Vitamin B12 Deficiency Causes

Background

Vitamin B12 can be produced exclusively by microorganisms and is found primarily in animal sources of protein, such as meat, liver, kidney, fish, oysters, milk, in dairy products and egg yolks. It plays an essential role in DNA synthesis, the formation of red blood cells and mucous membranes, and in myelination in the nervous system.

Symptoms

Vitamin B12 deficiency manifests in hematologic, neurologic, and psychiatric symptoms. Possible symptoms include: Anemia (megaloblastic anemia), pallor, weakness, fatigue, intestinal damage, progressive demyelination of nerves, loss of appetite, diarrhea, inflammation of the tongue and oral mucosa, oral rhagades, irritability, depressive moods, memory disorders, dementia, psychosis, poor concentration, neuropathies, neurological deficits with paresthesias (formication) and muscle paresis, muscle weakness and gait disorders. Some damage from B12 deficiency is irreversible. Therefore, early detection is important. Mild (preclinical) forms without anemia are also possible. The deficiency usually does not appear for years because vitamin B12 is stored in the liver in sufficient quantities in the milligram range.

Causes

1. an insufficient intake:

  • An insufficient intake is considered rare in industrialized countries and occurs mainly as a result of vegetarian and vegan diets, alcoholism and malnutrition or undernutrition, for example, in old age.

2. a reduced intake:

  • In the case of reduced absorption, vitamin B12 is supplied in sufficient quantity with food, but it can not be absorbed into the organism. This is the case when the intrinsic factor required for absorption, which is produced by the occupant cells of the gastric mucosa, is missing. For example, due to pernicious anemia, surgical removal of the stomach, gastric surgery, infection with Helicobacter pylori and diseases of the gastric mucosa.
  • Acid is required to release vitamin B12 from food. If the acid is missing, due to insufficient formation in the stomach or acid production is inhibited by drugs such as the H2 antihistamines or proton pump inhibitors, the vitamin also can not be absorbed. Metformin and inhalation of nitrous oxide (laughing gas) are also possible causes of deficiency.
  • Vitamin B12 is absorbed in the last section of the small intestine, the ileum. Therefore, a deficiency also occurs due to inflammatory bowel disease (Crohn’s disease, celiac disease) or after surgical bowel resection. Infection with parasites (fish tapeworm) or bacteria reduces intestinal B12, as they consume it for their own metabolic processes.

3. an increased need:

  • The need is increased, for example, during pregnancy or certain diseases. However, vitamin B12 is usually substituted during pregnancy in the form of multivitamin preparations.

4. hereditary diseases:

  • Inherited genetic defects affecting proteins involved in the absorption, transport or metabolism of vitamin B12 can cause deficiency in rare cases.

Risk factors

Risk factors for developing a deficiency include a strict vegetarian diet, alcoholism, age, gastrointestinal disease, certain autoimmune diseases, pancreatic hypofunction, and long-term use of acid blockers and metformin. Age is considered the main risk factor for malabsorption.

Diagnosis

Diagnosis must be made under medical care using laboratory chemistry methods. For example, cobalamin (decreasing), holotranscobalamin (decreasing), homocysteine (increasing), and methylmalonate (methylmalonic acid, increasing) may be measured. Homocysteine and methylmalonate are substrates for enzymatic reactions in which vitamin B12 is involved. At the same time, a folic acid deficiency and an iron deficiency must be looked for. Diagnosis must exclude numerous other conditions that may cause similar symptoms, for example, diabetic neuropathy or multiple sclerosis.

Prevention

The recommended daily dose is 3 μg, and 3.5 to 4 µg daily in pregnant and lactating women (DACH Reference Values, 2010). Requirements are usually met through diet, which provides 5 to 15 µg of vitamin B12 daily.If dietary intake of vitamin B12 is insufficient, it should be substituted with medication or fortified foods.

Drug treatment

Vitamin B12:

  • Vitamin B12 is commercially available in many countries in the form of cyanocobalamin and hydroxocobalamin. Vitamin B12 is taken either orally as a tablet or injected intramuscularly for treatment. In the treatment of anemia may be deficient in iron, folic acid and potassium, because they are involved in the formation of red blood cells.

Oral administration:

  • Oral treatment is possible if the deficiency is due to insufficient intake with normal absorption in the digestive tract, for example, strict vegetarians. According to the Swiss drug information, the dosage range in this case is low at 15 to 30 µg cyanocobalamin, according to the German information at 1000 µg to 2000 µg (1-2 mg) daily. According to the scientific literature, it is also possible to treat patients with reduced absorption, for example due to pernicious anemia, orally, because approximately 1% of the vitamin B12 dose enters the bloodstream passively, independent of the intrinsic factor. The dose is then 1000 µg to 2000 µg per day.

Intramuscular administration:

Of central importance, in addition to substitution, is the treatment of the cause of the deficiency, for example, a disease of the digestive tract.