What we’ll cover.

  • What vitamin B12 is and types of B12
  • Benefit of B12 and its role in your body
  • Deficiency and illnesses
  • How B12 affects your brain
  • Absorption
  • Intrinsic Factor
  • Children, elderly and pregnant women
  • Amount of B12 needed
  • Fortified foods and supplements
  • Vitamin B12 foods and vegan options
  • Gut health relating to B12
 Reading time: 10 minutes

What is vitamin B12?

Vitamin B12 also known as Cobalamin is a water-soluble vitamin that’s found mainly in animal products like eggs, meat, dairy, fish and shellfish, however as vitamin B12 is created by soil based bacteria, there are some (very few) vegetarian and vegan options which we will touch on in this blog.

There are 4 main types of Cobalamins:  Methyl-, adenosyl-, cyano- and hydroxo-

Methyl-cobalamin and adenosyl-cobalamin are both cofactors, (think of cofactors as “helper molecules”) of vitamin B12.  These 2 are found naturally in food – they are the most bioavailable – broken down where your body can use them as they are.

Cyano-cobalamin contains a cyanide molecule and is found in B12 supplements as well as certain fortified foods.

Hydroxo-cobalamin is used in hospitals to treat cyanide poisoning.

What does vitamin B12 do?

  • Red blood cells – Vitamin B12 supports your cellular function and works with vitamin B9 (folate) to produce red blood cells. 

  • Energy – Vitamin B12 is great for your energy levels and endurance.  Red blood cells carry oxygen to your muscles and also transport carbon dioxide back to your lungs for you to exhale.  Muscles need oxygen – more blood cells means more oxygen.
  • DNA - Vitamin B12 is used in our body as a cofactor for DNA synthesis.

  • Mental health – Studies have shown that B12 deficiency is linked to many neurological disorders as well as stress and depression (1).

  • Sleep – Studies have also shown that vitamin B12 has a direct influence on melatonin (29) and it seems that it advances our sleep/wake cycle known as our circadian rhythm (30).

  • Thyroid – Vitamin B12 (31) and Iodine (32) deficiency are both linked to Hypothyroidism.

  • Nervous system – Vitamin B12 is the cofactor in Myelin formation.  Myelin is an insulating layer that forms around the nerves in your brain and spine, protects fibres and insulates neurons. 

    Myelin allows your nerves to work optimally and electrons to transmit quickly and efficiently.  A lack of vitamin b12 can cause neurological disorders like MS (Multiple Sclerosis) (33).

  • Reproductive system in men – Vitamin B12 increases semen quality and sperm count (34).

  • Immune function – Vitamin B12 is linked to increased cellular immunity.  B12 modifies immune response and the functioning of the immune system (35).

  • Serotonin and dopamine – Vitamin B12 is a cofactor for serotonin and dopamine synthesis.

Synthesis Snapshot

Synthesis happens in your body every second throughout your entire life.  It’s the process of creating an entity from 2 or more components.  

For example, your body takes the raw material called cholesterol and after several steps it gives you testosterone. 
These several steps are complicated, we won’t get into them; however it’s important to note that part of those several steps often involve vitamins, minerals, enzymes as well as other agents and without them synthesis is not possible or is hindered.  Why is this important?  

Let’s take an example – serotonin (our happy hormone) – it requires vitamin B12 and folate (2) – these are the cofactors (helper molecules).
If there’s a vitamin B12 or folate deficiency in the body, then 1 or 2 of these contributors that help create serotonin can become missing, hindering its synthesis. 
If serotonin is missing (same applies to dopamine), then happiness is missing – see how depression is linked to vitamin B12 deficiency?

Vitamin B12 and your brain

Elderly – B12 is great for the elderly.  The brain is an organ that behaves like a muscle but is approximately 60% fat and 75% water and has around 100 billion neurons. 
If we lose brain cells; we lose neurons as vitamin B12 helps the brain fight against Dementia and Alzheimer’s (3), this is because B12 helps protect us from brain atrophy (wasting away or shrinkage).  

Infants & children – Vitamin B12 is specifically important for the developing brain of infants and children during their first 2 years where brain growth is most rapid.  

Myelination (the process of forming the protective fatty layer around nerves) happens during this time too and may be vulnerable to B12 deficiency (4)

Symptoms from vitamin B12 deficiency may include agitation, irritability, negativism, confusion, disorientation, amnesia, impaired concentration and attention, sadness, brain fog and insomnia.

Psychiatric disorders that may form from having vitamin B12 deficiency include depression, bipolar disorder, panic disorder, psychosis, phobias and dementia (17).

Given that vitamin B12 is so heavily involved in the brain and nervous system, and given that neurological damage is often permanent, it makes sense to use vitamin B12 as a preventative.

Most important – vitamin B12 absorption

It’s one thing to get enough Vitamin B12, the other and more important thing is to absorb it, and this is the biggest obstacle. 
Unlike other vitamins, vitamin B12 requires that your digestive system and your liver are working efficiently. 
Vitamin B12 is absorbed in your intestines with the aid of intrinsic factor (IF), also known as gastric intrinsic factor (GIF).  It’s a glycoprotein produced in the parietal cells in your stomach.  

