Vitamin B12 In Foods: Daily Value, Deficiency Symptoms

Nia Rouseberg Author: Nia Rouseberg Time for reading: ~12 minutes Last Updated: August 31, 2022
Vitamin B12 In Foods: Daily Value, Deficiency Symptoms

The article talks about what foods contain vitamin B12. Its use is quite extensive: the formation of blood cells, the prevention of heart disease, and even a protective effect against coronavirus infection.

In the article we will tell:

  1. The role of vitamin B12
  2. Metabolism of vitamin B12 in the human body
  3. Foods Rich in Vitamin B12
  4. Deficiency symptoms
  5. Risk Factors for Vitamin B12 Deficiency
  6. Deficiency Diagnostics
  7. Summary of Laboratory Tests to Evaluate Vitamin B12 Deficiency
  8. Recommended daily dose of vitamin B12
  9. How to make up for the lack of vitamin B12

One of the most important nutrients for the human body is cobalamin, also known as vitamin B12. Until recently, it was mentioned only briefly and only in the context of the health of the nervous system. Subsequent discoveries made it possible to boldly declare that the role of vitamin B12 was greatly devalued. The formation of blood cells, the regulation of genes, the prevention of cardiovascular diseases, and even the protective effect against coronavirus infection - the use of cobalamin should definitely not be limited to the purely practice of neurologists.

The role of vitamin B12

cofactor function

Vitamin B12 has a wide range of effects related to its cofactor function - it acts as a helper molecule for two different enzymes. The first of them, methionine synthase, neutralizes the amino acid homocysteine, the accumulation of which is recognized as an important risk factor for cardiovascular diseases: atherosclerosis, stroke, and thrombosis. In addition, the same enzyme contributes to the formation of building blocks in the DNA molecule; neutralization of histamine (mediator of inflammation) and sex hormones; supports the exchange of serotonin, dopamine and other neurotransmitters; regulates the work of genes.


The second enzyme, whose work directly depends on vitamin B12, is involved in the neutralization of toxic methylmalonic acid, which damages the outer sheath of the nerves and thereby disrupts the conduction of nerve impulses.

Maintain mental health and cognitive functions

Today it is reliably known that homocysteine ​​affects not only the functioning of the cardiovascular system, but also the conductor of the whole organism - the brain.

Nerve cells are extremely vulnerable to damage due to high oxygen consumption by the brain, significant concentrations of iron and lipids that can be oxidized, and relatively low antioxidant defense activity. In other words, this is a kind of powder keg, and homocysteine ​​is a set fire to a match that causes a powerful explosion and subsequent fire in the form of oxidative stress, leading to cognitive impairment, dementia and behavioral disorders.

Study: Vitamin B12 and health


In the red bone marrow, the blood cell factory, vitamin B12 activates the division of red blood cell precursors. Under conditions of its deficiency, they continue to grow, but do not divide - giant immature erythrocytes - megaloblasts - are formed.

Prevention of osteoporosis

A number of researchers have proposed to regard the accumulation of homocysteine ​​in the body as a new risk factor for osteoporosis.

Osteoporosis is a skeletal disease characterized by a loss of bone mineral density, structure, and strength, leading to an increased risk of fractures.

Study: Hyperhomocysteinemia is Associated with Inflammation, Bone Resorption, Vitamin B12 and Folate Deficiency and MTHFR C677T Polymorphism in Postmenopausal Women with Decreased Bone Mineral Density

It has been noted that high levels of homocysteine ​​(in conditions of deficiency of B vitamins - especially B9 and B12) increase the risk of fractures, but have little effect on bone mineral density. Presumably, this is due to the accumulation of this amino acid in the bones and its binding to collagen, one of the main proteins in bone tissue.

Study: The role of hyperhomocysteinemia as well as folate, vitamin B(6) and B(12) deficiencies in osteoporosis: a systematic review

Metabolism of vitamin B12 in the human body

The exchange of cobalamin is complex - no more than 50% of the vitamin supplied with food is absorbed by a healthy body.

