What is cyano-cobalamin or vitamin B12?

Written by Catherine Saxelby on Wednesday, 07 January 2015.
Tagged: healthy eating, metabolism, vitamins

What is cyano-cobalamin or vitamin B12?
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Vitamin B12 (cyano-cobalamin) plays a vital role in metabolising food, manufacturing red blood cells, transporting and storing folate (a related B vitamin) and maintaining a healthy nervous system. 

 A substance called "intrinsic factor", is secreted by the stomach, enabling us to absorb the vitamin B12 in our food. People can be B12-deficient, even though their diet has plenty, because of stomach problems or a lack of intrinsic factor. In such cases, regular injections of B12 once a year can correct the deficiency which would otherwise lead to a serious type of anaemia called pernicious, or megaloblastic anaemia, fatigue and blood problems.

What does vitamin B12 do in the body?

B12 is essential for the synthesis of our DNA, our genetic material (and ultimately cell division) and for maintaining the integrity of the myelin sheath surrounding our nerves.

How much vitamin B12 do I need?

The Recommended Dietary Intakes (RDIs) for vitamin B12 per day are:


0.4 mcg for babies (0 to 6 months) AI*

0.5 mcg for babies (7 to 12 months) AI*


0.9 mcg for children (1 to 3 years)

1.2 mcg for children (4 to 8 years)

1.8 mcg for children (9 to 13 years)

Older children

2.4 mcg for children (14 to 18 years)


2.4 mcg for women (19 to 70+ years)

2.6 mcg for pregnant women

2.8 mcg for breastfeeding women.


2.4 mcg for men (19 to 70+ years)

(NRVs from NHMRC Australia 2006):

Note mcg = micrograms

*AI means Adequate Intake (used when this is not sufficient information to set as RDI)

Safe upper limit for vitamin B12

Vitamin B12 is safe and non-toxic even at large doses. No adverse effects have been associated with excess vitamin B12 intake from food or supplements in healthy individuals.

List of best vitamin B12-rich food sources

The best foods for vitamin B12 are almost exclusively animal foods such as meats, fish, seafood, poultry, eggs, cheese and milk. Vegans can run short (although only after a couple of years) and so require vitamin B12-fortified foods e.g. soy milk, yeast spread, vegetarian sausages or rissoles, to top up. Alternatively they can take a B12 supplement. More later.

My Top 20 food sources of B12

Here are the 20 richest foods for B12 listed by concentration by weight per 100g/3oz in descending order:

B12 Oysters smll

  1. Green mussels
  2. Chicken liver
  3. Oyster meat, fresh
  4. Sardines, canned & drained
  5. Yeast spread e.g. Vegemite, Marmite
  6. Rabbit flesh
  7. Duck egg
  8. Yelloweye mullet
  9. Beef mince, lean
  10. Veal or lamb, lean
  11. Red salmon, canned & drained
  12. Beef steak, lean
  13. Snapper
  14. Kangaroo
  15. Crab flesh
  16. Venison mince
  17. Turkey, hindquarter
  18. Chicken egg
  19. Beef sausage, lean
  20. Bream
    Source: NUTTAB from FSANZ

Vitamin B12 is produced by bacteria in the large intestines of animals, including humans, if the gut bacteria (biome or biota) are present in the right concentrations and types.

Plant foods (legumes, grains, nuts, vegetables) are generally not a source of vitamin B12 at all. So B12 is a nutrient of concern for vegetarians and particularly for vegans who choose an entirely plant-based diet.

Vegetarians who eat eggs and dairy (cheese, yoghurt, milk) are fine as they can obtain adequate amounts.

