Do we really need B12?

by Scientific Editorial Board on December 02, 2020

Vitamin B12 is a nutrient that helps keep the body’s nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.

Two steps are required for the body to absorb vitamin B12 from food. First, hydrochloric acid in the stomach separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body. Some people have pernicious anemia, a condition in which they cannot make intrinsic factor. As a result, they have trouble absorbing vitamin B12 from all foods and dietary supplements.


The amount of vitamin B12 you need each day depends on your age.

Average daily recommended amounts for different ages are listed below in micrograms (mcg):

Life Stage

Recommended Amount

Birth to 6 months

0.4 mcg

Infants 7–12 months

0.5 mcg

Children 1–3 years

0.9 mcg

Children 4–8 years

1.2 mcg

Children 9–13 years

1.8 mcg

Teens 14–18 years

2.4 mcg


2.4 mcg

Pregnant teens and women

2.6 mcg

Breastfeeding teens and women

2.8 mcg


Vitamin B12 is found naturally in a wide variety of animal foods and is added to some fortified foods.

Plant foods have no vitamin B12 unless they are fortified. You can get recommended amounts of vitamin B12 by eating a variety of foods including the following:

  • Beef liver and clams, which are the best sources of vitamin B12.
  • Fish, meat, poultry, eggs, milk, and other dairy products, which also contain vitamin B12.
  • Some breakfast cereals, nutritional yeasts and other food products that are fortified with vitamin B12. To find out if vitamin B12 has been added to a food product, check the product. (1) 


People at risk of a B12 deficiency include

  • The elderly
  • Those who’ve had surgery that removes the part of the bowel that absorbs B12
  • People on the drug metformin for diabetes
  • People following a strict vegan diet
  • Those taking long-term antacid drugs for heartburn


9 signs and symptoms of a true vitamin B12 deficiency:

  1. Pale or Jaundiced Skin
  2. Weakness and Fatigue
  3. Sensations of Pins and Needles
  4. Changes to Mobility (The damage caused by long-term, untreated B12 deficiency can affect your balance and cause changes to the way you walk and move)
  1. Glossitis and Mouth Ulcers
  2. Breathlessness and Dizziness (Anemia caused by vitamin B12 deficiency can cause some people to feel breathless and dizzy. This occurs when the body is unable to transport enough oxygen to all its cells)
  1. Disturbed Vision (In rare cases, the nervous system damage caused by a B12 deficiency can affect the optic nerve. This can result in blurred or disturbed vision)
  1. Mood Changes (Some people with B12 may show signs of a depressed mood or conditions characterized by a decline in brain function, such as dementia.)
  1. High Temperature (2)


Among its various functions, the role as immunomodulator in cellular immunity, especially in elevating the number of CD8+ cells and NK cells, attracts scientific interest. Many alternative anticancer and anti-inflammatory treatments involve the use of B12 together with other vitamins and nutrients.

Vitamin B12 plays a crucial role in the proper functioning of immune system. Methionine synthase, which uses methylcobalamin as a cofactor, is essential for the synthesis of purines and pyrimidines in all cells, including fast-dividing immune cells. Several studies (both in man and on animal models) have reported the exact function of vitamin B12 in the immune response.

B12 deficiency leads to a low number of lymphocytes and impairs the activity of NK cells (the most important for destroying cancer cells). More specifically, CD8+ cells are decreased in patients with B12 deficiency anemia when compared to control population.

Intramuscular injections with B12 (under the form of methylcobalamin) in newly diagnosed B12-deficient patients completely restore the production of CD8+ T lymphocytes, the abnormally increased CD4/CD8 ratio, the CD3−CD16+ and CD16+CD57+ count (which possess strong NK cell activity), and hence the NK cells activity. (3)

The addition of vitamin B12 significantly improved the rate of sustained virologic response (SVR) in HCV-infected patients, who were naïve to antiviral therapy. As this treatment regimen is safe and inexpensive, it proposes an option for improving the effectiveness of the HCV treatment with pegylated interferon (PegIFN) in combination with ribavirin is considered the standard of care (SOC), particularly in resource-limited settings. (4)






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