
Introduction
Vitamin B12 is a water-soluble vitamin that contains the mineral cobalt and is therefore also referred to as cobalamin.
Vitamin B12 is readily available in foods of animal origin but not available in plant-based foods. However, fortified breakfast cereals and fortified nutritional yeasts are good sources of vitamin B12 that have high bioavailability. [1]
Also, vitamin B12 has the largest and most complex chemical structure of all the vitamins.

- Vitamin B12 is processed in the stomach and the small intestine before being released into circulation and the liver takes up almost 50% of circulating nutrient. The remainder is transported to other tissues. [4,6]
- Vitamin B12 bioavailability varies with foods and is 3 times higher in dairy products than in meat, fish and poultry. [1]
- Similarly, the bioavailability of vitamin B12 from dietary supplements is about 50% higher than that from food sources. [1]
- However, absorption rates decrease with 1–2 mcg vitamin B12 and doses higher than that. [1,6]

- Although vitamin B12 is a water-soluble vitamin, the body stores an amount of the nutrient in the liver, around 1 to 5 mg which could possibly last 3-5 years. [1,5]
- Significant amounts of cobalamin are also found in the kidneys. [7]
- In case of inadequate intake, the body uses the stored nutrient levels and it might take afew years for deficiency symptoms to appear. [1]

- The excretion of vitamin B12 is proportional to body stores. [4]
- Various studies have indicated losses of 0.1 to 0.2 per cent of the B12 pool per day. [6,7]
- It is usually excreted through stools but also in the urine and through the skin. [3,4]
Body Functions

Recommended Daily Intake

Deficiency Symptoms

Vitamin B12 Food Sources

Excessive Intake/ Toxicity Side Effects
Toxicity is rare for this nutrient as it’s a water-soluble vitamin and the body removes excess amount instantly. [1,2,4]
Groups At Risk of B12 Deficiency
B12 Interaction With Other Nutrients
- Folate – Vitamin B12 plays a critical role in folate metabolism. [2,4,7]