interaction with Vitamin B-12
One of the risks of overdosing on folic acid comes from its interaction with vitamin B-12, or cobalamin. Normally, cobalamin deficiency leads to a blood disorder called megaloblastic anemia, which doctors often use to identify and diagnose a vitamin B-12 deficiency before it causes more permanent tissue damage. Overdosing on folic acid can prevent the development of this anemia, without correcting the underlying vitamin B-12 deficiency, according to the Office of Dietary Supplements. As a result, folic acid overdoses can delay or prevent doctors from treating a vitamin B-12 deficiency.
Symptoms of Folate Overdose
The dangers of folic acid overdose come from its ability to mask vitamin B-12 deficiency. Long-term cobalamin deficiency can harm your nervous system. Damage to the nerves throughout your body can lead to numbness and tingling, as well as the destruction of myelin -- a substance required for nerve function -- in your spinal cord and brain, according to the Linus Pauling Institute at Oregon State University. This nerve damage proves irreversible, so long-term over-consumption of folic acid might permanently affect your health.
You can avoid a folic acid overdose by consuming vitamin B-9 in your food, since you're unlikely to overdose on folic acid from just dietary sources. Spinach, orange juice and vitamin-fortified cereals all contain folic acid, and consuming a balanced diet can help you consume enough vitamin B-9. If you do take folic acid supplements, you should also undergo medical testing to check your vitamin B-12 level to ensure you don't have a deficiency, and take the vitamin B-9 supplement at the dose recommended by your doctor.
- Institute of Medicine Food and Nutrition Board: Dietary Reference Intakes (DRIs): Tolerable Upper Intake Levels, Vitamins
- Office of Dietary Supplements: Folate
- Linus Pauling Institute; Vitamin B12; Jane Higdon; March 2003
- University of Maryland Medical Center; Vitamin B9 (Folic Acid); Steven Ehrlich; May 2009