Easy ways get your recommended day’s intake of 2.4 mcg

Food combos Total B12 (mcg)
1 small green mussel at approx. 23g meat per mussel, steamed or boiled in broth 4.6
20g canned sardines (approx 1 fillet) 2.8
2 fresh oysters, at approx. 12g meat per oyster, dowsed in lemon juice and pepper 3.8
70g dry-fried beef mince in tomato pasta sauce 2.5
50g reduced-fat cheddar cheese on 100g boiled pasta 2.5
1 large glass (270mL) soy milk, fortified with vitamin B12 2.5
2 hard-boiled eggs on a wholemeal bread roll 2.4
1  piece of wholemeal toast,  spread thinly with yeast extract ~ 8g and 250ml glass of milk 2.4
80g barbecued snapper served with salad 2.4

Vitamin B12 deficiency signs

Most cases of vitamin B12 deficiency result from an inability to absorb the vitamin due to loss of intrinsic factor in the stomach (which is needed for B12 absorption), loss of gastric acid or protein-digesting enzymes.

There are many well documented factors that can cause this malabsorption, such as gastric resection surgery including stomach banding, gastritis, and the use of medications that suppress acid secretion in the stomach.

Vitamin B12 deficiency can lead to demyelinisation of the nerves, spinal cord and the brain, resulting in nerve damage and neuro-psychiatric abnormalities.

Neurological signs of vitamin B12 deficiency include:

  • numbness and tingling of the hands and feet
  • decreased sensation
  • difficulties walking
  • loss of bowel and bladder control
  • memory loss
  • dementia
  • depression
  • general weakness
  • psychosis.

Vitamin B12 deficiency ultimately results in megaloblastic anaemia and inhibition of cell division. However it has several stages and may be present even if a person does not have anaemia.

During pregnancy

Pregnant and lactating vegan or vegetarian women should ensure an adequate intake of vitamin B12 to provide for their developing baby.

An infant born to a vegan mother is at high risk of deficiency if the mother’s vitamin B12 intake is inadequate AND her stores in the liver are low. 

In infants, visible signs of vitamin B12 deficiency may include involuntary motor movements, dystrophy, weakness, muscle wasting, loss of tendon reflexes, psychomotor regression, shrinking and loss of growth in the brain and blood disorders.

Vitamin B12 facts

1. B12 and mushrooms has been an on-again, off-again debate over the years but ground-breaking research at the University of Western Sydney in 2009 revealed that there is a modest amount of B12 in mushrooms. They found that one serve of mushrooms (100g or three button mushrooms) has almost 5 per cent of the daily needs vitamin B12. What’s more the vitamin B12 occurs in the active form and not as pseudovitamin B12 which is inactive in humans. So, if the mushrooms are farm-cultivated, they do add a modest quantity of vitamin B12, which is often difficult for strict vegetarians to obtain and it is the same type of bio-available B12 as found in meats and seafood (meaning that it can be used by the body). 

2. Apart from mushrooms, vitamin B12 is only found in foods of animal origin - meat, fish, seafood, chicken, eggs, milk, yoghurt and cheese. That's why Vegans have a hard time getting enough of this vitamin. Generally it isn't a problem except in pregnancy and early childhood - when demand is high - because the liver has enough B12 stored away to last for up to five years. As insurance, however, if you're a vegan, it's wise to take a B12 supplement or eat some food that's B12-fortified such as some of the soy milks e.g. So-Good or soy sausages. Check the label.

Small amounts (say from B12-fortified milk or cultivated mushrooms) and frequent daily doses appear to be more effective than infrequent large doses, such intramuscular injections. 

3. Claims have been made that plant sources like seaweed or algae or fermented food such as tempeh contain vitamin B12. Usually this is a form of the vitamin that's inactive or unable to be absorbed by our bodies known as pseudovitamin B12. Some of the fermented vegetables may also have low levels of B12 from the wild bacteria or yeasts that grow on them. Unless you can see good proof, treat these claims with caution.






Catherine Saxelby About the author

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Catherine Saxelby has the answers! She is an accredited nutritionist, blogger and award-winning author. Her award-winning book My Nutritionary will help you cut through the jargon. Do you know your MCTs from your LCTs? How about sterols from stanols? What’s the difference between glucose and dextrose? Or probiotics and prebiotics? What additive is number 330? How safe is acesulfame K? If you find yourself confused by food labels, grab your copy of Catherine Saxelby’s comprehensive guide My Nutritionary NOW!