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Folate (Vitamin B9)

Updated: Jan 22, 2021

What is Folate?

Folate is one of those vitamins better known by its name than its number (vitamin B9). This nutrient also has other names. It’s important to know the difference, especially if you have a deficiency or are debating starting a supplement.

Folate is the form of vitamin B9 that occurs naturally. The word is derived from the Latin folium, meaning leaf. This makes sense -- leafy greens are one of the best sources of folate that you can get from the diet!

5-methyltetrahydrofolate (5-MTHF) is the active form of folate. It is also known as levomefolic acid. During the digestive process, the majority of dietary folate is converted to this form before heading into the blood and onward to other body organs and cells.

Folic acid, also known as pteroylmonoglutamic acid, is a synthetic form of vitamin B9. It’s created for supplements, processed food products, and fortified foods such as flour, breakfast cereals, and nutritional yeasts.

Why I recommend Folate over Folic Acid

The majority of folate is absorbed and converted during the digestive process to a more bioavailable form of the vitamin (5-MTHF). Folic acid is unlike folate.

After consuming folic acid, not all of it is converted to the active form, 5-MTHF. Folic acid requires conversion through the liver or other tissues. For some people, this process can be slow and not as efficient as consuming a diet with naturally occurring folate.

If you are interested in supplementation, I recommend finding a third-party tested 5-MTHF vitamin to take. Especially for those with complex conditions, even small doses (200-400 mcg/day) might not be able to metabolize properly before the next dose.

Why intake of folic acid and fortified foods might not be getting the job done

As explained above, folic acid can take longer to metabolize than the naturally occurring folate we find in foods. This can be a problem because the folic acid competes for metabolism with the fortified foods or folate-high foods you are eating.

The result of this problem is that unmetabolized folic acid ends up in the bloodstream. High levels have been implicated in a range of health problems, and can be particularly dangerous for those with the methylenetetrahydrofolate reductase (MTHFR) gene mutation.

What does the body use folate for?

You’ve probably heard that folate is an important nutrient during pregnancy. This is true, but folate continues to be important throughout the life cycle as well.

Folate helps form genetic material (DNA and RNA) and assists in the process of protein metabolism. It also helps to break down homocysteine. Homocysteine is an amino acid that can cause harmful effects when it reaches high amounts in the body.

Measuring homocysteine levels in the blood can often tell us what the body’s folate status is. If levels are high, it is likely that folate absorption is impaired since folate helps metabolize homocysteine. When folate levels are low, homocysteine levels can be high because the breakdown process can’t continue without folate.

Recommended Amounts

Dietary Reference Intakes (DRIs)

The amount of folate recommended for daily intake depends on your age. Intake is based on the Adequate Intake (AI) level for those under one year old. This is the level assumed adequate to meet nutritional needs. An AI is established when there is not enough evidence for a Recommended Dietary Allowance, or RDA.

For children and adults, those one year and older, the recommended intake is based on the Recommended Dietary Allowance (RDA). This is the amount covering the needs of 97-98% of people in that specific age group or life stage (i.e. pregnancy).

Helpful terms to know

  • Recommended Dietary Allowance (RDA): covers the needs of 97-98% of individuals in a group; the average amount of a nutrient a healthy person should consume daily. Vary by gender, age, and whether a woman is pregnant or breastfeeding. Developed by the Food and Nutrition Board at the Institutes of Medicine (IOM) of the National Academies.

  • mcg = micrograms

  • Adequate Intake (AI): recommended daily intake of a nutrient; established by Institute of Medicine (IOM) to meet or to exceed the needed amount to maintain adequate nutrition for most people in a particular stage of life or gender group; established when not enough evidence is available to determine the RDA

  • Dietary Folate Equivalent (DFE): 1 mcg of food folate or 0.6 mcg of folic acid or 0.5 mcg supplement taken on an empty stomach


Who is at risk for a folate deficiency?

Folate deficiency is likely to occur in some particular populations.

The following populations/conditions may impair or increase the need for folate absorption:

  • Individuals with alcoholism

  • Non-hispanic black women

  • Pregnant women

  • Women of childbearing age

  • Those at high risk for breast or colon cancers

  • Genetic variations (i.e. MTHFR)

  • Surgeries involving the intestinal/digestive organs

  • Digestive disorders (i.e. Celiac disease, Inflammatory Bowel Disease)

  • Those taking certain medications (i.e. Methotrexate, Sulfasalazine, or antiepileptic or antiseizure medications

Signs & Symptoms

Common signs of a folate deficiency include:

  • Too few blood cells that are larger than normal (megaloblastic anemia)

  • Weakness

  • Fatigue

  • Irregular heartbeat

  • Shortness of breath

  • Difficulty concentration

  • Loss of hair

  • Pale skin

  • Sores in the mouth

Heart Disease & Stroke

High levels of homocysteine are linked with increases in risk of heart disease and stroke. Both folate and vitamin B12 are key to converting homocysteine into proteins that the body can use to build new and improved ones.

Without sufficient B vitamins, including folate, the conversion process gets backed up. The good news is that with rising levels of folate and other B vitamins, homocysteine levels drop.