Intrinsic factor binds to B12 and carries it to the ileum which is located in your small intestines where the B12 gets absorbed into your bloodstream.
Gut health is extremely important in the creation of intrinsic factor and absorption of vitamin B12.

Why people don’t absorb enough vitamin B12

It’s assumed that we absorb 50% of dietary vitamin B12 (5) and it’s estimated that 2-3% of people only absorb around 1% of the B12 that’s available.  9% of people are B12 deficient and 40% are on the marginal low end (36).

Pernicious anemia is an autoimmune condition where anti-intrinsic factor are produced and these antibodies hinder the absorption of vitamin B12 (37).  This condition only affects 0.1% of the general population, but 1.9% of people over the age of 60 (38).

Malabsorption of vitamin B12 is most common in the elderly because as we age we produce less gastric acid which results in less intrinsic factor.  However, younger people aren’t in the clear.
Other causes of vitamin B12 deficiency may include prescription drugs, alcoholism (42), antibiotics, fish tapeworms (41), intestinal resection, tropical sprue, Crohn’s disease, Zollinger-Ellinger syndrome, bariatric surgery/gastric bypass (40), Imerslund-Grasbeck syndrome (20)

Proton pump inhibitors (PPIs) (39) and antacids are linked to vitamin B12 deficiency.  Antacids increase the pH level in your stomach which needs an acidic environment to digest and absorb optimally.

The lifestyle most people lead isn’t kind to their gut.  Fast food, alcohol, smoking, soft drinks (sodas), antibiotics and pesticide sprayed food – these aren’t the makings of great gut flora.

Think about it – you would never fuel your car with anything that was bad for it because it wouldn’t run well and would probably break down, and your car is important to you. 
Our body is exactly the same – the only difference is we break down slowly and painfully over time.

Mini summary – vitamin B12 full circle.

Vitamin B12 = red blood cell formation.  
B12 deficiency = less red blood cells = less oxygen carried to the brain, muscles, tissues and organs.  

The brain needs oxygen – brain cells die without oxygen – our brain controls the rest of us.  

Vitamin B12 = myelin synthesis.  Myelin protects the billions of neurons in our nervous system sending messages all over our body.

They’re all interlinked.  Oxygen, neurons, red blood cells – it’s no wonder vitamin B12 deficiency is linked to so many brain and neurological disorders.

What can you do to absorb more vitamin B12?

Gut health – Get into home-made kombucha tea, kefir, prebiotic foods and probiotics.  The importance of gut health cannot be stressed enough – it is the basis of good health and repair.

Chew – Chew your food well before you swallow.  Your saliva contains R-protein which protects vitamin B12 as R-protein doesn’t get broken down by gastric acid in your stomach. 
It makes its way to the duodenum; located at the beginning of your small intestines and it is there that pancreatic enzymes break down the R-protein which releases the vitamin B12 and that’s where the intrinsic factor binds to it and transports the B12 to the ileum for absorption.

Supplements and fortified foods.

Cyanocobalamin has a cyanide molecule and is a synthetic version of vitamin B12.  Our body takes cyano- and converts it into the bioavailable methyl- and adenysolcobalamin.
One of the reasons it’s used by pharmaceutical companies for supplements and food companies to fortify their food is because of how cheap it is to create.  

Not natural to our body, we only absorb 2% of what we ingest from B12 supplements or fortified foods that are of the cyanocobalamin type (6).  For this reason, we will be sticking to natural foods further down.

The ideal supplement for vegans or vegetarians would be a vitamin B12 supplement that contains methylcobalamin and adenosylcobalamin.  And ideally, a supplement that you can absorb under your tongue.
This type of supplement is both harder to find and a lot more expensive – but worth sourcing.

How much vitamin B12 per day?

B12 (mcg = micrograms)





0–6 months*

0.4 mcg



7–12 months*

0.5 mcg



1–3 years

0.9 mcg



4–8 years

1.2 mcg



9–13 years

1.8 mcg



14+ years

2.4 mcg

2.6 mcg

2.8  mcg

*Adequate Intake

Note:  Vitamin B12 is not toxic, meaning it doesn’t store in excess like some other vitamins or minerals.  Your body uses what it needs, it stores some in your liver, and excess B12 is secreted out of your body via urine.

Given that we might be absorbing 50% or less, the daily value that’s recommended is 6mcg and given that it’s non-toxic, you can take more than 6mcg.

Natural foods that contain vitamin b12:

Micrograms (mcg) of B12 Per 100g                                           
DV = Daily Value 
  • Mollusk & clams 98.9 mcg – 1648% DV (21)

  • Sardines 8.9 mcg – 149% DV (22)

  • Liver 
    Beef 83.1mcg - 1386% DV (23a) 
    Lamb 85.7 mcg – 1428% DV (23b). 
    Chicken 21.1 mcg – 352% DV. (23c)

    NOTE:  Liver contain massive amounts of Choline, Riboflavin and Folate which is great, but also massive amounts of Vitamin A and Selenium – both of these are needed in moderation.

