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Folic Acid Benefits, Side Effects & Safety Information

Published: 13th May 2018. Last updated: 21th July 2019.

Luna Smithton

Editor & Fact Checker


Folic acid, also known as vitamin B9, is a synthetic form of folate. Folate is a B-group vitamin which plays a vital role in many bodily functions, particularly the development of red blood cells and prevention of birth defects in infants. Since folic acid is a water-soluble vitamin, this means your body can't store it, and daily intake is necessary.

Like all B-group vitamins, folic acid plays a key role in maintaining a healthy nervous system and supporting your body’s ability to process carbohydrates and fats.

While many foods (such as legumes, fruits, and leafy greens) are naturally high in folate, folic acid doesn’t naturally occur in food. Therefore, it is often added to various supplements and refined grain products, such as cold cereals, pasta, bread, cookies, and crackers.

Since folic acid is different from its natural form folate, it must be converted into an active vitamin B9 (known as 5-MTHF) before your body can make use of it. How quickly this conversion takes place is affected by your genetics.

The conversion is a four-step process which requires a few different enzymes (including an enzyme called MTHFR). Genetic mutations can make some MTHFR enzymes less effective at converting it into 5-MTHF, which may lead to folic acid build-up in the blood. This has been linked to several health issues, including reduced brain function, and poor immunity. More research is needed on this – yet those with MTHFR mutations should avoid consuming folic acid in high quantities.

While you can get folate from many natural sources, research does show that many people don’t consume get enough folate through their diet [1].

Folic acid is used to treat other health problems associated with folate deficiency, such a liver disease, alcoholism, ulcerative colitis, and kidney dialysis. Women who are pregnant may also take folic acid to prevent miscarriage and neural tube defects.

The Potential Benefits of Folic Acid

Below we've listed every potential benefit that's got credible scientific backing:

It May Help Prevent Birth Defects

Some studies show that low levels of folate during the early pregnancy weeks could be linked to neural tube defects in infants (such as malformations of the spine, spinal cord, or the brain) [2]. Other studies show that children of women who do take folate supplements before and throughout pregnancy are born with much lower rates of these defects [3].

It is estimated that up to 90 percent of women don’t get enough folate through their diet for maximum protection against these defects. Therefore, women of reproductive age are recommended to take a supplement of folate (at least 400mcg) [4]. It is also recommended to look for a supplement that contains methylated folate – which is an active form of the vitamin which the body can use without needing to convert.

It May Help Prevent Cancer

Research suggests that high intakes of folic acid could prevent against certain types of cancer, including breast [5], pancreas [6], gut and lung. Scientists estimate that this is due to the role folate plays in controlling when genes are turned on and off. Some research even suggests that low levels of folate could increase your risk of cancer [7].

Other studies indicate that low levels of folate may also lead to the formation of easily breakable DNA, this way increasing the risk of cancer [8].

However, the research is conflicting – and there is some evidence that high folate intake may actually contribute to tumor growth in those who have pre-existing cancers [9]. There is also some evidence that suggests that folic acid supplements (i.e., not natural folate) may be associated with the occurrence of certain types of cancer [10].

More research in the field is needed to determine the impact supplemental folic acid may have on cancer risk.

It May Prevent Heart Disease

There is also evidence that folic acid reduces homocysteine levels. Homocysteine is an inflammatory molecule which has been linked to heart disease.

Folic acid uses homocysteine to convert it into a molecule called methionine, this way lowering its levels. This also means that folate deficiency could slow down this conversion – and levels of homocysteine could rise.

Some studies [11] show that daily supplementation of folic acid may reduce the levels of homocysteine by up to 25 percent. However, it appears that the reduction hasn't necessarily meant lower rates of heart disease. More research is needed to determine the reasons for that – but the results suggest that other significant factors influence heart disease.

It May Be Useful For Maintaining A Healthy Body Weight

All B-group vitamins are vital for maintaining good health, and for the body to use carbohydrates, fat, and protein for energy [12]. Therefore, it is important to ensure you get enough folate/ folic acid daily to maintain healthy metabolism and digestion.