Study: Vitamin B12 sources and bioavailability

Moreover, not only the content, but also the bioavailability (i.e., the ability to be absorbed) of vitamin B12 varies quite a lot depending on the type of product and even the type of meat:

type of product










Dietary cobalamin is highly protein-bound, so hydrochloric acid and gastric enzymes are critical for the release of vitamin B12. Free cobalamin in the stomach forms complexes with other protein molecules (glycoproteins) and moves to the initial section of the small intestine - the duodenum. Here, under the action of pancreatic juice enzymes, the complexes are destroyed, and vitamin B12 binds to the internal factor of Castle, a protein that ensures the absorption of B12 in the intestine.

Cobalamin is the only water-soluble vitamin that accumulates in the human body: 50 to 90% of its reserves are concentrated in the liver. The presence of reserves of vitamin B12 causes the later onset of clinical symptoms of deficiency: often they appear only after a few years.

Study: The Neuropsychiatry of Vitamin B12 Deficiency in Elderly Patients

Thus, maintaining adequate levels of vitamin B12 in the body depends on a number of factors:

  • normal secretion of gastric juice;

  • enzymatic function of the pancreas;

  • functional state of the liver and intestines;

  • contractile activity of the gallbladder.


"What to eat for breakfast with proper nutrition: ideas for healthy breakfasts for the whole family" Read more

Foods Rich in Vitamin B12

When calculating the daily intake, it is necessary to take into account the bioavailability of B 12 from specific products (see above).


The content of vitamin B12 in 100 g of product


98.9 mcg

Beef liver (raw)

59.3 mcg

Goose liver

54.0 mcg


36.0 mcg

Turkey liver

28.2 mcg

pork liver

26.0 mcg

Chicken liver (raw)

16.6 mcg


13.7 mcg


12.0 mcg


8.7 mcg


7.8 mcg

chicken hearts

7.3 mcg

rabbit meat

7.2 mcg

Chicken egg yolk

5.1 mcg

Deficiency symptoms

Usually, manifestations of vitamin B12 deficiency manifest with a general anemic syndrome, which is characterized by:

  • yellowish tint of the skin or their pallor;

  • dyspnea;

  • dizziness;

  • cardiopalmus.

In addition, manifestations associated with cobalamin deficiency are:

  • hair loss;

  • stool disorder (diarrhea);

  • lack of appetite;

  • muscle weakness and decreased muscle tone;

  • pigmentation;

  • an increase in the size of the liver and spleen on ultrasound;

  • "varnished" tongue (atrophy of taste buds);

  • lack of motivation and energy.


Disorders of the nervous system deserve special attention. Neurological symptoms are more recent (although in some cases they precede the development of anemia) and, as a rule, are irreversible. Damage to the genetic material of cells, increased excitability of neurons and impaired electrolyte metabolism in them, inhibition of the formation of new nerve connections - all these consequences of insufficient intake of vitamin B12 in the body underlie the development of dementia, including Alzheimer's disease. A growing body of research also points to a direct link between cobalamin deficiency and the development of depression.

Study: Effects of vitamin B12 and folate deficiency on brain development in children

Vitamin B12 deficiency is especially acute in newborns and young children: as you know, brain development begins in utero and continues until school age. Cobalamin deficiency leads to impaired myelination of nerve fibers and a change in the speed of impulse conduction, thereby significantly affecting the functioning of the central nervous system. As a consequence, slower conduction in the auditory and visual systems will interfere with learning and social interaction.

Risk Factors for Vitamin B12 Deficiency

Reduced intake of vitamin B12 from food
  • vegetarian diet;

  • chronic alcoholism;

  • old age.


An unbalanced vegetarian diet may be associated with a lack of nutrients, the content and / or bioavailability of which in plant products is low (this applies to iron, zinc, vitamin D, omega-3 fatty acids and vitamin B12).

