Vitamin B12 – 12 Benefits

By-Nutrition Expert:Meena Ganagani,Practicing Clinical Nutritionist,Mumbai.

Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement

Why immune system is essential for our health

The immune system keeps a record of every microbe it has ever defeated, in types of white blood cells (B- and T-lymphocytes) known as memory cells. This means it can recognize and destroy the microbe quickly if it enters the body again, before it can multiply and make you feel sick.

Some infections, like the flu and the common cold, have to be fought many times because so many different viruses or strains of the same type of virus can cause these illnesses. Catching a cold or flu from one virus does not give you immunity against the others. (1)

Micro-nutrients for Immunity

The immune system needs multiple specific micro-nutrients, including vitamins A, D, C, E, B6, and B12, folate, zinc, iron, copper, and selenium, which play vital, often synergistic roles at every stage of the immune response. Adequate amounts are essential to ensure the proper function of physical barriers and immune cells; however, daily micro-nutrient intakes necessary to support immune function may be higher than current recommended dietary allowances.(2)

Role of Methylcobalamin(B 12) in Immunity

Methylcobalamin is a form of vitamin B12. Vitamin B12 is important for the brain and nerves, and for the production of red blood cells. Methylcobalamin is used to treat vitamin B12 deficiency. Methylcobalamin is sometimes used in people with pernicious anemia, diabetes, and other conditions. (3)

The B-vitamin complex supports many different systems and is a co factor in the regular function of many proteins and lipids. B12 contributes to the normal function of the red blood cell development and normal DNA maintenance required to keep your body in top shape.

In addition, B12 helps your metabolism by converting food into the energy that your body needs to meet the challenges of the day. Combined, these factors contribute to a healthy immune system that is ready to fight off illnesses year-round.

B12 is a water-soluble vitamin, meaning that your body does not keep a store on-hand, and so must be replenished daily. Because B12 occurs naturally in many types of food, this vitamin is readily available as a normal part of most diets. However, deficiencies can occur whether due to inadequacies in intake or mal-absorption due to a medical condition. (4)

Vitamin B12 and its Benefits

  1. Vitamin B12 plays a crucial role in the proper functioning of immune system. Methionine synthase, which uses methylcobalamin as a co factor, is essential for the synthesis of purines and pyrimidines in all cells, including fast-dividing immune cells. 
  2. Vitamin B12 could minimize the effects of protein malnutrition in the hematological or immune system
  3. Vitamin B12 carries and delivers methyl group to other molecules (including DNA and neurotransmitters). In this way, it has a significant role in cell division.
  4. Vitamin B12 has activity as a coenzyme in many enzymatic reactions.
  5. Vitamin B12participates in the synthesis of porphyrins, which are an important component of hemoglobin.
  6. Together with folic acid, it is involved in the synthesis of red and white blood cells.
  7. Without vitamin B12 folic acid cannot be absorbed and remains “trapped” in the intestinal wall (this is the reason why vitamin B12 deficiency causes the same symptoms as folate deficiency).
  8. Vitamin B12 supports the iron activity in the body and is involved in the synthesis of choline.
  9. Vitamin B12 is necessary for reproduction and stability of DNA and RNA.
  10. Vitamin B12helps the metabolism of vitamin A and more particularly absorption of carotene.
  11. Vitamin B12, together with vitamin B6, facilitates the conversion of amino acids into hormones and neurotransmitters.
  12. Vitamin B12 supports the myelin sheath around nerve structures, working together with folic acid.(5)

Vitamin B12 deficiency


  • Peripheral tingling,
  • Soreness of mouth and tongue,
  • Weakness, fatigue,
  • Loss of appetite,
  • Weight loss and constipation.

B12 is responsible for the production of high-turnover cells such as red blood cells. Therefore, in deficiency states, diseases such as megaloblastic or pernicious anemia can ensue. (6)

Vitamin B12 deficiency is a low level of vitamin B12 in your body. Vitamin B12 is only found in foods that come from animal sources such as fish, beef, dairy products, and eggs. Vitamin B12 deficiency should be treated as early as possible. Without treatment, it can cause permanent nerve damage over time. (7)

B12 status among vegetarians shows that the rates of B12 depletion and deficiency are high. It is, therefore, recommended that health professionals alert vegetarians about the risk of developing subnormal B12 status. Vegetarians should also take preventive measures to ensure adequate intake of this vitamin, including the regular intake of B12 supplements to prevent deficiency. (8)

Groups at Risk of Vitamin B12 Deficiency

The main causes of vitamin B12 deficiency include vitamin B12 malabsorption from food, pernicious anemia, postsurgical malabsorption, and dietary deficiency. However, in many cases, the cause of vitamin B12 deficiency is unknown. The following groups are among those most likely to be vitamin B12 deficient.

