Folate is a B vitamin (B9) that your body needs to build DNA, produce new cells, and process amino acids. It’s one of the nutrients your body cannot make on its own, so it has to come from food or supplements. The daily value for most adults is 400 micrograms (mcg), though pregnant and breastfeeding women need more.
What Folate Does in the Body
Folate’s most fundamental job is helping cells divide. Every time your body creates a new cell, it needs to copy its entire set of DNA, and folate is essential for building the molecular building blocks of that DNA. This is why folate matters most in tissues that turn over quickly: blood cells, the lining of your gut, and a developing embryo.
Beyond DNA, folate plays a role in converting the amino acid homocysteine into methionine, another amino acid your body uses for dozens of processes including gene regulation. When folate is low, homocysteine can build up in the blood, which has been linked to cardiovascular problems.
Folate vs. Folic Acid
These two terms are often used interchangeably, but they’re not identical. Folate is the form found naturally in food. It exists as larger molecules that your intestines must break down enzymatically before absorbing them. Folic acid is a synthetic version added to supplements and fortified foods. It’s simpler in structure and absorbs about twice as efficiently as natural food folate.
Neither form is biologically active right away. Both must be converted in the liver through a series of steps into the active form your cells actually use. This distinction matters especially for people with certain genetic variations (more on that below), because their bodies may struggle to complete that conversion efficiently.
Best Food Sources
Dark leafy greens, legumes, and organ meats are the richest natural sources. Here’s what a single serving delivers:
- Beef liver, braised (3 oz): 215 mcg, or 54% of the daily value
- Spinach, boiled (½ cup): 131 mcg (33%)
- Black-eyed peas, boiled (½ cup): 105 mcg (26%)
- Fortified breakfast cereal (1 serving): 100 mcg (25%)
- White rice, cooked (½ cup): 90 mcg (22%)
- Asparagus, boiled (4 spears): 89 mcg (22%)
- Brussels sprouts, boiled (½ cup): 78 mcg (20%)
In the United States, enriched grain products like bread, pasta, and cereal have been fortified with folic acid since 1998, at a level of 140 mcg per 100 grams of product. This adds an estimated 100 to 200 mcg per day to the diet of women of childbearing age. More than 50 countries now have similar mandatory fortification programs, including Canada, Chile, Costa Rica, and South Africa.
How Much You Need
The daily value for adults is 400 mcg of dietary folate equivalents (DFE). Pregnant women need 600 mcg DFE per day, and breastfeeding women need 500 mcg. The “dietary folate equivalent” unit accounts for the fact that folic acid from supplements and fortified foods is absorbed more efficiently than natural food folate. One mcg of folic acid taken on an empty stomach counts as 1.7 mcg DFE.
Why Folate Is Critical During Pregnancy
The neural tube, the structure that becomes the baby’s brain and spinal cord, forms and closes within just 28 days after conception. That’s before many women even know they’re pregnant. If folate levels are too low during this window, the neural tube may not close properly, leading to serious birth defects like spina bifida or anencephaly.
The evidence that folic acid prevents these defects is among the strongest in nutrition science. In landmark trials, periconceptional supplementation reduced the recurrence rate of neural tube defects from 5.9% down to 0.5%. The mechanism appears to involve folate’s role in DNA synthesis: developing nerve cells need a rapid, adequate supply of nucleotides to keep pace with the speed of neural tube closure. When folate is insufficient, cell division slows and the neural folds may not come together in time. There’s also evidence that folate supports proper gene methylation, a chemical process that regulates how genes are turned on and off, which is separately essential for normal neural tube closure.
This is why public health agencies recommend that all women who could become pregnant maintain adequate folate intake, and why grain fortification programs were created in the first place.
What Happens When You’re Deficient
Because folate is so central to cell division, the earliest sign of deficiency shows up in your blood. Red blood cells start coming out larger than normal, a condition called macrocytosis, which is often the first detectable change on a routine blood test. As deficiency deepens, these oversized cells can’t function properly, leading to megaloblastic anemia. In this type of anemia, the bone marrow produces large, immature red blood cells with a characteristic lacy nucleus that can’t carry oxygen as efficiently as normal cells.
Symptoms of folate deficiency anemia include fatigue, weakness, shortness of breath, irritability, and difficulty concentrating. Because the same type of anemia also occurs with vitamin B12 deficiency, distinguishing between the two requires checking blood levels of both vitamins.
The MTHFR Gene and Folate Processing
A gene called MTHFR controls a key step in activating folate inside your cells. A common variant of this gene, known as C677T, reduces the body’s ability to convert folic acid into its usable, active form. People who carry this variant may end up with higher levels of unprocessed folic acid circulating in their blood, along with elevated homocysteine.
This doesn’t mean everyone with an MTHFR variant develops problems. But it does explain why some people respond differently to folic acid supplements. For individuals with this genetic variation, supplements containing the already-active form of folate (sometimes labeled as methylfolate or 5-MTHF on supplement bottles) bypass the conversion step entirely.
Too Much Folic Acid: The B12 Masking Problem
Natural folate from food is not associated with any known risks at high intakes. Folic acid from supplements and fortified foods, however, carries a specific concern: it can mask a vitamin B12 deficiency. This has been documented since the 1950s. High doses of folic acid correct the blood abnormalities of B12 deficiency, making blood tests look normal, while the underlying neurological damage from low B12 continues silently in the background.
Some clinical evidence suggests that folic acid doesn’t just hide B12 deficiency but may actually accelerate the nerve damage it causes. The proposed mechanism involves folic acid triggering a burst of new blood cell production that depletes the body’s already-low B12 stores even further. This is one reason why B12 and folate levels are typically checked together, and why high-dose folic acid supplementation without checking B12 status can be risky, particularly in older adults who are more prone to B12 deficiency.