Both are vitamin B9. Both are widely recommended - particularly for pregnancy. They show up on supplement labels interchangeably and often without explanation.
They're not the same thing, and the difference matters in specific situations - especially if you have a common genetic variant that affects how your body handles one of them.
What Is Folate?
Folate is the form of vitamin B9 that occurs naturally in food. It's found in:
- Dark leafy greens (spinach, kale, romaine lettuce)
- Legumes (lentils, chickpeas, black beans)
- Asparagus
- Eggs
- Avocado
- Citrus fruit
"Folate" comes from the Latin word for leaf - folium - because leafy vegetables are among the richest sources.
In the body, folate is needed to make DNA and RNA, to support cell division (particularly critical during rapid growth, like in pregnancy), and to metabolise amino acids. It works closely with vitamin B12 - deficiency in either one can cause the same type of anaemia.
What Is Folic Acid?
Folic acid is the synthetic, oxidised form of vitamin B9 created for use in supplements and food fortification. It was developed in the 1940s and is more chemically stable than natural folate, which is why it's used in supplements and added to fortified foods (cereals, flour, bread in many countries).
Folic acid is not biologically active in this form. Before the body can use it, it needs to be converted to the active form - 5-methyltetrahydrofolate (5-MTHF), usually called methylfolate. This conversion happens primarily in the liver and gut.
Which Is Better Absorbed?
Folic acid actually has higher bioavailability than food folate - roughly 85% vs 50% for food folate when taken on an empty stomach. On this metric, folic acid supplements look efficient.
The complication is the conversion step. Folic acid must be converted to methylfolate before the body can use it. This conversion is handled by an enzyme called MTHFR (methylenetetrahydrofolate reductase). And roughly 40-60% of the population has a genetic variant that makes this enzyme less efficient.
The MTHFR Connection
MTHFR is a gene. A common variant in it (C677T, found in roughly 10-15% of people in a double copy, and another 40% in a single copy) reduces the activity of the MTHFR enzyme by 30-70%. This means:
- Folic acid isn't fully converted to the active methylfolate form
- Unconverted folic acid accumulates in the bloodstream
- High unmetabolised folic acid may mask B12 deficiency and has been associated in some research with impaired immune function (though this is still debated)
For people with MTHFR variants, taking methylfolate directly - the active, pre-converted form - bypasses the conversion problem entirely. It's available as "5-MTHF" or "methylfolate" on supplement labels, often slightly more expensive than standard folic acid.
This is worth knowing before pregnancy in particular. If standard folic acid supplementation isn't raising your folate levels adequately, MTHFR testing (a simple blood or saliva test) is worth considering.
Why Folate Matters So Much in Pregnancy
Adequate folate in the first weeks of pregnancy - often before a woman knows she's pregnant - dramatically reduces the risk of neural tube defects like spina bifida. The neural tube closes in the first 28 days of pregnancy. Getting folate right before conception and in early pregnancy is critical.
This is why folic acid fortification of flour was introduced in the US (1998), Canada, and Australia - and why women of childbearing age are widely advised to supplement.
The recommended dose during pregnancy is 400mcg/day as a minimum, rising to 5mg for women at higher risk (previous NTD pregnancy, taking anti-epileptic medications, BMI over 30, or known MTHFR variant).
Food Folate Still Matters
Supplements don't replace food-based folate. Whole foods provide folate alongside other B vitamins, minerals, and fibre that supplements don't replicate. Legumes and leafy greens are the most efficient dietary sources - and both are generally underconsumed in Western diets.
A 200g portion of cooked lentils provides about 360mcg of folate - close to the daily recommended intake from a single food. Dark leafy greens, asparagus, and chickpeas get you to meaningful amounts quickly when eaten regularly.
Which Should You Take?
For most healthy, non-pregnant adults without known MTHFR variants: standard folic acid or a food-first approach through legumes and leafy greens is sufficient.
For pregnancy: 400mcg folic acid daily from before conception, as per NHS/CDC guidelines. If you know you have an MTHFR variant, discuss methylfolate dosing with a GP or midwife.
For people who've had low folate levels despite supplementing: getting MTHFR tested is a practical next step. If you carry the C677T variant, switching to methylfolate is a reasonable change.