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Folic acid is important, but take care not to overdo it
How much folic acid should you get? And does it matter where you get it from?
One thing experts agree on is that all women of childbearing age should absolutely get 400 micrograms of folic acid through food, supplements or both. Pregnant women should take 600 micrograms daily, adds Janis Biermann, a health educator at the March of Dimes in White Plains, N.Y. Breast-feeding mothers should get 500 micrograms. And pregnant or regularly breast-feeding women who have already had a child with a brain and spinal cord defect should take 1 milligram (1,000 micrograms).
A recent March of Dimes survey found that only 39% of women of childbearing age were taking multivitamins, Biermann says, even though studies show that if every woman in that group got enough folic acid, the rate of brain and spinal cord defects would drop by 70%.
It's hard to get researchers to go out on a limb with recommendations for other categories of people, however. The trials just haven't been done. And different people have different needs.
"We're still at the beginning of that phase of the research," says Marion Neuhouser, nutritional epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle. "I'm not sure we're ready to make recommendations to the public. It would be irresponsible to say do or don't."
Here are some general guidelines, though.
The Institute of Medicine's Food and Nutrition Board's recommended upper limit for folic acid is 1 milligram, which includes a combination of the synthetic kind as well as natural sources of folate. "That's one thing consumers can really take home," Neuhouser says, "not to get more than 1,000 micrograms."
But that amount could be easy to exceed, when you consider that 3/4 cup of 100% fortified cereal contains 400 micrograms, two slices of sandwich bread contain 50 micrograms, half a cup of boiled spinach has 100 micrograms, four asparagus spears have 85 micrograms and a multivitamin supplement contains 400 micrograms.
Of course, it's always worth talking with your doctor about your needs, depending on your age and underlying health conditions, experts say. The older you get, for example, the more likely you are to have precancerous cells in your organs that could be aggravated by excessive folic acid.
Some researchers suspect -- though they don't yet know -- that synthetic folic acid might act differently in the body and cause more problems than natural folate.
Enzymes in the intestines convert folic acid into usable folate, but the body can process only so much of the synthetic vitamin at once. Excess folic acid gets dumped directly into the bloodstream. Some 80% of vitamin-takers have detectable levels of unprocessed folic acid in their blood, according to a recent study.
Also, folate is a more complex molecule than folic acid and it requires more effort by the body to absorb it, Neuhouser says. So, you absorb a higher dose of folic acid from a fortified food than you would from a whole food with the equivalent amount of folate.
For those reasons and others, nutrition researchers continue to stress the importance of a balanced diet that is rich in natural sources of folate, including spinach, orange juice, lentils and other beans, because those foods are healthy for all sorts of other reasons too.
For a chart on the amount of folic acid/folate in foods, go to ods.od.nih.gov/factsheets/folate.asp.