Harvard Medical School Commentaries: Food for Thought

May52011

Folic Acid -- Not Just for Pregnant Women

by Melissa Lumish, B.S.
Brigham and Women's Hospital

Folate is a water-soluble B vitamin that occurs naturally in food. Folic acid is the form of folate that used in supplements and added to some foods.

Folate is an important nutrient for pregnant women and women planning to become pregnant. Folate helps to reduce the risk of birth defects affecting the baby's brain and spinal cord. These are called neural tube defects.

However, folate has benefits for everyone because it:

  • Helps the body produce and maintain new cells
  • Is needed to make new red blood cells and helps prevent some types of anemia
  • May help protect against heart disease, some cancers and cognitive (mental) decline
  • Is related to fewer deaths from strokes

Americans tend to assume that if a little bit of something is good, then more must be better. However, there are risks to getting too much folate, whether you are a healthy adult or a woman who is pregnant.

Find out how much folate you need, how to avoid getting too much, and which foods are the best sources.

 

How Much Folate Do I Need?

The recommended dietary allowances (RDAs) for folate are based on age.

Age/Group

Micrograms

1-3 years

150

4-8 years

200

9-13 years

300

14-18 years

400

Adults (older than 19 years)

400

Pregnant women

600

Women who are breastfeeding

600

 

How Much Is Too Much?

Eating foods fortified with folic acid and taking supplements is a good way to get enough folate. There doesn't appear to be any harm to getting lots of folate naturally from foods. However, too much folic acid may be harmful to healthy adults and women who are pregnant.

Folic acid was added to the food supply in 1998. As a result, Americans increased their folic acid intake by more than 200 micrograms a day.

If you are pregnant:

Folic acid reduces the incidence of neural tube birth defects when taken during the first 8 weeks of pregnancy. But, many women do not know that they are pregnant until later than 8 weeks. That is why all women of reproductive age are advised to take 400 micrograms of folic acid a day, in addition to eating a balanced diet. Only 500 micrograms a day are needed to reduce the risk of neural tube defects.

Women in their second and third trimesters also benefit from folic acid supplements to help with increased cell growth. It takes just 450 micrograms of folate a day to maintain normal folate levels during the second trimester. This can come from a combination of dietary folate and folic acid.

If folic acid is so important during pregnancy, why not get as much as possible? Extra folic acid in your body during pregnancy may affect your baby after birth. Recent studies have suggested that too much folic acid during pregnancy could have some effects on your baby's health during childhood and into adulthood. The question of how much is too much is still being debated.

If you are a healthy adult:

The upper level of tolerance (UL) for folic acid is 1,000 micrograms a day for adults. This is because high folic acid levels with low vitamin B12 levels may lead to mental impairment.

Excess folic acid intake may also increase the risk of some cancers. For example:

  • Folic acid supplements have been linked to colorectal cancer and prostate cancer in people with undetectable pre-cancerous growths. But, there may be a lower risk of prostate cancer in men with higher folate intakes.
  • Women who take 400 micrograms or more of supplemental folic acid a day may have an increased risk of breast cancer compared with women who do not use supplements. However, folate intake is not related to breast cancer risk.

 

Food Sources of Folate

Folate is found in fruits, vegetables and many foods that are a good source of protein. It must be broken down in the gut before it can be absorbed.

Food

Micrograms

Meat and Protein

Beef liver (cooked, 3 oz, pan-fried)

221

Lentils (cooked, ½ cup)

179

Chickpeas (cooked, ½ cup)

141

Peanuts (dry roasted, 1 oz)

40

Eggs (1 large)

25

Vegetables

Asparagus (frozen, cooked, ½ cup)

122

Spinach (frozen, cooked, boiled, ½ cup)

115

Broccoli (cooked, ½ cup)

84

Green peas (frozen, boiled, ½ cup)

50

Artichokes (cooked, ½ cup)

43

Lettuce (Romaine, shredded, ½ cup)

40

Fruits

Avocado (1/2 cup sliced)

45

Orange (1 medium)

39

Tomato juice (6 oz)

35

Orange juice (6 oz)

35

Cantaloupe (¼ medium)

25

Papaya (1/2 cup cubes)

25

Banana (1 medium)

20

Sources: USDA Nutrient Database, release 18; NIH Dietary Supplement Fact Sheet, 2009

Many foods are fortified with folic acid. It was added to all enriched grain foods in 1998 to help reduce the incidence of neural tube defects. It is digested and absorbed more easily than folate. It takes only 0.6 micrograms of folic acid to equal 1 microgram of folate.

Food/Supplement

Micrograms

Fortified Foods

Breakfast cereals (fortified 100% DV, ¾ cup)

400

Breakfast cereals (fortified 25% DV, ¾ cup)

100

Rice (white, long-grain, enriched, cooked, ½ cup)

65

Egg noodles (cooked, enriched, ½ cup)

50

Bread (white or wheat, 1 slice)

25

Infant formula (Gerber Good Start, 5 fl oz)

15

Adult formulas (Ensure, Boost, 8 oz)

100-140

Supplements

Multivitamin

400

Prenatal vitamin

800-1,000

Folic acid

800

 

The Bottom Line -- Go Natural

Eat foods that are high in naturally-occurring folate. If you choose to take a folic acid-supplement, choose one that has no more than 400 micrograms a day unless your doctor advises you otherwise. Also, consider limiting your intake of foods fortified with 100% Daily Value (DV) of folic acid to avoid getting too much.

Although folic acid was added to our food supply to target reproductive-age women, Americans are getting an average of 200 micrograms a day through fortified foods. You can easily meet your needs with a balanced diet that has only naturally occurring folate.

Melissa Lumish is a dietetic intern at Brigham and Women's Hospital. She graduated with a B.S. in Human Biology, Health & Society and a concentration in dietetics from Cornell University.

Category: Food for Thought

Back to: Food for Thought