In older people, vitamin B12 deficiency is often caused by:

  • malnutrition;

  • malabsorption syndrome;

  • inflammation of the gastric mucosa (which increases with age) and leads to a decrease (and sometimes complete cessation) of the secretion of hydrochloric acid, which is necessary for the release of protein-bound vitamin B12.

autoimmune thyroid disease

According to studies, vitamin B12 deficiency occurs in 46% of patients with autoimmune thyroiditis. In addition, there is a negative correlation between the levels of vitamin B12 and antibodies to the structural elements of the thyroid gland. It is assumed that this relationship is due to the presence of autoimmune gastritis: as you know, autoimmune diseases are often combined.

Study: Vitamin B12 and Vitamin D Levels in Patients with Autoimmune Hypothyroidism and Their Correlation with Anti-Thyroid Peroxidase Antibodies

Increased need for cobalamin

It has been established that during pregnancy and lactation, the need for cobalamin increases several times, and its content progressively decreases.


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The state of the human digestive system

The status of vitamin B12 is largely determined not only by a balanced diet, but also by the state of the human digestive system and the presence of all the conditions necessary for its absorption. Various factors and pathological processes disrupt the release and absorption of B12, contributing to the development of its deficiency.

Research: Modern possibilities for the diagnosis and treatment of vitamin B12 deficiency


Pathological condition

Violation of the secretion of gastric juice or a change in its acidity:

  • chronic gastritis;

  • H. pylori infection: in this case, even patients without atrophy of the gastric mucosa will be deficient in vitamin B12;

  • taking drugs that increase the pH of gastric juice: antacids, proton pump inhibitors (Omez). In addition, they promote the growth of bacteria in the small intestine, which can also increase the risk of vitamin B12 deficiency.

  • autoimmune gastritis;

  • surgical operations (including bariatric) on the stomach.

Intestinal Malabsorption:

  • chronic pancreatitis;

  • Crohn's disease, celiac disease and other autoimmune intestinal lesions;

  • parasitosis (infection with a tapeworm);

  • giardiasis;

  • excess bacterial growth.


Taking a number of drugs
  • metformin;

  • antacids;

  • H2 blockers;

  • proton pump inhibitors;

  • colchicine;

  • cholestyramine;

  • anticonvulsants and a number of antibiotics.

A number of genetic disorders
  • transcobalamin II deficiency;

  • deficiency/defect of intrinsic factor of Castle;

  • mutation in the CG1 gene.


Deficiency Diagnostics

  1. Determining the level of vitamin B12 in the blood does not reflect the intracellular concentration of vitamin B12 and the performance of its biological function. Therefore, it is possible to focus on the laboratory determination of B12 in blood serum only to identify a significant deficiency.

    • Laboratory reference: 189-833 pg/ml.

    • Optimum values: from 600 and above.


  2. Indirectly, cobalamin deficiency can be judged by the level of homocysteine ​​(but it can also reflect a deficiency of folic acid and vitamin B2) - it is optimal that its values ​​do not exceed 7 μmol / l.

  3. A fairly typical picture in the general blood test:

    • increase (closer to the upper limit of the reference) MCV - the average volume of erythrocytes.


  4. The most sensitive marker of vitamin B12 deficiency is an increase in methylmalonic acid, an analysis for organic acids in the urine.

However, it should be remembered that the concentration of methylmalonic acid often increases with kidney pathology. In addition, the measurement of its levels with concomitant antibiotics is indicative (the number of bacteria that form methylmalonic acid precursors decreases).

Study: The neuropsychiatry of vitamin B12 deficiency in elderly patients

Summary of Laboratory Tests to Evaluate Vitamin B12 Deficiency

Lab Test

Rationale for the test



Serum cobalamin

Decreased levels in vitamin B12 deficiency

Available, low price. easy to interpret

Unreliable in assessing the effectiveness of the biological function of the vitamin

methymalonic acid

Increases with vitamin B12 deficiency

High sensitivity

It is necessary to take into account other factors affecting the metabolism of methylmalonic acid, high cost.