A note of warning -- folic acid supplementation has not been associated with decreased risk of heart disease.

Neural Tube Defects

Too little folate can cause harm to the body, even in the earliest stages of conception. Low levels in pregnant women were linked with spina bifida, an abnormal development of the spinal cord and tissues surrounding it.

Folate During Pregnancy

The timing of intaking an adequate amount of folate during pregnancy is absolutely key. Many practitioners recommend women of a child-bearing age take a third-party tested multivitamin or even prenatal vitamin.

Folate is crucial to the development of a baby in the first few weeks following conception. In other words, a woman might not know she is low in folate or that she is pregnant -- yet her risk for having a baby with a neural (spinal) tube birth defect is increased.

Luckily, in 1998 the United States Food and Drug Administration (FDA) required that folic acid be added to most enriched breads. Now, you can find folic acid in many store bought breads, flours, cornmeal, pastas, rice, and other grain products. While I don’t recommend folic acid if you are looking for a high-quality supplement, it is nice to have a “safety net” built into our food stores.

Since the FDA mandate a few decades ago, neural tube defects have dropped by 28%. Studies show that fewer people have low levels of folate in their blood as well.


Another reason to get your folate from food first-- folate toxicity is extremely unlikely to occur from food sources alone. The Upper Limit is set for folate based on evidence that supplementing at a high level can mask a vitamin B12 deficiency.

Too little folate can be harmful, but too much folate or taking a form of folate that is not appropriate for your set of needs can also be dangerous for your health. The chart below can help you to safely navigate supplementation.

Helpful terms to know

  • Upper Limit (UL): also known as the Tolerable upper intake level; largest daily intake of a nutrient that is considered safe for most people; exceeding this limit is not recommended and may cause harm to the body; Set by the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine.

How To Determine Folate Levels

Folate status is usually diagnosed through a blood test. It is routine to check folate during a prenatal exam.

These tests should be run under direct medical supervision. Ask your doctor and dietitian for more information. Your vitamin status can be assessed through measurement of the following:

Due to some of the limitations of these tests, multiple exams and tests should be performed in order to establish a true deficiency. Home-testing kits are available, but I do not recommend them. They are often expensive and less accurate than the tests performed by a doctor or registered dietitian.

Sources of Folate

Although available in supplemental or synthetic forms, the best way to ingest folate is from whole foods.

The following foods have excellent levels of folate:

  • Asparagus

  • Avocados

  • Brussel sprouts

  • Leafy greens (i.e. spinach, lettuce)

  • Peas

  • Citrus

  • Fruits (i.e. bananas, melons)

  • Tomato juice

  • Eggs

  • Beans

  • Legumes

  • Mushrooms

  • Kidney

  • Liver meat

  • Poultry

  • Pork

  • Shellfish

  • Wheat bran

  • Fortified cereals and grains

How stable are folate and folic acid?

A relatively recent study on the shelf life of folic acid in corn masa flour offered some insight into the stability of folate. While there was not a significant loss in folate during the 6-month shelf life, there was a 13% loss with baking or frying.

Tortillas and chips baked or fried from the flour showed a significant loss with up to 17% percent decrease in folate over only 2 months on the shelf.

Biofortification and post harvest techniques are both being investigated as potential methods for improving folate availability from rice and other common crops.

Supplementation & Treatment with Folate

Uses & Treatment


Folate is an especially important vitamin during the gestation process. If you are pregnant or might become pregnant, discuss options for folate supplementation or food ideas with your healthcare providers.

It can be a good idea to find a dietitian to help you during this time. There are many dietitians like Lily Nichols RDN can help you understand folate during fertility and the pregnancy process. If you have a mutation of MTHFR, this extra focus on folate can be even more important and easier to understand with the help of a professional.


Supplementing with folate can be tricky when it comes to cancer. Folate has a key role in cell growth and creating DNA. Studies lead us to believe that folate can help suppress certain types of early cancer. However, research also shows that high doses of folic acid can exacerbate the cell growth of established cancers in the body.

The Bottom Line

Folate is an important vitamin, and one you should try to get from food first. If you may have cancer or are at risk, or if you are concerned about folate during pregnancy and fertility, contact your dietitian and doctor before starting a supplement regimen.


FREE Patient Resources & Products for Professionals

Notice something different? Free Patient Guides are often included in this section. I've decided to include the guide for folate in the Ask Anni article about MTHFR mutations and how to safely supplement. It's important to understand your options before supplementing which is why I've included the free guide for folate in the MTHFR article.


Related Posts



Arnarson A. Folic Acid vs. Folate -- What’s the Difference. Healthline. 2019.

Leo EK. Folate Deficiency. Healthline. 2020.

Office of Dietary Supplements. Folate (Fact Sheet for Professionals). National Institutes of Health. 2021.

Office of Dietary Supplements. Folate (Fact Sheet for Consumers). National Institutes of Health. 2021.

The Nutrition Source. Folate (Folic Acid) -- Vitamin B9. Harvard T.H. Chan School of Public Health. 2021.


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