Shellfish in a pan

Can Vitamin B-12 help with anxiety?

Vitamin B12 is used by the body to help regulate the brain and nervous system. Given how vital this is to a healthy and well-functioning mind, could a B12 deficiency be a cause of anxiety?

What is it?

Vitamin B12, also known as cobalamin, is one of eight vitamins that form part of the B vitamins group.

To recap, a vitamin is something that the human body needs in small amounts to work properly. Typically we are unable to make them ourselves and so must obtain them from food.

The B family plays a key role in keeping the cells in your body healthy.

B12 specifically plays an important role in allowing the brain and nervous system to function correctly, as well as the formation of blood.

Where does it come from?

Humans cannot make B12. Nor can other animals, or even plants. The only things that can make it are bacteria.

How does it get in our body, then?

A process called bacterial symbiosis. Bacteria living inside some animals and plants produce it. And then we eat the animals and plants.

What if we don't get enough?

A lack of B12 can result in folate deficiency anaemia. This is a condition where the body produces abnormally large blood cells. These have low levels of haemoglobin, which is the stuff that carried oxygen around the body. So, it's really important.

Symptoms of a deficiency include:

  • Tiredness and lack of energy
  • Pins and needles
  • Mouth ulcers
  • Depression and confusion
  • Memory problems

How does it affect mental health?

Could a lack of B12 be a source of mental health problems? It certainly sounds plausible. Given its roll in regulating the brain and nervous system, it sounds like a prime candidate.

But what does the evidence say?

In 2007, McGill University published a paper reviewing the evidence1.

They noted there is decades of evidence showing that B12 deficiency correlated with mental health issues2. However, this is not proof in itself, as it could be that the effect that anxiety and depression have on our appetite leads to a diet that is poor in vitamins.

However, more recent evidence has suggested there may be a stronger link. A meta-analysis by Oxford University found that there was evidence that B12 supplements improved mental health3.

What remains unclear is whether it could help everyone, or whether it only helps people who are already folate deficient.

Not all studies agree. A 2003 meta-analysis by the Cochrane Collaboration looked at whether B12 could improve the mental health of people with dementia4. They concluded:

"From the three studies involving people with dementia or cognitive impairment and low blood levels of vitamin B12 eligible for inclusion in this review there was no statistically significant effect of vitamin B12 supplementation on cognition."

How might it work?

The evidence suggests B12 could improve our mental health. But how might it do this? Or, to use the technical term, what might be the mechanism of action (MOA)?

The research from McGill1 provides a possible explanation:

"In most, but not all, studies on patients with neuropsychiatric disorders, folate deficiency was associated with low levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). In one study, supplementation with folate restored CSF 5-HIAA levels to normal."

If B12 is vital to regulating our levels of serotonin, and serotonin is key to a healthy brain, this could provide an explanation.

What are good sources?

The best source of B12 is offal. 75g of lamb liver can contain as much as much as 60 mcg. Compare that to 18 mcg in 75g of mussels, 2.5 mcg in ground beef and 1.5 mcg in an egg.

Dietitians of Canada have put together an excellent table of good sources5.

Top tier:

  • Kidney
  • Liver
  • Shellfish

Also useful:

  • Cheese
  • Fish
  • Beef
  • Eggs

While those in the top tier will provide you with a much higher dose of B12, it is not that important. An adult only needs 2.4 mcg per day5. Therefore, only exceptionally poor diets will not achieve this.

Most of the time, a healthy and varied diet is all you need.

What if I am a vegan?

There is one exception to the "just eat healthy rule", and that is being a vegan. Because animals products provide almost our entire supply of B12, vegans can miss out.

The Vegan Society has put together a comprehensive guide on the subject. You can find it here.

They recommend:

Eat fortified foods two or three times a day to get at least three micrograms (mcg or µg) of B12 a day OR: Take one B12 supplement daily providing at least 10 micrograms OR: Take a weekly B12 supplement providing at least 2000 micrograms.

Should I take supplements?

You may already be taken them, in a way. Many products are "fortified" with additional vitamins, and this is the case in many countries for B12.

In the United States, Canada and Western Europe, most flour is fortified, for example. However, there are some notable exceptions. In many of the Nordic countries, fortification is restricted or simply banned altogether.

Therefore, it is likely that your diet provides all the B12 you need.

However, given it is safe to take additional B12 (see below for a discussion on higher dosages), you may want to try taking supplements to see if it improves your mood.

What are the side effects?

What happens if you take in too much B12?

Basically, nothing. Here is what the United States Institute for Medicine6 concluded:

"[there are] no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals"

So, even if you take supplements on top of a diet that provides all you need, you are unlikely to do yourself any damage. To be safe, always stay within the recommended dosage unless advised by your doctor.


Vitamin B12 is essential for keeping your brain and nervous system functioning correctly.

Studies have linked being deficient to a range of mental health problems, and the evidence suggests that taking supplements can improve these conditions.

It is likely that your diet already provides you will all the B12 that you need. In which case you are unlikely to see any benefit.

However, given taking supplements is safe and seems to have no adverse effects, you may wish to try it for yourself.

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Published 16 October 2017. Written by Chris Worfolk.

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  1. Young SN. Folate and depression--a neglected problem. J Psychiatry Neurosci. 2007 Mar;32(2):80-2. ↩︎

  2. Young SN, Ghadirian AM. Folic acid and psychopathology. Prog Neuropsychopharmacol Biol Psychiatry. 1989;13(6):841-63. ↩︎

  3. Matthew J. TaylorStuart M. CarneyGuy M. GoodwinJohn R. Geddes. Folate for Depressive Disorders: Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Psychopharmacology. Vol 18, Issue 2, pp. 251 - 256. DOI: 10.1177/0269881104042630 ↩︎

  4. Reem Malouf, Almudena Areosa Sastre. Vitamin B12 for cognition. Cochrane Dementia and Cognitive Improvement Group. 21 July 2003. DOI: 10.1002/14651858.CD004394 ↩︎

  5. Dietitians of Canada. Food Sources of Vitamin B12. 7 March 2017. Link. ↩︎

  6. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998. ↩︎