Vitamin B12: All You Need To Know

vitamin B12

In 1934 three American doctors received the Nobel Prize for the discovery of vitamin B12 (cobalamin). This is a biologically active chelate substance whose molecule contains cobalt, carbon, oxygen, nitrogen, and phosphorus. Later it turned out that there are several substances with a similar structure. Moreover, several more compounds have also been identified today that are similar to B12 but do not have its vitamin activity. For this, they received the common name Pseudo-vitamin B12.

How important is cobalamin to humans? Is it possible to do without the presence of it in the diet and what it can be replaced with?

Functions of Vitamin B12

vitamin b12 deficiency

In the human body, cobalamin does the following:

  • improves hematopoiesis, increases the number of red blood cells;
  • participates in the conversion of homocysteine ​​to methionine, which is needed for the production of DNA, the myelin sheath of nerves, serotonin, and dopamine (hormones of good mood and happiness);
  • is one of the coenzymes that regulate protein and lipid metabolism;
  • breaks down some fats and amino acids, reduces cholesterol;
  • beneficial effect on liver cells;
  • necessary for the normal functioning of the central nervous system;
  • increases mental concentration and mood;
  • affects the rate of blood clotting;
  • promotes the growth and regeneration of bone tissue, activating the division of osteoblasts.

Athletes will be interested in the fact that B12 is necessary for the synthesis of creatine. Also, this vitamin improves trophic processes in the muscles, by stimulating nervous activation which helps to increase the strength of their contractions during power loads.

Forms of Vitamin B12

The group of vitamin-like active substances useful and necessary for humans under the general name B12 includes more than 17 compounds, 3 of which are mostly used for medicinal and recreational purposes – these are:

  1. Cyanocobalamin;
  2. Adenosylcobalamin;
  3. Methylcobalamin.

Adenosylcobalamin (syn. dibencoside, cobamamide) is added to sports supplements and weight loss products as a stimulant for the breakdown of fats and amino acids. Cyanocobalamin and its more active, higher bioavailability, and expensive form, methylcobalamin, are used as an active ingredient in vitamin complexes and B12 nutritional supplements for health improvement.

Vitamin B12 Deficiency


The lack of cobalamin, the molecule of which is quite large, and therefore difficult to digest, is a fairly common problem. The cause of B12 deficiency may be due to the:

  • old age;
  • veganism, especially among people involved in sports and heavy physical labor;
  • violations of the digestive processes due to a decrease in the acidity of gastric juice;
  • pathologies of the ileum;
  • dysbacteriosis, malabsorption syndrome, Crohn’s disease;
  • reduced production of intrinsic factor Castle;
  • diseases that result in a sharp increase in the number of bacteria that feed on B12 in the small intestine;
  • autoimmune metaplastic atrophic gastritis;
  • resection of a part of the stomach or small intestine;
  • surgery to reduce body weight;
  • failure of the processes of transporting cobalamin molecules through the blood to the cells of the body, due to a violation of their binding to the mucoproteins;
  • helminthic invasions;
  • chronic pancreatitis.

B12 deficiency is common in type 2 diabetics who take metformin. Cobalamin deficiency can also occur from heartburn medications, including proton pump inhibitors, and birth control pills.

The risk group for people prone to permanent hypovitaminosis B12 includes anesthesiologists and doctors working with nitrous oxide.

B12 deficiency is also common in infants 4 to 6 months of age who are breastfed by vegetarian mothers. So far, the supply of the vitamin in the liver in such infants is limited, and at the same time it is depleted by the rapid growth rate of the baby, and the proper intake of B12 with mother’s milk does not occur.

Deficiency Symptoms

vitamin b12 foods

The list of manifestations and signs of vitamin B12 deficiency includes:

  • anemia, pallor and dry skin, brittle hair;
  • small hemorrhages on the mucous membranes;
  • pain in different parts of the abdomen, constipation;
  • neuropathy of the extremities (numbness, tingling);
  • postural hypotension;
  • depressed mood, irritability, psychosis, confusion;
  • decrease in working capacity, and physical endurance;
  • a feeling of constant fatigue, a general deterioration in well-being;
  • memory loss, dementia;
  • possible enlargement of the spleen, and liver.

Cobalamin deficiency is confirmed by an appropriate blood test. If its result is on the border of the lower B12 norm – 200–350 pg/ml, studies are also done on the plasma content of B9 (folate), homocysteine ​​, and methylmalonic acid. If necessary, additional analysis and the Schilling test are prescribed.

Consequences of Cobalamin Deficiency

The list of conditions and diseases that have arisen due to vitamin B12 deficiency includes:

  • pernicious anemia;
  • depression (especially in the elderly);
  • megaloblastic anemia;
  • polyneuropathy;
  • funicular myelosis;
  • subacute combined degeneration of the spinal cord;
  • cardiovascular diseases;
  • pregnancy complications;
  • cancer of the stomach, other organs of the gastrointestinal tract, and lung cancer.

In professional athletes and bodybuilders, vitamin B12 deficiency is the cause of poor performance.

How Much Vitamin B12 Should I Take

The daily value of B12 for a healthy person depends on age:

  • up to 6 months – 0.4 mcg;
  • from 7 to 12 months – 0.5 mcg;
  • from 1 to 3 years – 0.9 mcg;
  • from 4 to 8 years – 1.2 mcg;
  • from 9 to 13 years old – 1.8 mcg;
  • over 14 years old – 2.4 mcg;
  • pregnant women – 2.6 mcg;
  • lactating women – 2.8 mcg.

