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Vitamin B12 is probably one of the most discussed vitamins, likely due to its unique effects on pregnancy development and the health of the circulatory system. However, that's not all you need to know about this amazing vitamin. Read the article and learn more!
Vitamin B12 in chemical terms
Vitamin B12 , or cobalamin, is a water-soluble vitamin. Its name refers to a group of compounds called corrinoids, which have the biological activity of vitamin B12. These compounds have a cobalt atom (Co) in the central part of the corrin ring. Its structure is similar to the heme found in hemoglobin, particularly the porphyrin ring and the iron it contains. Vitamin B12, along with folic acid, is involved in the hematopoietic process/erythropoiesis—the production of red blood cells from the bone marrow. It is also involved in the biosynthesis of nucleic acids (DNA), cholesterol, and carbohydrates. It is also involved in the breakdown of the ketogenic amino acid isoleucine. Proper levels of vitamin B12 determine optimal levels of homocysteine, one of the essential amino acids needed in the body, among other things, for the proper functioning of the circulatory system. Cobalamin also influences the functioning of the nervous system—the construction of the myelin sheath and the formation of neurotransmitters.
The need for vitamin B12
The need for vitamin B12, as with other vitamins and minerals, depends on the patient's age, condition, and individual needs. Conditions of the stomach (gastroesophageal reflux disease, peptic ulcer) and intestines (Whipple's disease, Crohn's disease, celiac disease, Zollinger-Ellison syndrome, ulcerative colitis) increase the risk of vitamin B12 deficiency. Other factors that influence requirements include medications, especially those taken chronically—taking proton pump inhibitors, metformin, or histamine (H2) receptor antagonists can contribute to deficiency symptoms. Vegans and vegetarians are also at risk for vitamin B12 deficiency. This vitamin is found primarily in animal products—meat and organ meats—so excluding these products increases the risk of deficiency. These people are recommended to take a cobalamin supplement prophylactically.
Requirements – recommended intake per day/person:
- 1–3 years – 0.9 µg
- 4–6 years – 1.2 µg
- 7-9 years 1.8 µg
- 10–12 years – 1.8 µg
- 13 years and older 2.4 µg
- Pregnant women: 2.6 µg
- Breastfeeding women: 2.8 µg
Vitamin B12 deficiency
The daily loss of consumed cobalamin is approximately 0.1–0.2%. The basic and most frequently cited symptom of vitamin B12 deficiency is pernicious anemia, particularly megaloblastic anemia. Another deficiency symptom is changes in the nervous system: paresthesia, motor weakness, memory impairment, polyneuritis, ataxia, mood swings, cognitive impairment, mental disorders, and even lethargy. Furthermore, the effect of a vitamin deficiency on intestinal function and function has been reported.
For pregnant women and their children, vitamin B12 deficiency and/or in combination with folic acid deficiency increases the risk of preeclampsia, premature birth, intrauterine growth restriction, and megaloblastic anemia in the fetus. Furthermore, these deficiencies can lead to the occurrence of neural tube defects (WCN). These are serious fetal defects that pose a threat to the development and life of children.
Adequate vitamin B12 levels are important not only during pregnancy, but also during breastfeeding. Otherwise, a deficiency can lead to problems with the child's proper cognitive and psychomotor function.
A vitamin B12 deficiency is not immediately noticeable. Cyanocobalamin is stored in the liver and body tissues if the body does not use the entire amount consumed. These stores can last for a very long time. Often, the first symptoms of deficiency do not appear until 5-6 years after the last intake. Therefore, people suffering from a deficiency are advised to supplement this vitamin even if no symptoms occur.
Excess vitamin B12
Even in large amounts, vitamin B12 is not toxic, although severe allergic reactions can occur. Since it is a water-soluble vitamin, excess amounts are excreted in the urine. However, it should be noted that its chemical composition contains cobalt, an excess of which can cause adverse effects. There are cases where plasma vitamin B12 levels exceed 1000 pg/ml. However, this condition indicates serious disease processes, such as renal failure, hematological malignancies, liver disease, and solid malignancies.
Sources of vitamin B12
The source of vitamin B12 n is mainly animal products, although a small amount of this vitamin is also found in plant products.
Some products, including plant-based drinks, are fortified with vitamin B12 and can therefore be a source for vegans and vegetarians.
Some plants may have higher levels of vitamin B12 due to the archaea bacteria living on their surface – these bacteria influence the synthesis of this vitamin.
Another solution for vegans to supplement vitamin B12 is algae, such as spirulina. However, these usually contain an inactive vitamin B12 analogue. Therefore, it does not have the same function as vitamin B12, and consumption does not lead to a significant increase in vitamin B12 levels.
The content of vitamin B12 in example products (values are given per 100 g of product):
- Pork liver 25 mg,
- Beef fillet 1.4 mg,
- Chicken, carcass 0.4 mg,
- Turkey meat 0.7-1.4 mg,
- Salmon 5 mg,
- Milk 0.4 mg,
- Rennet cheese 1-2.2 mg,
- Cottage cheese 0.7-0.9 mg,
- Eggs 1.6 mg.
Types of cobalamin forms that exhibit biological activity
The naturally occurring forms of vitamin B12 are methylcobalamin and 5'-deoxyadenosylcobalamin. They fulfill the functions of coenzymes, which occur in enzymatic reactions. Intermediate forms in their formation are hydroxocobalamin and aquacobalamin. However, cyanocobalamin is produced synthetically. It does not occur naturally in plants but can be synthesized by bacteria that live in the digestive tract of mammals (primarily ruminants).
Other forms of B12 are also known, such as sulfatocobalamin and nitrotocobalamin, but their role in metabolic processes is unknown. Synthetically produced cobalamins also exist, such as 4-ethylphenylcobalamin, which, however, are not part of vitamin B12 but can even act as a calculus in metabolic processes and thus block the effects of vitamin B12. These forms are for research purposes only.
What influences the absorption of vitamin B12?
The bioavailability of vitamin B12 from different foods varies between 20 and 90%. It is estimated that healthy people absorb about 50% of this vitamin through food. Therefore, it is important to ensure the best possible intake of cobalamin, both in food and supplement form.
Vitamin B12 levels are influenced by:
- The presence of calcium. The cause of vitamin B12 deficiency can be malabsorption in the small intestine. Proper absorption requires a glycoprotein called Castle factor, which is secreted by the gastric mucosa. Vitamin B12 is bound by this glycoprotein in the presence of calcium.
- The presence of vitamin B6, biotin and folic acid – these compounds have a positive effect on the absorption of cobalamin.
- Technological processing of food – high temperatures and freezing – reduces the content of vitamin B12 in the product, these are not large amounts, but it is worth remembering this dependence.
- Time and place of storage – with increasing storage time and exposure to sunlight, the level of this vitamin decreases.
- Medications taken:
- Proton pump inhibitors – these medications can interfere with the absorption of B12 from food and slow the release of stomach acid.
- Chloramphenicol, a bacteriostatic antibiotic, may impair the red blood cell response to vitamin B12 supplementation in some patients.
- H2 receptor antagonists may also impair absorption
- Vitamin C supplementation – may reduce the absorption of vitamin B12, so it is recommended to leave a break of about 2 hours between vitamin C and B12 supplementation.
- Metformin – a drug used to treat diabetes – reduces the absorption of vitamin B12, possibly due to changes in the intestine and/or increased bacterial growth.
- Oral hormonal contraception,
- Cortisone,
- Cancer drugs.
