Vitamin B12 (Cobalamin)

Here is a vitamin that is a real problem for vegetarian and especially vegans. It is not true that plant food can provide our body everything it needs. Vitamin B12 does not exist in the plant world and vegetarians who do not consume eggs or dairy products should really be concerned and assure their intake in B12.

Vitamin B12 along with vitamin B9 and B6, is needed for the conversion of homocysteine in methionine. Homocysteine is an amino acid, which, in excess, can be toxic to nerves and blood vessels.
When there is not enough vitamin B12, the homocysteine accumulates in the blood and high blood levels of this amino acids are responsible for injured vessels and could lead to heart attacks.

Moreover, the methionine seems to be needed for the production of myelin, the material that insulates our nerves. While the homocysteine build up in the blood, no methionine is formed and the nerve transmission is altered.

Vitamin B12 transforms one form of folic acid in another one, which is needed for the production of DNA and RNA. If there is a lack in vitamin B12, folic acid cannot be transformed and no DNA is produced. DNA is critical in the production of red blood cells. When there is a deficiency in B12 vitamin, red blood cells cannot divide. This problem is known as Megaloblastic anemia.


Ref: Recommended dietary allowances for the french population: CNRS-CNERMA


micrograms of vitamin B12 per day

Children 1-3 years


Children 4-6 years


Children 7-9 years


Children 10-12 years


Children 13-15 years


Teenagers (16-19 y)




Pregnant women


Nursing women


Deficiency symptoms
Our needs in this vitamin are very low and since it is stored in the liver, a deficiency in the vitamin can appear several years after one has stopped eating animal products.
Moreover, folic acid can mask a vitamin B12 deficiency. If the diet is rich in folic acid and low in B 12, anemia's symptoms will not develop and a person may not know that there is a problem until the more serious neurological symptoms appear.

Deficiency can result in nervous disorders and brain damage as well as a form of anemia: Pernicious anemia also called Megaloblastic anemia in which red blood cells are abnormally big.

Nervous damages can be permanent.

Who is at risk?

Good vegetarian sources
This vitamin is made from a bacteria.

Plant foods are completely devoid of B12 unless they are contaminated with bacteria. This can be the case when you organically grow your own vegetables and you do not wash them correctly. However, you cannot rely on our vegetables' dirt for your B12 intakes.

Many plant foods (tempeh, sea vegetables, spirulina, sprouted legumes, miso...) once thought to be good sources of B12 actually contain analogues. These are chemicals similar to vitamin B12 but have no vitamin activity for human. They also may interfere with vitamin B12 absorption.

100 ml of milk
mcg of vitamin B12
100 g of cheese
1 egg

Nutritional yeast can be a really good source of B12 vitamin only if the yeast has been grown on an enriched mold. Read the label or ask the supplier.

If the nutritional yeast you consume is not rich in B12 vitamin, you cannot really meet your needs in vitamin B12. You could eat 130 g of cheese per day and get your vitamin but you would also get too much saturated fats and cholesterol.
In that case it is better to rely on supplements.

Realized by Laurence LIVERNAIS-SAETTEL, Dietitian.
© Copyright L. Livernais-Saettel 2002
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