Vitamin B12 is one of the eight B vitamins and plays an important role in cell metabolism. It is a water-soluble vitamin (i.e. it dissolves in water and after the body utilizes it,  the leftover amounts leave the body through urine). Vitamin B12 contains the mineral cobalt in its chemical structure,  thus it is known as cobalamin. Methylcobalamin is its active form and cyanocobalamin is the principal form used in supplements. It is an important vitamin that not only helps in DNA synthesis but also in protein and fatty acid metabolism.


It is not made by plants or animals but is synthesized in nature by microorganisms (bacteria). The primary source of vitamin B12 is animal-derived foods like meat and fish because animals eat food contaminated with bacteria or they produce B12 internally by their intestinal bacteria which is absent in humans. The main vegetarian source of B12 can be dairy. As our body cannot make its vitamin B12 we need to get it from our diet or supplements.


Recommend Dietary Allowances for Vitamin B12


Age Male Female Pregnancy Lactation
0 – 6 months 0.4 mcg 0.4 mcg    
7 – 12 months 0.5 mcg 0.5 mcg    
1 – 3 years 0.9 mcg 0.9 mcg    
4 – 8 years 1.2 mcg 1.2 mcg    
9 – 13 years 1.8 mcg 1.8 mcg    
14+ years 2.4 mcg 2.4 mcg 2.6 mcg 2.8 mcg


Vitamin B12 is mainly found in animal-derived foods like meat, beef, salmon, cheese, and eggs and vegetarians and vegans can get it through fortified cereal and nutritional yeasts.


Animal sources Servings Micrograms per servings Daily Value (DV)
Clams 100 grams 99 mcg 4120 %
Lamb liver 100 grams 90 mcg 3571 %
Lamb kidney 100 grams 52.4 mcg 2184 %
Sardines 100 grams 8.94 mcg 149 %
Beef 100 grams 5.9 mcg 245 %
Chicken 100 grams 0.3 mcg 12 %
Tuna 100 grams 10.9 mcg 453 %
Salmon 100 grams 4.15 mcg 208 %
Eggs 1 large boiled egg 0.6 mcg 25 %


Vegetarian sources Servings Micrograms per servings Daily Value (DV)
Spinach leaves 100 grams 0.14 mcg 5 %
Fortified cereals 100 grams 21 mcg 875 %
Swiss cheese 100 grams 3.1 mcg 128 %
Low fat milk 1 cup 1.2 mcg 51 %
Yogurt 1 cup, 200 ml 1.3 mcg 52 %
Paneer 100 grams 0.8 mcg 40 %
Whey powder 1/4th cup, 32 grams, 2 tablespoon 0.18 mcg 8 %
Whey powder isolate(purified form) 1/4th cup, 2 tablespoon 1 mcg 42 %
Nutritional yeast 15 grams (2 tablespoons) 17.6 mcg 733 %

Other sources ‐ Apple, banana, orange, blueberries, almonds and peanuts.


  1. Helps in the production of Red Blood Cells and thus prevents anemia – Deficiency of vitamin B12 inhibits RBC production and causes them to grow bigger and oval. This leads to megaloblastic anemia as the irregular RBCs are unable to migrate from bone marrow and they are unable to circulate at their average speed.
  2. Helps in the development and proper function of brain and nerve cells, thus preventing neuron degeneration– Vitamin B12 deficiency leads to brain atrophy and loss of memory in elderly people. Studies have proven that vitamin b12 along with omega-3 fatty acid has delayed mental deterioration in the early stages of dementia and helped reduce memory loss.
  3. It Aids depression symptoms and elevates mood– as it helps in the production and metabolism of the neurotransmitter serotonin which regulates mood.
  4. Prevents congenial abnormalities– Vitamin B12 is passed to the fetus by the mother via the placenta. It is necessary for the normal development of the fetal brain. Its deficiency during the first trimester of pregnancy may lead to defects in the fetus and risks of abortion or preterm labor.
  5. Support bone health and prevents osteoporosis– Its deficiency leads to decreased mineral bone density thus leading to osteoporosis and increased risk of fractures, especially in women.
  6. Reduces the risk of age-related macular degeneration which causes vision loss, particularly affecting central vision.
  7. Reduces levels of amino acid homocysteine and thus aids heart health– High levels of homocysteine in the blood cause fat deposition in blood vessels and thus increase the risk of cardiovascular diseases.
  8. Boosts body energy levels.
  9. Aids to healthy skin, hair and nails.


It happens either when the body is not getting enough amount in diet or the body is not absorbing it from food. Vegetarians and vegans are at high risk for developing a deficiency.


  1. Low dietary intake
  2. Diseases- gastritis, Crohn’s disease
  3. Gastrointestinal surgeries- like gastric bypass
  4. Chronic alcoholic


  1. Feeling tired and fatigued
  2. Sore mouth (mouth ulcers)
  3. Weight loss
  4. Loss of appetite
  5. Yellowish skin
  6. Vision problems
  7. Depressed
  8. Irritable
  9. Lack of concentration, confused
  10. Balancing problem (not a stable gait)
  11. Numbness of limbs
  12. Tingling sensation in hands and feet

Toxicity of Vitamin B12

No adverse effects are noticed with excess intake of vitamin B12 as the body keeps the required amount of vitamin and flushes the excess in urine. But rarely, megadoses can harm a certain population.

Does heating affect Vitamin B12?

Cooking does not destroy vitamin B12.  But repeated microwave heating can lead to its degradation. Therefore, one should avoid reheating food.

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