What is vitamin B12 (Cobalamin)?
Vitamin B12, also known as cobalamin, is one of the 8 B-group vitamins. It is one of the few water-soluble vitamins that can be stored by the body, allowing the body to maintain reserves!
This characteristic sets vitamin B12 apart from other B vitamins, highlighting its crucial role in maintaining neurological health, energy production, and red blood cell formation.
The body's ability to store vitamin B12, primarily in the liver, heart, and spleen, helps prevent short-term deficiencies and ensures a vital role in various metabolic processes.
Deficiencies and roles of vitamin B12 in the body
Meeting your vitamin B12 needs is essential as this vitamin supports numerous functions within the body, including energy metabolism, red blood cell formation, neurological health, and DNA synthesis.
Indeed, a vitamin B12 deficiency can lead to severe symptoms such as fatigue, neurological disorders, and megaloblastic anemia, highlighting the importance of a balanced diet or adequate supplementation to prevent these risks.
Nervous system function
Vitamin B12 contributes to the balance and protection of the nervous system. It is essential for maintaining the myelin sheath, a protective covering for neurons. Thus, a vitamin B12 deficiency can eventually lead to severe neurological disorders such as loss of sensation, tingling, numbness, difficulty walking, memory problems, or frequent mood changes.
Red blood cell synthesis
In combination with iron and vitamin B9, vitamin B12 contributes to the formation of red blood cells (erythrocytes) and therefore to optimal blood formation. A deficiency in vitamin B12 is also responsible for a specific type of anemia called macrocytic anemia (meaning "large cell" in Greek) because it results in the formation of red blood cells larger than normal, leading to chronic fatigue.
Tissue maintenance
Vitamin B12 plays an essential role in the formation and maintenance of tissues as it is involved in DNA synthesis and cell division processes. Thus, a vitamin B12 deficiency can manifest as poor skin quality and mucous membranes (redness, inflammation, psoriasis, eczema), hair, and nails.
Energy metabolism
Vitamin B12 also plays an important role in energy production, participating like most B-group vitamins in the metabolism of proteins, fats, and carbohydrates and therefore in the normal functioning of energy metabolism.
Cardiovascular health
Vitamin B12 helps to reduce cardiovascular risks because it helps to limit, along with vitamin B9, the accumulation of homocysteine, an amino acid present in the blood that is toxic in excess. Indeed, an accumulation of homocysteine in the blood promotes the formation of atheroma plaques, known to increase the risk of cardiovascular diseases. Studies have shown that vitamin B12 supplementation, combined with folic acid and vitamin B6, could help reduce the formation of lipid deposits on the arteries.
Populations at risk of deficiency and dietary supplements
Vitamin B12 deficiency and vegan diet
A vitamin B12 deficiency can result from a lack of dietary intake, meaning that the diet does not meet the body's needs. Since vitamin B12 is only found in animal-based foods, people who exclude animal products such as vegans are at high risk of deficiency. Therefore, due to the potentially severe disorders that can result from a vitamin B12 deficiency, supplementation is strongly recommended for those who have excluded animal products from their diet. It is thus highly advisable for people following a vegan or vegetarian diet to supplement with vitamin B12 through dietary supplements or industrially fortified foods.
Also, although less restrictive, the vegetarian diet can be low in vitamin B12. This is why it is sometimes recommended that vegetarians use dietary supplements if their diet is not balanced to prevent the risk of deficiency.
Vitamin B12 deficiency and pregnancy
The need for vitamin B12 increases during pregnancy. Therefore, during gestation, it is essential for all pregnant women to ensure they meet their vitamin B12 needs as it is essential for both maternal health and foetal development. A vitamin B12 deficiency during pregnancy can (like a vitamin B9 deficiency) lead to severe complications for the child, such as an increased risk of miscarriage or neurological damage. It is therefore crucial to monitor the risk of vitamin B12 deficiency in pregnant vegetarians or vegans.