  • 2 large eggs (116g) - 1.4 mcg – 26% DV (24).  Organic eggs are best.

  • Wild Trout (emphasis on wild) 6.3 mcg – 105% DV (25)

  • Wild Salmon 3 mcg – 51% DV (43). 

  • Yogurt (normal) – 0.4 mcg - .  Low fat – 0.6 mcg – 10% DV (27)

  • Beef (various cuts) – 11.5 mcg  - 192% DV (28)

Vegan options

(mcg = micrograms)

There’s a lot of conflict and opposition of views.  Some studies show that B12 is found in some of the following plant based foods while other studies and websites show that B12 isn’t found. 
One of the reasons this could be is because some foods have genuine vitamin B12 and some have B12 analogues – an inactive form of B12 which can be harmful (8),(8a).   
Some sites only focus on the one study without doing further research.

IMPORTANT: B12 Analogues or pseudovitamin B12 are molecules which have a similar chemical structure to genuine vitamin B12, but are NOT bioavailable and do not have the same function in our body. 
Analogue B12 are useless and also potentially harmful because they occupy the same intrinsic factor (transport mechanism) as the genuine B12. 
And because there's a limited number of intrinsic factor to transport vitamin B12, a number of genuine vitamin B12 may not be transported and therefore not absorbed – this is one of the reasons people are vitamin B12 deficient.

Best Choices of Plant Foods

Raw Nori (NOT dried nori) – Please read all of this.  There’s at least 54.5 mcg of B12 per 100g of dried purple laver (nori).  Around 4g of dried nori supplies the R.D.I of 2.4 mcg of vitamin B12.  However, dried nori has 35% genuine B12 and 65% analogue B12 (8a). 

Raw Nori has 73% genuine vitamin B12 and 27% analogue B12.   The equivalent weight for R.D.I of B12 in raw nori is 32g (13 sheets).  Nori is also very high in folate, iron, iodine and vitamin A.  

IF one’s gut health was optimal as well as their intrinsic factor production, one could consider dried nori. 
If their intrinsic factor supply was so abundant, that 35% genuine B12 and 65% analogue B12 could all be transported, then enough genuine B12 could possibly be absorbed regardless of analogue B12 taking up intrinsic factor as analogues are only really considered harmful because they hijack intrinsic factor. 
An analogy of this could be 35 genuine business people and 65 imposters want to go to a building and there are only 50 taxis - some genuine people could miss out. 
However, if there were 100 taxis, then all 35 genuine people could get to the building even though the other 65 imposters also got there. 
The 65 imposters get disregarded and the 35 genuine business people make it – now replace business people with B12. 

Shiitake Mushrooms
 – approximately 5.61 mcg/100 dried weight (9)[section 4.3].  Consuming 100g of dried shiitake mushrooms could provide the R.D.I of vitamin B12, however – note that in the study the results varied significantly and the average was 5.61 mcg of B12 per 100g. 
Other mushrooms are Black Trumpet (Craterellus cornucopioides) and Golden Chanterelle (Cantharellus cibarius) which contain 1.09-2.65 mcg/100g dried weight (12)

The NOT so best choices and myths

Why the mention?  Because too many websites have carelessly mentioned the below foods without actually going into the studies.

Tempeh – Range from 0.15-4.1mcg/100g with average of 1.9mcg/100g but these seem to be analogues (13) and in another article it specifically says vegans should not rely on tempeh as their source of vitamin B12 (13a)
Spirulina – Found to have great numbers of analogue/pseudovitamin B12 (14).  This is also valid for spirulina tablets where pseudovitamin B12 is predominant (15).  This is sad as spirulina is overall; amazing.

Miso – 0.12 mcg/100g (16).  100g of miso contains 3,728mg of sodium and barely hits 5% of your R.D.I of B12 and also is likely to be in analogue form.

Mushrooms with insignificant quantities of B12 (0.01-0.09 mcg/100g):
Porcini mushrooms (Boletus spp.) 
Parasol mushrooms (Macrolepiota procera) 
Oyster mushrooms (Pleurotus ostreatus) 

Below are other food items with no B12, analogue B12, or claims of B12 with no science to back it up, or sites who post non credible sources (i.e. their own article.) 
Dandelion, Alfalfa, Hops, Burdock Root, Chickweed, Catnip, Hawthorn Berries, Mullein Leaves, Red Clover Tops, Dong Quai, White Oak Bark.

Broccoli, asparagus, Japanese butterbur, mung bean sprouts, tassa jute, kimuchi, certain teas and water shield only have trace amounts of vitamin B12 and are not enough for the R.D.I in humans (19).


Getting high quality, genuine vitamin B12 from natural sources is the 2nd most important thing you can do.  The most important thing is to maintain your gut health – it’s the key to absorbing optimally. 
Vitamin B12 is by far one of the most important vitamins and crucial for your overall bodily function and mental health.
Make gut health your priority and consume foods naturally rich in vitamin B12 – your brain, DNA, cells and mood will thank you.

Written by Alan Khoshbakht

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