Total homocysteine

Increases with vitamin B12 deficiency

High sensitivity

Low specificity, increases under the influence of lifestyle factors (smoking, drinking alcohol, coffee). Requires an assessment of genetic characteristics (methylation cycle).


Decreases in vitamin B12 deficiency

New test, clinical applicability unclear.

High sensitivity.

It can serve as an indicator of the availability of vitamin B12; it focuses on the amount of a transporter protein that carries the active form of B12. BUT: the active form of the vitamin is a very variable value.

(according to K. Astill-Smith and K. Reardon)

  • 0-6 months: 0.4 mcg

  • 7-12 months: 0.5 mcg

  • 1-3 years: 0.9 mcg

  • 4-8 years: 1.2 mcg

  • 9-13 years old: 1.8 mcg

  • 14 years and older: 2.4 mcg

  • Pregnancy: 2.6 mcg

  • Breastfeeding: 2.8 mcg

Daily value of vitamin B12: 6 mcg


How to make up for the lack of vitamin B12?

The main task facing the nutritionist is to find and determine the cause of the cobalamin deficiency. So, in some cases, it is enough to review the diet and make appropriate adjustments to it: for example, increase the amount of animal products consumed.

If the problem is caused by a pathology of the digestive system, the work should be complex: in tandem with a gastroenterologist. The nutritionist offers recommendations for healing the mucous membranes, improving the functioning of the digestive tract, normalizing the acidity of the stomach to activate the Castle factor.

Pathology of the gastrointestinal tract must be taken into account when choosing the method of cobalamin administration: for example, with lesions of the gastric mucosa, the sublingual (sublingual) form, which does not require the presence of hydrochloric acid, will be optimal. In addition, with a concomitant infection with Helicobacter pylori, a nutritionist may advise natural antimicrobials or a combination of them: grapefruit seed extract, oregano, colloidal silver, etc.


If vitamin B12 deficiency has developed against the background of parasitosis, then the main link in the protocols should be aimed at restoring natural protective barriers and antimicrobial factors:

  • restoration of the integrity of the mucous membranes;

  • correction of the composition and outflow of bile;

  • correction of disturbed acidity of gastric juice;

  • maintenance of the adrenal glands (without the hormones they form, it is impossible to resolve the inflammatory process).

Vitamin B12 supplementation may be considered as maintenance therapy. Although the most active form is methyl-cobalamin, in some cases (for example, with a COMT ++ mutation), it is recommended to take adenosylcobalamin or cyanocobalamin. In both cases, it is important to remember that cobalamin competes with many B vitamins, so it should be taken separately.

The material is based on research:
  • Vitamin B12 and health

  • Hyperhomocysteinemia is Associated with Inflammation, Bone Resorption, Vitamin B12 and Folate Deficiency and MTHFR C677T Polymorphism in Postmenopausal Women with Decreased Bone Mineral Density

  • The role of hyperhomocysteinemia as well as folate, vitamin B(6) and B(12) deficiencies in osteoporosis: a systematic review

  • Vitamin B12 sources and bioavailability

  • The Neuropsychiatry of Vitamin B12 Deficiency in Elderly Patients

  • Effects of vitamin B12 and folate deficiency on brain development in children

  • Vitamin B12 and Vitamin D Levels in Patients with Autoimmune Hypothyroidism and Their Correlation with Anti-Thyroid Peroxidase Antibodies

  • Modern possibilities of diagnosis and treatment of vitamin B12 deficiency

  • Impact of Helicobacter pylori on the development of vitamin B12 deficiency in the absence of gastric atrophy

  • The neuropsychiatry of vitamin B12 deficiency in elderly patients


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