Vitamin B12 deficiency and the elderly
Elderly people are at double risk of vitamin B12 deficiency. On one hand, as they age, their bodies have more difficulty absorbing sufficient quantities of micronutrients (vitamins, minerals, trace elements). On the other hand, age-related dietary changes, such as a decrease in food intake or exclusion of animal products, can promote the risk of malnutrition and therefore vitamin B12 deficiency.
Furthermore, certain pathological conditions more common in the elderly, such as atrophic gastritis or the use of acid-reducing medications, can interfere with vitamin B12 absorption, further increasing the risk of deficiency.
Vitamin B12 deficiency and malabsorption disorders in case of pathology and/or medical treatment
In the case of chronic gastrointestinal disease such as chronic gastritis, Biermer's disease, or Crohn's disease, vitamin B12 absorption is significantly disrupted. Therefore, vitamin B12 supplementation is often recommended to prevent any risk of deficiency. Similarly, people who have undergone partial digestive system removal (stomach or intestine) will most often need to supplement with vitamin B12 for the rest of their lives. Additionally, certain long-term medical treatments can affect vitamin B12 absorption. This is the case, for example, with medications for gastric acidity, contraceptive pills, or oral anti-diabetics. Therefore, in case of prolonged treatment, it may be useful to take vitamin B12 dietary supplements.
Daily requirements for vitamin B12
The European Union recommends a daily intake (RDI) of 2.5µg for an adult. In France, since 2017, the recommended intakes by ANSES (National Agency for Food, Environmental and Occupational Health Safety) range from 0.8 µg per day for young children to 4 µg per day for adults.
Dietary sources of vitamin B12
In nature, vitamin B12 is synthesised by bacteria living in the soil or in the digestive tracts of mammals and herbivores. Thus, it is one of the few B-group vitamins that can be produced by our body, especially by our gut microbiota.
However, most bacteria producing significant amounts of vitamin B12 are present in our colon, located downstream of the ileum (the terminal part of the small intestine), where vitamin B12 is absorbed. Thus, our body is not able to synthesise and absorb sufficient amounts of vitamin B12, so it must be obtained daily through diet.
Unlike other vitamins, vitamin B12 is unique in being found only in animal products and in no plant products. Therefore, the best sources of vitamin B12 are:
| Liver | 75µg/100g |
| Offal | 10µg/100g |
| Red meat | 7µg/100g |
| Shellfish | 15µg/100g |
| Mackerel | 5µg/100g |
| Eggs | 1.7µg/100g |
| Dairy products | 0.5µg/100g |
Finally, some algae (nori, chlorella) or cyanobacteria (spirulina) are sometimes presented as reliable dietary sources of vitamin B12. However, although they may contain it, studies have shown that the form of vitamin B12 found in these foods is difficult for the human body to absorb and may even disrupt vitamin B12 absorption.
The benefits and effects of vitamin B12
Vitamin B12 offers numerous benefits, particularly through its immediate effects on energy and mental well-being.
Crucial for energy metabolism, vitamin B12 directly helps to reduce feelings of fatigue and exhaustion, allowing individuals to feel an energy boost shortly after consumption.
Furthermore, vitamin B12 plays a significant role in red blood cell formation and nervous system function, helping to improve concentration and stabilise mood, which can be noticeable soon after starting vitamin B12 supplementation.
The side effects and contraindications of vitamin B12
Scientific literature reports no adverse effects associated with high vitamin B12 supplementation, even at very high doses, as excess is filtered by the kidneys and eliminated through urine.
EFSA (European Food Safety Authority) recommends a safe upper limit of 1000 µg (1 mg) per day for vitamin B12, a guideline that also applies to pregnant women, to prevent any potential complications without compromising health benefits.
No associations have been found between the intake of vitamin B12 naturally present in foods or as dietary supplements and risks of teratogenicity, adverse effects on fertility, postnatal development, or any carcinogenic or genotoxic properties.
Origin of vitamin B12
The first research on vitamin B12 began in the 19th century. It was identified by showing that administering liver extracts could correct certain anemias. It was successfully isolated in 1948 thanks to the work of an American biochemist: Karl Folkers.