What is vitamin B12?

Vitamin B12, also called cobalamin, is one of the 8 B-group vitamins. It’s one of the only water-soluble vitamins that can be stored by the body, which means the body can keep some aside for later!

Deficiencies and vitamin B12's roles in the body

Getting your required amount of vitamin B12 is essential, as this vitamin performs several tasks within the body.

Nervous system function

Vitamin B12 helps balance and protects the nervous system. In fact, it’s essential for preserving the myelin sheath, an envelope layer which protects neurons. This means that vitamin B12 deficiency can ultimately lead to severe neurological disorders such as loss of feeling, tingling, numbness, difficulty walking, memory problems and frequent mood swings.

Red blood cell synthesis

In combination with iron and vitamin B9, vitamin B12 plays a role in the production of red blood cells (erythrocytes) and therefore supports healthy blood formation. Its role is so significant that vitamin B12 deficiency can cause a specific form of anaemia called macrocytic anaemia (meaning “large cell” in Greek), where larger-than-normal red blood cells are produced, resulting in chronic fatigue.

Keeping body tissue healthy

Vitamin B12 plays a vital role in producing body tissue and keeping it healthy, because it’s involved in both DNA synthesis and cell division processes. A vitamin B12 deficiency could therefore be noticed as a change in the quality of hair, nails or skin and mucous membranes (redness, inflammation, psoriasis, eczema).

Energy metabolism

Vitamin B12 also plays a significant role in energy production. Like most B-group vitamins, it helps metabolise proteins, lipids and carbohydrates, regulating energy metabolism.

Cardiovascular health

Vitamin B12 contributes towards reducing cardiovascular risk. Together with vitamin B9, it helps keep homocysteine, an amino acid that’s toxic in large quantities, from accumulating in the blood. This accumulation can stimulate arterial plaque buildup, which is known to increase the risk of cardiovascular disease. Studies have also shown that taking a supplement of vitamin B12, combined with folic acid and vitamin B6, may help reduce the formation of lipid deposits in the arteries.

Populations at risk of deficiency and dietary supplements

Populations at risk of deficiency and dietary supplementsn

A vitamin B12 deficiency may result from a lack in nutritional intake – a diet that doesn’t meet the body’s needs. As vitamin B12 is only found in food from animals, people whose diets don’t include animal products, like vegetarians and vegans, are at high risk of vitamin B12 deficiency. Since potentially serious disorders can result from a vitamin B12 deficiency, a supplement is highly recommended for people with plant-based diets. Anyone following a vegan or vegetarian diet is therefore strongly advised to increase their vitamin B12 intake through dietary supplements or industrially fortified foods.

While less restrictive than veganism, the vegetarian diet may still be low in vitamin B12. For this reason, vegetarians are sometimes advised to take dietary supplements to prevent the risk of deficiency if they don’t have a balanced diet.

Vitamin B12 deficiencies and pregnancy

Vitamin B12 requirements increase during pregnancy. This is why getting a suitable amount of vitamin B12 while pregnant is vital for the good health of the mother as well as that of the developing foetus. Vitamin B12 deficiency during pregnancy may (as with vitamin B9 deficiency) lead to severe complications for the baby, such as the risk of miscarriage or neurological damage. It is, therefore, all the more important to be mindful of the risk of vitamin B12 deficiency in pregnant vegetarians or vegans.

Vitamin B12 deficiencies and the elderly

Elderly people are at double the risk for vitamin B12 deficiency. One reason for this is that, with age, the body has increasing difficulty absorbing sufficient amounts of micronutrients (such as vitamins, minerals and trace elements). Another reason is that age is often accompanied by changes in eating behaviour, particularly reduced nutritional intake or the exclusion of animal products, which can increase the risk of malnutrition and therefore vitamin B12 deficiencies.

Vitamine B12 deficiencies and malabsorption disorders during illness and/or medical treatment

In cases of chronic gastrointestinal illness, such as chronic gastritis, Biermer’s disease or Crohn’s disease, the absorption of vitamin B12 is heavily disrupted. For this reason, a vitamin B12 supplement is very often recommended to prevent any risk of deficiency. Similarly, anyone who has had partial surgical removal of the digestive system (stomach or intestine) will, in most cases, have to supplement their diet with vitamin B12 all throughout their life. Certain long-term medical treatments can also interfere with vitamin B12 absorption. This is true of gastric acid medications, contraceptive pills and oral antidiabetic drugs, for example. In the event of long-term treatment, it may be beneficial to take dietary supplements containing vitamin B12.

Daily vitamin B12 requirements

The European Union recommends a daily allowance (RDA) of 2.5µg of vitamin B12 for an adult. In France, since 2017, the dietary allowances recommended by ANSES (the French Agency for Food, Environmental and Occupational Health & Safety) have ranged from 0.8µg per day for young children to 4µg per day for adults.

Food sources of vitamin B12

In the natural world, vitamin B12 is synthesised by bacteria living in the soil or inside the digestive tracts of mammals and herbivores. It’s one of the only B-group vitamins that can be produced within our body, specifically through our intestinal microbiota.

However, most of the bacteria producing large amounts of vitamin B12 are found in the colon, located downstream of the ileum (the final section of the small intestine), which is where vitamin B12 is absorbed. Because of this, our bodies can’t synthesise and absorb an adequate amount of vitamin B12, so we need to get the rest of our recommended daily amount through our diet.

Vitamin B12 is different from other vitamins in that it’s only found in animal products and not in plant products. The best sources of vitamin B12 are therefore:

  • liver (75µg/100g) ;
  • offal (10µg/100g) ;
  • red meat (7µg/100g) ;
  • shellfish (15µg/100g) ;
  • mackerel (5µg/100g) ;
  • eggs (1,7µg) ;
  • dairy products (0,5µg/100g) .

Finally, certain algae (nori, chlorella) and cyanobacteria (spirulina) are occasionally presented as reliable dietary sources of vitamin B12. However, while they may contain the vitamin, studies have shown that the form of vitamin B12 found in these dietary sources is difficult for the human body to absorb, and it may even disrupt the vitamin B12 absorption process.

Side effects and contraindications of vitamin B12

Scientific literature reports no side effects linked to high amounts of vitamin B12 supplements, even in large doses, since any excess is filtered by the kidneys and removed through urine.

DID YOU KNOW? The origin story of vitamin B12

In the 19th century, the first studies on vitamin B12 emerged. The vitamin was identified while showing how administering liver extract could treat certain anaemias. It was then successfully isolated in 1948 thanks to the work of the American biochemist Karl Folkers.


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