Vitamin B9, more commonly known as folate, is found in a wide range of foods including vegetables (especially leafy greens), legumes, cereals, eggs and fruit. With the exception of beef liver, meat is generally low in folate. Many foods are also fortified with synthetic folate, i.e. folic acid.
Adequate folate intake is extremely important during periods of rapid growth such as pregnancy, infancy, and adolescence.
This MNT Knowledge Center feature is part of a collection of articles on the health benefits of popular vitamins and minerals. It provides an in-depth look at recommended intake of folate, its possible health benefits, foods high in folate and any potential health risks of consuming folate.
Contents of this article:
The Recommended Daily Allowance (RDA) of folate throughout life is as follows:
Folate or folic acid, is found in a wide range of foods including leafy green vegetables, cereals, meats and fruit.
- Birth to 6 months: 65 mcg
- Infants 7-12 months: 80 mcg
- Children 1-3 years: 150 mcg
- Children 4-8 years: 200 mcg
- Children 9-13 years: 300 mcg
- Children and adults 14 and older: 400 mcg
- During pregnancy: 600 mcg
- During lactation: 500 mcg
Folate requirements increase during pregnancy and breastfeeding in order to fuel rapid growth and prevent neural tube defects in the fetus.
The most common causes of folate deficiency include an inadequate diet, alcoholism, and an increased requirement due to growth or intestinal disorders causing malabsorption.
Folate supplements play an important role in ensuring adequate intake in vulnerable individuals and at times of greater need for folate, such as in pregnancy. Increasing intake of folate-rich foods is also important as such foods typically also provide an abundance of other beneficial nutrients that act synergistically to support good health.
The recommended intake of 600 mcg of folate per day during pregnancy may be difficult to achieve through diet alone, prompting The American College of Obstetricians and Gynecologists to recommend that most people take a prenatal vitamin supplement during pregnancy to ensure that they obtain adequate amounts of folic acid and other nutrients.
Indeed, anyone who may become pregnant is recommended to obtain 400 mcg per day of folic acid from dietary supplements and/or fortified foods; this is in addition to the folate present in a varied diet.
Possible health benefits of consuming folate
Decrease risk of birth defects
Adequate folate (or folic acid) intake is essential during pregnancy to protect against miscarriage and neural tube defects in the fetus. Recent research has also shown that a father's folate status before conception may be just as important. In a study from McGill University, paternal folate deficiency in mice was associated with a 30% higher number of various birth defects than in offspring with no paternal folate deficiencies.5
Lower risk of depression
Low folate status has been linked to an increased risk of depression and poor response to antidepressant treatment. Folate may help ward off depression by preventing an excess of homocysteine from forming in the body, which can block blood and other nutrients from reaching the brain. Excess homocysteine interferes with the production of the neurohormones serotonin, dopamine, and norepinephrine, which regulate mood, sleep and appetite.4
Folic acid supplementation has not been suggested as a treatment in itself for depression, but it may be helpful in improving response to antidepressants such as fluoxetine, especially in women.13
Maintaining a healthy heart
Folic acid (and vitamin B12) supplements have been found to lower levels of homocysteine. As elevated levels of homocysteine are associated with an increased risk of cardiovascular disease, some researchers had suggested that folic acid and B12 may, therefore, reduce the risk of cardiovascular disease.
However, research now indicates that such supplements do not decrease the risk of cardiovascular disease, although they appear to afford a degree of protection against stroke.
People with above-normal levels of homocysteine are 1.7 times more likely to develop heart disease and 2.5 times more likely to suffer a stroke. In a 2012 meta-analysis of 19 randomized controlled trials that included 47,921 participants, the data suggested that supplementation with a B-vitamin complex reduced the risk of stroke by 12%, although it had no significant effect on the risk of cardiovascular disease, myocardial infarction, coronary heart disease or cardiovascular death.6
Folate and cancer
Low levels of folate intake are associated with an increased risk of breast cancer in women, while several epidemiological studies have suggested an inverse association between folate status and the risk of colorectal, lung, pancreatic, esophageal, stomach, cervical, ovarian and other cancers.7,8
Although the mechanism of protection is currently unknown, researchers believe that folate's protective effects have something to do with its role in DNA and RNA production and the prevention of unwanted mutations. There is no evidence that folate supplementation provides the same anti-cancer benefits and, indeed, several studies have found an increased risk of cancer progression with high doses of folate supplementation.
Specifically, evidence from laboratory and animal studies indicates that high folate status promotes tumor progression in colorectal cancer, and possibly other cancers, although this depends on the timing of high folate intake.9,11
During early preadenoma stages of cancer, high folate intake is associated with a lower risk of colorectal cancer, whereas a high intake after preneoplastic lesions are established appears to promote cancer development and progression.9,10,12
Foods high in folate
The bioavailability (the body's ability to absorb, use and retain) of folate varies greatly among foods and is difficult to measure. There are 150 different forms of folate and losses of 50-90% can occur during cooking, storing or processing. The best sources of folate are green vegetables, legumes and liver.
Asparagus and lentils are packed full of folate and are foods with some of the highest folate content.
Some of the best natural food sources of folate include:14
- Asparagus, cooked, 1 cup: 243 mcg
- Beef liver, braised, 3 ounces: 215 mcg
- Black-eyed peas, boiled, ½ cup: 179 mcg
- Lentils, boiled, ½ cup: 179 mcg
- Broccoli, cooked, 1 cup: 168 mcg
- Beans, white, boiled, ½ cup: 132 mcg
- Spinach, cooked, ½ cup: 131 mcg
- Lettuce, romaine, shredded, 1 cup: 64 mcg
- Avocado, raw, ½ cup: 59 mcg
- Egg yolk, 1: 27 mcg
- Banana, 1: 24 mcg
- Mushrooms, Portabello, grilled, 1 cup: 23 mcg.
In 1998, the U.S. Food and Drug Administration (FDA) and the Canadian government began requiring manufacturers to add folic acid to certain foods, including enriched breads, cereals, flours, cornmeals, pastas, rice and other grain products.
The typical North American diet contains a large amount of these foods, making fortified products an important contributor to overall folic acid intake. Other countries that require fortification of certain foods with folic acid include Costa Rica, Chile and South Africa.
Potential health risks of consuming folate
High levels of intravenous folic acid intake may cause seizure, and high doses of supplemental folic acid have been associated with an increased risk of the progression of certain cancers. Dietary levels of folate have not, however, been associated with any adverse effects.
An intake of folate in doses above 1000 mcg for adults or 800 mcg for those aged 18 or under can conceal a deficiency of vitamin B12. Vitamin B12 deficiency can cause permanent nerve damage and paralysis.
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with a variety than to concentrate on individual nutrients as the key to good health.