In the case of diagnosing cobalamin deficiency, the recommended daily intake of B12 increases to 1000–2000 mcg, which must be taken for at least 6–8 weeks. With neurological symptoms of B12 deficiency, high doses are indicated for several months to a year. In some cases, you will have to take cobalamin for life.

Recommended form B12:

  • tablets, 
  • capsules, 
  • powder, 
  • liquid, 
  • spray, 
  • solution for subcutaneous or intramuscular injections. 

Assimilation of oral forms is guaranteed since B12 molecules are free from compounds with product peptides.

Where Does Vitamin B12 Come From


Cobalamin is not synthesized by the human body but is produced by bacteria living in the large intestine. But since the assimilation of B12 occurs along the intestine earlier – in the thin iliac region, then its only source for us is food. Below we list the B12-containing foods (in descending order by the content of cobalamin):

  • liver;
  • ruminant meat;
  • rabbit meat;
  • chicken;
  • pork;
  • tuna liver, sardines, salmon, rainbow trout, herring, mussels, oysters, shrimp;
  • milk, yogurt, cheeses;
  • egg yolks.

In ruminants, B12 is produced by symbiotic bacteria living within the rumen. To other animals, birds, and fish, the vitamin comes from outside with animal feed, in the tissues of which there are bacteria and non-nuclear archaea that produce cobalamin.

Despite the high % content of B12 in the products listed above, a significant amount of it is destroyed during heat treatment. At the same time, the vitamin itself is poorly absorbed from foods, since in the process of digestion it is not completely released from the food proteins that bind it. As a result, less than half of the original amount enters the blood, and in egg yolk – no more than 9%. At the same time, a paradoxical phenomenon is also observed – the more a person eats foods rich in B12, the less of it is absorbed.

Plants do not produce B12. The exceptions are Nori seaweed, Shiitake, and Chanterelle mushrooms. Let’s clarify that Spirulina algae do not contain a vitamin, but pseudo-vitamin B12. It does not have vitamin activity, but it is determined in the analysis as cobalamin. With prolonged use of products or supplements with Spirulina in doses exceeding the recommended ones, it blocks the metabolism of breast cells and can cause the development of mastopathy.

Benefits of Vitamin B12

vitamin b12 side effects

Prophylactic supplementation of vitamin B12, depending on the norm for a particular age of a person, and after 60 years – 4-6 mcg per day, will have the following beneficial effects:

Prevention of anemia

B12 has an anabolic effect on the bone marrow, thereby stimulating the synthesis of red blood cells. An increase in their amount in the blood improves tissue respiration, increases efficiency, and overall endurance gives vigor, and improves well-being.

Prevention of dementia

Vitamin B12 deficiency can lead to dementia not only in the elderly but also in young people in the 25+ age category. It occurs due to the fact that cobalamin deficiency causes an increase in the concentration of homocysteine, an amino acid that is toxic to the brain and heart muscle. To improve the quality of dementia prevention and impaired cognitive functions of the brain, it is recommended to take vitamin D and/or Omega-3 in parallel with vitamin B12. It is possible that this combination will help prevent or delay the onset of Alzheimer’s disease.

Prevention of osteoporosis

It has been proven that prolonged low levels of cobalamin and high concentrations of homocysteine ​​make bone tissue fragile and trigger the development of osteoporosis. Prevention of hip fractures in the elderly is critical. Therefore, starting from the age of 45 in women and after 60 years in men, in order to prevent age-related osteoporosis, it is recommended to take calcium, vitamin D, and B12 supplements.

Prevention of heart attack and stroke

Medical scientists are also testing the association of a combination of low B12 levels and high blood levels of homocysteine ​​with an increased risk of myocardial infarction and cerebral stroke. However, the recommended approach to reduce the concentration of toxic homocysteine ​​remains the combination of B12 + B9.

Prevention of bad mood and depression

B12 is involved in the production of serotonin and dopamine. Taking cobalamin with antidepressants enhances their effect, and gives good results in the treatment of anxiety and depression. Long-term B12 self-administration is a great approach to improving your mood.

Chronic neurological pain

Since its discovery, vitamin B12 has been used to reduce the manifestation of neurological pain in both the limbs (tablets) and the back (injections). In addition, today cobalamin is prescribed for patients with diabetic neuropathy. A positive effect is achieved due to the restoration of the myelin sheath of inflamed nerves.

Recommendations For Taking B12

vitamin b12 benefits

Cobalamin is best taken separately from other vitamins, Omega-3s, and amino acids. They should be taken at least 1 hour after cobalamin. The exception is vitamin B9. You need to drink B12 and B9 in the morning, after a small amount of low-fat food. In addition, both tablets and liquid forms of vitamins are recommended to be held in the mouth for about 15 seconds and then swallowed with a small amount of water.

Recently it has become fashionable to take B12 in large quantities as a tonic. However, despite the non-toxicity of this group of biologically active chelate substances, doctors do not recommend exceeding the doses indicated in the prescription or in the instructions. The daily dose should not exceed 1500 mcg. With prolonged abuse, dermatitis, allergies, and increased blood clotting are possible.

Source: Vitamin B-12 – Mayo Clinic

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