Vitamin B12 in Food: A Practical Guide

Benefits of Vitamin B12 in your body  

Vitamin B12 (also known as cobalamin) is involved in the metabolism of every cell in the human body and is particularly crucial for healthy blood and neurological function.  

Vitamin B12 is the largest and most structurally complex vitamin and is made almost exclusively by bacteria.  

Vitamin B12 is required for the synthesis of fatty acids in myelin and in conjunction with folate, for DNA synthesis.  

Because there are no common vegetable sources, strict vegans must use a supplement, fortified foods or receive regular Vitamin B12 injections to avoid serious health consequences.

Vitamin B12 deficiency symptoms 

Lower intakes of vitamin B12 are associated with a wide range of conditions, including:

Factors increasing your risk of B12 deficiency

You may be at risk of B12 deficiency if you:

Satiety response 

Our satiety analysis suggests that foods containing more vitamin B12 have a strong satiety response up to around 30 mcg of B12 per 2000 calories.  This is significantly greater than the Estimated Average Requirement for vitamin B12 of 2.0 mcg/day and the Daily Reference Intake for vitamin B12 of 2.4 mcg/day.  

Vitamin B12 side effects and toxicity 

No toxic or adverse effects have been associated with large intakes of vitamin B12 from food or supplements in healthy people.  

Supplemental doses as high as 2 mg daily by mouth or 1 mg monthly by injection have been used without significant side effects.  

Because of the low toxicity of vitamin B12, no tolerable upper intake level has been set.

Stretch target for B12 

Given the strong satiety response to vitamin B12, we have set a stretch target of 34 mcg/day for men and 24 g/day for women from food.   

nutrient averageEAR RDIstretch (men)stretch (women)
Vitamin B12 (mcg)1922.43024

Availability of vitamin B12

Although we worked out how to synthesise B12 in 1970, the availability of Vitamin B12 in the food system has decreased substantially since the introduction of the 1977 US Dietary Guidelines (data from the  USDA Economic Research Service).  Thus, vitamin B12 is a nutrient that you may need to be intentional about obtaining regularly and in adequate amounts.  

Synergistic nutrients

Vitamin B12 works synergistically with vitamin A, B1, B2, B5, B6, C, E, biotin, calcium, cobalt, copper, folate, iron, methionine, omega 3, phosphate and selenium.


Vitamin B12 bioavailability significantly decreases with increasing intake of vitamin B12 (i.e. the more you eat the less you need to absorb as your body becomes replete with B12).  

As you can’t stock up on vitamin B12 (because it is water-soluble and not stored in your fat), you need to consume foods that contain it regularly.  

The bioavailability of vitamin B12 from animal products ranges from 42 to 66%.  

Interestingly, vitamin B12 in eggs seems to be poorly absorbed (i.e. less than 9%). 

The official Dietary Reference Intake is based on the assumption that healthy adults absorb 50% of dietary vitamin B12 with normal gastrointestinal function.

Some plant foods such as seaweed contain substantial amounts of vitamin B12.  However, the edible blue-green algae (cyanobacteria) used for human supplements predominantly contain pseudo vitamin B12, which is inactive in humans

The human gut produces B12, but in the lower intestine where it is not able to be absorbed for use in our body.  B12 has been measured in some plant-based foods. However, this is rare and due to “night soil” where people use their faeces to fertilise their gardens, and this is collected and consumed with the plants.  

Processing losses 

Vitamin B12 is unstable in the presence of heat, light, acid and alkali.  Losses in food range from 10 to 90%. Hence, it is important to consume fresh foods regularly.  

Vitamin B12 normal range 

The normal range for vitamin B12 in the blood is between 200 and 900 nanograms per millilitre.  People at the lower end of this range may require follow-up testing, especially if they are experiencing any of the symptoms listed above.   

Levels of vitamin B-12 are considered low if they are below 200 ng/mL. This suggests a vitamin B-12 deficiency, pernicious anemia, or an overactive thyroid. 

People with very low Vitamin B-12 levels often experience neurological symptoms.

An abnormally high vitamin B12 status is anything over 900 ng/mL. This result indicates that your body is unable to effectively clear B12 and may suggestive of liver or kidney problems, diabetes, or certain forms of leukemia.

Vitamin B12 rich food sources  


  • liver 
  • yogurt  
  • chicken 
  • steak  
  • kefir  


  • tuna 
  • mackerel
  • sardines

For a longer list, check out our Top 101 Foods High In Vitamin B12 in Nutrient Optimiser. If your goal is fat loss, select per calorie, rather than serving to get more B12 with fewer calories.

Nutrient profile 

The nutrient fingerprint chart below shows vitamin B12 is easy very to find in adequate quantities in an omnivorous nutrient-dense diet.  Foods that contain more vitamin B12 tend to have more protein, more fat and fewer carbohydrates.   

Nutrient Optimiser

If you ensure you’re getting enough Vitamin B12 (along with ALL the other essential nutrients), we’d love you to check out Nutrient Optimiser.  We have designed Nutrient Optimiser to be the quickest and easiest way to optimise your nutrition at the micronutrient level.  

You can select from our database of five hundred recipes to plan your meals for the coming week to ensure you will get the nutrients you need to thrive.  Then, if you are able to track your current diet for a few days, Nutrient Optimiser will identify the foods and meals that you need to fill your macro and micronutrient gaps. 

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