You might have heard about B12’s relationship with Folic Acid or Vitamin B9 and how the administration of B9 can make things worse for those who already have a vitamin B12 deficiency. Even if you haven’t  it’s time you learn about their relationship because B12 and B9 have a particularly close relationship (the extent of which might even surprise you!). If you already have some background knowledge about it, this article will definitely clarify the concept further.

Folic Acid (Folate)

Chemical structure of Folic Acid

Vitamin B12 and Folate Functions

Before going through the rest of this article, it’s better if you know about the functions of vitamin B12 – read more about it here.

Folic acid, on the other hand, is involved in the synthesis and repair of DNA. Therefore, it is required in large amounts when our cells are dividing rapidly in situations such as pregnancy, infancy and childhood. It is required for the formation of rapidly diving cells too, such as red blood cells. Along with B12, it also helps in the reduction of homocysteine levels, a chemical that has been long associated with an increased risk of heart disease.

At a biochemical level, Folate is required for the transfer of one-carbon units from donors such as serine,histidine and glycine to substances (known as intermediates) which are involved in the formation of amino acids, purines and thymine (which is a type of pyrimidine) – certain types of both of these groups participate in the formation of DNA.

Vitamin B12 & Folate: How Are They Related?

Vitamin B12 helps convert folic acid into a form that is usable by the body since we consume it in a form which is not biologically active. Without enough vitamin B12, we cannot effectively use the folate we take in. Therefore, those who have a B12 deficiency can also get deficient in folic acid even though their folate intake might be normal. Interestingly, the anemia can improve slightly when folate is given even if the person is not deficient in it and actually has a B12 deficiency.

That causes an improvement in the symptoms of anaemia making the patient believe he was suffering from folate deficiency. In this way, he will continue to stay deficient in B12 and his nervous system will undergo irreversible damage (since B12 is required to keep it healthy).

Simply said, anyone who is deficient in B12 will also get a functional deficiency of folic acid. The symptoms mostly overlap those of B12 deficiency so it doesn’t show up as a ‘separate’ deficiency. So even if you’re taking in enough folate, it won’t be used by your body in the absence of folic acid. In medicine, we refer to that as the ‘folate trap hypothesis’ because without vitamin B12, folic acid will end up getting trapped in your body. That’s one of the few aptly-named scientific phenomenon I have ever come across.

Staying true to my word, here’s the juicy and rather contradictory bit:


Woah – that sounds mightily absurd, doesn’t it? Let me tell you a story (I promise to keep it short, rest assured).

Once there was a time when many babies were found to have severely disabling and debilitating problems. These were called the ‘neural tube defects’ and included problems such as the spina bifida (where a baby’s vertebral column fails to fuse during foetal development) and parts of their spinal cord might protrude out through this defect. Obviously this might cause neurological problems depending on the degree of the defect (these problems can range from muscular weakness to complete paralysis and loss of normal bladder function).

I don’t want to scare you too much by going into the details of these defects, the point being that these neural tube defects could result in varying degrees of medical problems, even recurrent abortions or the birth of anencephalic babies (anencephaly literally means absence of the brain).

Luckily, the incidence of these defects has decreased massively – thanks to the discovery that the deficiency of folic acid before and during the first trimester of pregnancy causes these defects.Therefore, females planning to conceive as well as those who already are pregnant are now supposed to take an amount of folic acid higher than other people (for details, refer to the section of recommended daily intakes discussed below in this post).

To decrease the incidence of these defects, many food items of daily usage have been supplemented with folate (such as flour, bread, etc). Research has now shown that the administration of folic acid through these fortified foods to the general population might be one of the causes of the under-diagnosis of Vitamin B12 deficiency.

That’s because when people keep getting a constant supply of folate (when they are also B12 deficient), their anaemia gets partly cured. However, the damage to their nervous system continues to occur because they remain B12 deficient (since B12 is crucial in the normal functioning of the nervous system).

No, this does not mean that you shouldn’t take folate if you’re deficient in B12. It simply means that you need to take both when you’re deficient in B12. It also doesn’t mean that the general population should discontinue their usage of folate from the fear that they might have an undiagnosed B12 deficiency. If they discontinue folate intake, they will only make matters worse for themselves (along with increasing the incidence of neural tube defects, abortions, etc).

However, it does mean that doctors need to be way more vigilant when diagnosing people with megaloblastic anaemia (the type of anaemia that both folate and B12 deficiency cause). Both these vitamins go hand in hand and this should NEVER be forgotten.

Signs and Symptoms of a Folate & B12 Deficiency

The signs and symptoms of B12 deficiency have already been discussed here whereas those observed along with a folic acid deficiency are as follows.

  • Pallor
  • Tiredness
  • Fatigue
  • Light-headedness
  • Shortness of breathe
  • Heart palpitations
  • Peripheral neuropathy (which causes limb numbness, etc)
  • Pregnancy complications (such as neural tube defects in the foetus, miscarriages, etc).
  • Confusion, irritability and forgetfulness
  • A decrease in cognitive function
  • Sore or swollen tongue
  • Ulcers in the mouth
  • Heart disease (due to an increase in homocysteine levels).

Causes of B12 and Folate Deficiency

You can find the full causes of B12 deficiency in detail within our previous post. As a re-cap, it should be noted that B12 deficiency usually results due to inadequate B12 intake, gastric or intestinal surgery, diseases or tumors of the stomach or intestines, or parasites / toxins that compete for it. The causes of Folic acid deficiency are usually:

  • Reduced intake
  • Crohn’s disease, celiac disease and other causes of mal-absorption
  • Certain medicines, such as anti-epileptic drugs
  • Chronic dialysis
  • Haemolytic anaemia
  • Alcoholism and drug addiction

Daily Dosage and Sources of Folate

The RDI (Recommended Daily Intake) for folate is –

Age/Group RDI (in µg/day)
0-6 months 65
7-12 months 80
1-3 years 150
4-8 years 200
9-13 years 300
14-18 years 400
19+ 400
Pregnant women (age 14-18 years) 800
Pregnant women (age 19+ years) 1000
Lactating women (regardless of the age) 500

There are many sources of folate to be considered. You can find it especially in green leafy vegetables, Broccoli, Asparagus, legumes (Beans, peas and lentils), Avocado, brussel sprouts, sunflower seeds, egg yolks, liver, baker’s yeast and more.

Beef liver and a whole egg contain both B12 and folate. I recommend trying a combination such as salmon (high in B12) and a salad with leafy vegetables, legumes and beans (all are sources of folic acid) to form a meal that is very rich in both nutrients.

Alternatively, you can take vitamin supplementation tablets, etc which contain both B12 and folate, both of which are usually found in multi-vitamins, but always always opt for whole-nutrition before you surrender to artificial supplementation as a solution.

Written by Dr. Aqsa Ghazanfar, main author of ‘The B12 Deficiency Survival Handbook’.