How much folate do you need per day?

The RDA for folate is 400 mcg DFE a day for adults and 600 mcg DFE in pregnancy.

These are the reference amounts used on US food labels and in dietary guidance, not personal targets. What you need shifts with age, pregnancy, medication and health conditions. The % Daily Value shown on every food page here is calculated against the FDA Daily Value for folate, which is 400 µg a day.

What this means for you

Four hundred micrograms a day for adults, 600 in pregnancy. For one group this is not a general nutrition target at all. It is one of the very few supplement recommendations in nutrition with randomised trial evidence standing behind it.

Established. If you could become pregnant, enough folic acid around the time of conception prevents a substantial share of neural tube defects. Those form in the first weeks, often before a pregnancy is confirmed, and that timing is the whole point. Starting once you know is too late for the thing it prevents. The advice is 400 micrograms a day from supplements or fortified food for anyone who might become pregnant, not only for people trying. After the United States made fortification mandatory in 1998, neural tube defect rates fell by 28 per cent.

For everyone else, food does the job

A cup of prepared edamame is 482 µg, which covers the day. A cup of cooked lentils is 358 µg. Leafy greens, asparagus, avocado and enriched grains fill in the rest. The word folate comes from foliage, and the etymology is a decent map of where to look.

One technical point explains the strange units. Folic acid, the synthetic form in supplements and fortified flour, is absorbed far better than the folate that occurs in food, at least 85 per cent against roughly 50. That is why doses are written in "dietary folate equivalents". It is also why the upper limit of 1,000 micrograms applies only to the synthetic form. No limit was set for folate from food, because high intakes from food have never been shown to cause harm.

The formula is worth seeing, because it is a convention rather than a measurement of your gut. Micrograms of dietary folate equivalents equal the micrograms of folate in food plus 1.7 times the micrograms of folic acid, a factor the Institute of Medicine set in 1998 and FDA adopted for the label. Everything on the packet rests on the assumption inside that 1.7: that folate from food is worth a good deal less than folic acid from a pill.

Unsettled. That assumption has been measured and it did not land where the formula puts it. Seventy-two healthy adults ate a controlled diet for four weeks. Folate from fruit, vegetables and liver came out at about 78 per cent of folic acid measured with labelled folate, and 85 per cent measured by the rise in serum folate. The 1.7 factor implies roughly 59. The intervals are very wide, 48 to 108 per cent, and they include 100, so this does not show that food folate equals folic acid. What it does show is that the label's factor is not securely below the data, and the authors say plainly that eating folate-rich food raises a population's folate status more efficiently than is generally assumed.

There is a second reason no single factor can be right. Twenty-four adults were given the same tracer dose of folate from spinach, wheat germ and Camembert. It reached the blood best and fastest from the spinach, and the variation between people was very high for the wheat germ. How much folate you get depends on the food it is sitting in, and one conversion number will not fit all of them.

Would more than 400 micrograms be better?

This is the obvious next question, and the honest answer is that it is still open. Two results from the last few years both bear on it and neither settles it.

Unsettled. Three trials gave women who were trying to conceive 4 to 5 mg of folic acid a day instead of the standard 0.4 mg. Among the 1,488 who became pregnant, the high dose went with about a quarter fewer miscarriages and a 10 per cent better chance of conceiving in the first place. Then the same data were counted a second way, including everyone who had been randomised rather than only the women who conceived, and the miscarriage effect shrank and stopped being significant. Three trials, low to moderate certainty, and a finding that changes shape depending on how it is counted.

The other result runs the opposite way. In women carrying twins who were given 4 to 5 mg a day from early pregnancy, pre-eclampsia turned up in 17.2 per cent against 9.9 per cent on placebo. Adjusting for the other differences between the groups pulled that below the line where it counts as a real difference, and the authors say plainly that the raised risk cannot be confirmed. Nobody should read it as proof of harm. Nobody should read it as permission either.

So 400 micrograms stands where it was. It is the dose the prevention evidence was built on, and the case for multiplying it by ten has not been made.

Not for everyone. If a doctor has already put you on 4 or 5 mg, none of the above is about you. There are real reasons to prescribe a high dose, and the person who prescribed it can see things about you that a website cannot. Take this page to them rather than to the bathroom cabinet.

Not for everyone. Large amounts of folic acid can correct the anaemia of vitamin B12 deficiency while the nerve damage underneath carries on. The blood test looks better while the person gets worse. This mostly concerns older adults, who are both more likely to be low in B12 and more likely to be taking supplements. It is an argument for checking B12, not an argument against folate.

The number behind that advice is worth stating plainly. Pooling ten systematic reviews covering 296,816 women, folic acid or a multivitamin before conception gave a pooled effect of 0.43 on neural tube defects, and folic acid on its own 0.23. The reviews built from randomised trials and the reviews built from cohorts agreed, which is rare enough to be worth noticing. On the claims about the child's brain, 39 observational studies point the same way and taking more than the recommended dose added nothing. the full review is here.

What running low actually looks like is worth knowing, because it is easy to mistake for something else. The main sign is megaloblastic anaemia, where red blood cells are large and abnormal, with weakness, fatigue, poor concentration, irritability, headache, palpitations and breathlessness. A sore tongue, shallow mouth ulcers and changes in skin, hair or nail colour come with it.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Foods highest in folate on this site

• Cornmeal, degermed, white fortified — 526 µg per 1 cup (131% DV)
• Cornmeal, degermed, yellow fortified — 526 µg per 1 cup (131% DV)
• Chicken, liver, all classes, cooked — 491.3 µg per 3 oz (123% DV)
• Edamame, frozen, prepared — 482.1 µg per 1 cup (121% DV)
• Lentils, mature seeds, cooked, boiled — 358.4 µg per 1 cup (90% DV)

All folate sources ranked →

Full guide: Folate and folic acid: the clearest success in nutrition policy, and its one side effect