Folic acid: what it does and why it matters in pregnancy

Folic acid is the vitamin your body uses to build new cells, and it matters most around pregnancy. Most people who eat a varied diet get enough of the natural form (folate) from food. But if you are trying for a baby or newly pregnant, the official UK advice is a daily 400 microgram folic acid supplement, because it lowers the risk of a birth defect of the spine. Here is what folic acid actually does, why timing is everything in early pregnancy, and how much you really need.

What is folic acid good for?

Folic acid (also called vitamin B9, and folate in its natural food form) works quietly in the background on jobs your body never stops doing. Three stand out.

• Cell division and growth. Folic acid is needed to make new cells and lay down DNA correctly. Anywhere your body is building cells quickly, it is involved. That is why it matters more during growth periods such as pregnancy.
• Making blood. Together with vitamin B12, folic acid helps produce healthy red blood cells, which carry oxygen around your body. When it runs short, this can go wrong and lead to a form of anaemia.
• The nervous system. Folic acid plays a part in the normal working of the nervous system and in how it forms. That is part of why it is so important in the first weeks of pregnancy, when a baby’s nervous system is being built.

So folic acid is not something you feel day to day. But if the building block is missing at a moment when your body is making a lot of new cells, that is exactly when it shows.

Folic acid and pregnancy: why it matters so much

Folic acid is best known around pregnancy, and for good reason. In the very first weeks, an unborn baby starts forming its nervous system. A key part of this is the neural tube: the structure the brain and spinal cord later develop from. If the body gets too little folic acid during that window, there is a greater chance the neural tube does not close properly. That is called a neural tube defect, and spina bifida (an open spine) is the best-known form. Getting enough folic acid at this stage measurably lowers that risk.

Here is the tricky bit: the neural tube closes very early, often before many women even know they are pregnant. So folic acid only does its job if you start in time. That is why the advice is to begin before you are pregnant, not once you find out.

The NHS advice is clear: take 400 micrograms of folic acid a day from the moment you start trying for a baby, ideally starting before conception and continuing until you are 12 weeks pregnant. If you have been trying for a while, or you are not sure where you stand, talk it through with your GP or midwife, as some people are advised a higher dose.

How much folic acid do you need?

How much you need depends on your situation.

• Adults in general. The UK reference intake for folate is around 200 micrograms a day. If you eat a varied diet with plenty of vegetables, pulses and wholegrains, you will usually get this from food alone.
• Pregnant or trying to conceive. Here the separate advice applies: a supplement of 400 micrograms of folic acid a day, on top of your normal diet. This is deliberately higher and comes from a supplement, because getting the right amount reliably from food alone, at the right time, is hard.

Worth knowing: the pregnancy advice is one of the few cases where the starting point is a supplement rather than food. That is because timing and certainty matter so much here. At other times in life, a folic acid supplement is not needed for most people.

Folic acid or folate: what is the difference?

You will see two words that seem to mean the same thing, which is confusing. Folate is the natural form found in food, such as green vegetables and pulses. Folic acid is the manufactured form used in supplements and fortified products.

Oddly enough, the manufactured form is absorbed slightly more reliably and steadily than natural folate from food. Folate from vegetables is fragile: some is lost during cooking and long storage. That is exactly why the pregnancy advice deliberately points to a folic acid supplement, rather than simply telling people to eat more spinach. For everyday life the distinction barely matters, as a varied diet gives you enough through folate. It only becomes important around pregnancy, when you want to be sure.

A folic acid deficiency: what would you notice?

A true folic acid deficiency is not that common in healthy people in the UK, but it can happen, for example with a very one-sided diet, with certain gut conditions, or with heavy alcohol use. Because folic acid is needed to make blood, a shortage mostly shows up in your red blood cells. Possible signs include:

• Ongoing tiredness and low energy
• Paleness and breathlessness (from anaemia)
• A sore, red or tender tongue
• Irritability or a low mood

These symptoms fit many causes and look a lot like a vitamin B12 deficiency. In fact, folic acid and B12 work so closely together that one can partly mask a shortage of the other. That is why dosing yourself high is unwise: you can paper over a B12 deficiency while the real cause carries on. Suspect a deficiency? Get it checked with a blood test through your GP rather than dosing on a hunch.

Which foods contain folic acid?

The natural form, folate, is spread across quite a few everyday foods. Good sources include:

• Green leafy vegetables such as spinach, kale and broccoli
• Pulses such as lentils, chickpeas and beans
• Wholegrain foods such as wholemeal bread and brown rice
• Some fruit, such as oranges
• Eggs and nuts

One thing to watch: folate is sensitive to heat and water. With long boiling, some leaches into the cooking water or breaks down. To keep as much as possible, cook vegetables briefly and with little water, for example steaming or a quick stir-fry. With a varied diet that includes daily vegetables and regular pulses and wholegrains, you are fine for normal everyday life. Pregnancy is the deliberate exception, because food alone does not guarantee the right amount at the right moment.

Who needs a folic acid supplement?

For most people who eat a varied diet, a standalone folic acid supplement is not needed. There are groups for whom it is sensible, or even advised:

• Women who are pregnant or trying to conceive. The clear advice is 400 micrograms a day, ideally from before conception until 12 weeks.
• People with reduced absorption. With certain gut conditions, or after stomach or bowel surgery, absorption can fall short. It is wise to check with your doctor here.
• Certain medications. Some medicines can affect your folic acid. If you take long-term medication, ask your GP whether this applies to you.

If you are not in a risk group and you eat a varied diet, a separate folic acid supplement probably adds little. A cheap own-brand tablet costs only a pound or two, so cost is rarely the issue, but for most people it is simply not necessary.

Dose and upper limit: can you get too much?

Folic acid is water-soluble, so you mostly pass out any excess. Even so, an upper limit has been set for the manufactured form: for adults, roughly 1,000 micrograms (1 milligram) a day from supplements and fortified foods combined. Folate from ordinary food does not count towards this, as you cannot realistically overdo it through eating.

Why a limit if you pass it out? A large excess of folic acid can hide a vitamin B12 deficiency. It fixes part of the anaemia caused by low B12, while damage to the nervous system quietly continues, so the B12 shortage gets spotted later. That is the reason not to sit on a high dose for no reason. The practical line: the pregnancy dose of 400 micrograms is well under that limit and is safe. If you have no specific reason to take more, stick to the recommended amount and skip the mega-doses. Unsure about your situation, especially around pregnancy or with medication? Talk to your GP or midwife.