Older adults

Atrophic gastritis, a condition affecting 10%–30% of older adults, decreases secretion of hydrochloric acid in the stomach, resulting in decreased absorption of vitamin B12. Decreased hydrochloric acid levels might also increase the growth of normal intestinal bacteria that use vitamin B12, further reducing the amount of vitamin B12 available to the body.

Individuals with atrophic gastritis are unable to absorb the vitamin B12 that is naturally present in food. Most, however, can absorb the synthetic vitamin B12 added to fortified foods and dietary supplements.

Individuals with pernicious anemia

Pernicious anemia, a condition that affects 1%–2% of older adults, is characterized by a lack of intrinsic factor. Individuals with pernicious anemia cannot properly absorb vitamin B12 in the gastrointestinal tract. Pernicious anemia is usually treated with intramuscular vitamin B12. However, approximately 1% of oral vitamin B12 can be absorbed passively in the absence of intrinsic factor, suggesting that high oral doses of vitamin B12 might also be an effective treatment.

Individuals with gastrointestinal disorders

Individuals with stomach and small intestine disorders, such as celiac disease and Crohn’s disease, may be unable to absorb enough vitamin B12 from food to maintain healthy body stores. Subtly reduced cognitive function resulting from early vitamin B12 deficiency might be the only initial symptom of these intestinal disorders, followed by megaloblastic anemia and dementia.

Individuals who have had gastrointestinal surgery

Surgical procedures in the gastrointestinal tract, such as weight loss surgery or surgery to remove all or part of the stomach, often result in a loss of cells that secrete hydrochloric acid and intrinsic factor. This reduces the amount of vitamin B12, particularly food-bound vitamin B12 that the body releases and absorbs. Individuals undergoing these surgical procedures should be monitored preoperatively and postoperatively for several nutrient deficiencies, including vitamin B12 deficiency.


Strict vegetarians and vegans are at greater risk than lacto-ovo vegetarians and nonvegetarians of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal food. Fortified breakfast cereals and fortified nutritional yeasts are some of the only sources of vitamin B12 from plants and can be used as dietary sources of vitamin B12 for strict vegetarians and vegans. Fortified foods vary in formulation, so it is important to read the Nutrition Facts labels on food products to determine the types and amounts of added nutrients they contain.

Pregnant and lactating women who follow strict vegetarian diets and their infants

Vitamin B12 crosses the placenta during pregnancy and is present in breast milk. Exclusively breastfed infants of women who consume no animal products may have very limited reserves of vitamin B12 and can develop vitamin B12 deficiency within months of birth. Undetected and untreated vitamin B12 deficiency in infants can result in severe and permanent neurological damage.

The Academy of Nutrition and Dietetics recommends supplemental vitamin B12 for vegans and lacto-ovo vegetarians during both pregnancy and lactation to ensure that enough vitamin B12 is transferred to the fetus and infant.(9)

How to cure vitamin B12 deficiency?

  • For low intake deficiency, you may need to eat more foods that contain or are fortified with vitamin B12. You may also need to take an over-the-counter supplement.
  • For low absorption deficiency, you may need several high doses of vitamin B12 to increase your levels. These doses of vitamin B12 may be given as a shot or pill. You may need to take these vitamin B12 supplements for the rest of your life.(7)

Vitamin B12 excess

Whereas vitamin B12 deficiency has been studied intensively, the reverse situation—abnormal high levels—is rarely discussed in the literature. High plasma levels (when not associated with exterior supply) refer in all cases to some alteration in the metabolism of vitamin B12—either increased synthesis or decreased clearance of B12-binding proteins. In routine blood tests, elevated levels of B12 are found in approximately 8–15% of patients referred for the measurement. The significance of this fact still needs to be clarified and linked to clinically important outcomes. (5)

Recommended Dietary Allowances (RDAs) for Vitamin B12

AgeVitamin B12 (mcg/d)
Infants 0-12 months*0.2 mcg
Children’s(1-9 years)0.2-1.0 mcg
Boys(10–12 years)0.2-1.0 mcg
Girls(10-12 years)0.2-1.0 mcg
Boys(13-15 years)0.2-1.0 mcg
Girls(13-17 years)0.2-1.0 mcg
Boys(16-17 years)0.2-1.0 mcg
Girls(16-17 years)0.2-1.0 mcg
Men’s1.0 mcg
Women’s1.0 mcg
Pregnant Women1.2 mcg
Lactating Women (0-12 months)1.5 mcg

Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR 2010)



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