However, there is some evidence that excess folic acid could contribute to weight gain, so you should make sure you check whether you need a supplement [13].

May Enhance Brain Function

Folate is an essential nutrient for healthy brain development and function.

Some research shows that low blood folate levels are linked with cognitive decline in the elderly, psychiatric, and epileptic people [14, 15].

Low levels of folate have also been linked to degeneration of the cerebral cortex (the region of the brain which coordinates memory and learning) [16].

Research conducted with animals with bacterial meningitis shows that higher folate intake prevented oxidative damage to the frontal cortex, and preserved memory function [17].

It May Help With Red Blood Production

One of the primary functions of folic acid is red blood replication and division.

Folate deficiency could cause megaloblastic anemia (a reversible condition characterized by fewer blood cells) [18].

It Can Support The Immune System

Research indicates that those with lower levels of folate are more susceptible to infection [19].

Megaloblastic anemia, a condition commonly caused by folate deficiency, results in a weakened immune system. However, supplementation with folate has been shown to restore the immune system in patients [20].

How To Use Folic Acid

The most common methods of taking Folic Acid are:

  • Capsules
  • Tablets

Because most people consume both folate and folic acid, intake requirements are also often described as “dietary folate equivalents” (DFEs):

  • 1 mcg (micrograms) of natural folate we get from food = 1 DFE
  • 1 mcg (micrograms) of synthetic folic acid taken with food = 1.7 DFE
  • 1 mcg (micrograms) of synthetic folic acid if taken on an empty stomach = 2 DFE

The RDI (reference daily intake) of folate is:

  • 400 mcg DFE for adults;
  • 600 mcg DFE for pregnant women;
  • 500 mcg DFE for breastfeeding women.

It is recommended that you don’t consume more than 1,000 mcg of folate/ folic acid daily.

Since folic acid is water-soluble, if you consume more of it than is needed, it will pass through your system when you urinate.

Which Foods Contain Folic Acid?

While folic acid isn’t naturally found in foods, many foods contain its natural form – folate.

The list of folate-rich foods include:

  • Leafy greens (e.g., spinach, arugula, and kale)
  • Other vegetables (e.g., beetroot, broccoli, avocado, asparagus, brussels sprouts)
  • Fruits (e.g., melons, bananas, papaya, oranges, and lemons)
  • Meat (e.g., liver, kidney)
  • Legumes (peas, beans, and lentils)
  • Eggs
  • Nuts and seeds

Foods that are fortified with folic acid include:

  • Pasta
  • Cereals
  • Bread, rolls, buns, and bagels
  • Flour mixes for bread
  • Rice, and other grain products

The Potential Side Effects of Folic Acid

While folic acid has many health benefits and is used to treat multiple health conditions, just like with any supplement, it could have some side effects.

The most common side effects associated with folic acid are:

  • Poor appetite
  • Nausea
  • Gas or bloating
  • Trouble sleeping
  • Funny taste in your mouth
  • Feeling overly excited, or depressed

According to WebMD [14], most people are unlikely to experience any side effects when taking doses lower than 1000mcg. However, higher doses could cause some severe side effects, such as:

  • Abdominal cramps
  • Diarrhea
  • Sleep disorders
  • Irritability
  • Confusion
  • Seizures
  • Skin reactions
  • Nausea
  • Behavior changes
  • Stomach upset

There are also concerns that taking high doses of folic acid over a long period could lead to an increased risk of heart attack in people with heart problems. Additionally, high doses of folic acid have been linked to increased lung or prostate cancer risk.

Note: these side effects are possible but may not be the typical user experience.


Folic acid is an important micronutrient which is part of the vitamin B group. It is primarily needed for the healthy production of new blood cells and keeping your red blood cells healthy.

While many foods naturally contain folate, research indicates that most people don’t get enough of it from their diet - and some may develop deficiencies. Folate deficiency may lead to folate deficiency-lead anemia. If you suspect that you may have a deficiency, you should consult your doctor.

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