Vitamin B12 (also known as cobalamin) is a water-soluble vitamin involved in the metabolism of every cell in the human body. Vitamin B12 is the largest and most structurally complex vitamin. It is made almost exclusively by bacteria and is found predominantly in animal foods.
Roles of Vitamin B12 in Your Body
- Vitamin B12 is critical for many reactions and is particularly crucial for synthesising healthy blood cells and preventing anemia.
- Cognition and neurological function rely heavily on vitamin B12, and its deficiency has been linked to issues with memory and thought processes. B12 has also been shown to prevent the loss of neurons.
- Our mitochondria need vitamin B12 to make energy.
- B12 is one of the most fundamental vitamins for the process of methylation. Methylation helps produce neurotransmitters important for a happy mood, detoxify the body, and initiate metabolism.
- The health of the cardiovascular system depends on vitamin B12 to keep levels of inflammatory homocysteine in balance.
- Adequate B12 is vital for skin health, and deficiency has been linked to nail discolouration, hyperpigmentation, vitiligo, and acne.
- B12 is needed to protect the fetal brain and nervous system to ensure proper development and prevent congenital disabilities like neural tube defects.
- Sufficient amounts of B12 have been linked to better bone density, meaning vitamin B12 is vital for the skeletal system.
- Vitamin B12 is required in conjunction with folate for DNA synthesis. We also need vitamin B12 to absorb folate well.
- Roles of Vitamin B12 in Your Body
- What Foods Have the Most Vitamin B12?
- High Vitamin B12 (Cobalamin) Recipes
- Do Any Fruits and Vegetables Contain B12?
- How Do Vegetarians Get B12?
- Symptoms of Vitamin B12 Deficiency
- Factors Increasing Your Risk of B12 Deficiency
- Satiety Response to Foods That Contain Vitamin B12
- Vitamin B12 Side Effects and Toxicity
- Optimal B12 Target Intake
- Availability of Vitamin B12 in the Food System and Correlation With Obesity
- Synergistic Nutrients
- Bioavailability of Vitamin B12
- Processing Losses
- Normal Ranges of B12 in the Blood
- Nutrient Profile of High B12 Foods
What Foods Have the Most Vitamin B12?
Unfortunately, humans do not operate like animals and therefore must rely on varying animal foods for B12. Meat, poultry, eggs, seafood, and dairy foods are inherently great sources of B12.
You can meet your minimum daily B12 requirement with four large eggs.
Some other examples of foods high in vitamin B12 are listed below.
High Vitamin B12 (Cobalamin) Recipes
Some examples of our NutriBooster recipes high in Vitamin B12 (Cobalamin) include:
- oysters with mignonette
- quick fish salad with mussels
- seared tuna & asparagus
- Dom D’Agostino’s breakfast (pictured below)
- sea salad
Do Any Fruits and Vegetables Contain B12?
Given that B12 is either present in animal tissues or produced by bacteria, there is no fruit or vegetable source of vitamin B12 for humans. While algae contain B12, it is not usable for humans and is therefore not considered a B12 food.
How Do Vegetarians Get B12?
Because there are no common vegetable sources, strict vegans must supplement, consume fortified foods, or receive regular Vitamin B12 injections to avoid serious health consequences.
Vegan foods containing B12 are few and far between. Food sources like nutritional yeast can supply some B12, but it might not be a reliable source to truly hit your RDA. For this reason, it is highly recommended to supplement to avoid deficiency.
If you’re a vegetarian, it’s a little easier to get your B12 from food because there are ample amounts of vitamin B12 in dairy. Although vitamin B12 in present in eggs, it is absorbed poorly.
Although vitamin B12 is a water-soluble vitamin, it can be stored in the body for up to four years. This can be bittersweet because a deficiency might not be diagnosed or documented until someone is ‘in too deep’ and the symptoms of B12 deficiency may take some time to reverse.
Lower intakes of vitamin B12 are associated with a wide range of conditions, including:
- congenital disabilities,
- macular degeneration,
- cognitive impairment,
- pins and needles (paresthesia),
- a sore and red tongue (glossitis),
- mouth ulcers,
- extreme fatigue,
- memory loss, and
- low energy levels.
Because deficiency symptoms of vitamin B12 and folate are so similar, it’s essential to make sure you’re consuming enough of both nutrients if you’re experiencing any of the symptoms we’ve discussed.
The absorption of vitamin B12 mainly depends on the functioning of the gastrointestinal system. First, stomach acid separates B12 from the protein it’s attached to. It is then combined with a protein known as ‘intrinsic factor’ where it is absorbed.
If digestion is subpar or impaired, this process doesn’t happen effectively, and someone could be at risk for B12 deficiency even if they’re consuming enough B12.
Conditions like pernicious anemia result from what is thought to be an autoimmune reaction against parietal cells that create intrinsic factor. In this case, someone will need to take supplemental B12 for the rest of their life.
You may be at risk of B12 deficiency if you:
- are older,
- have poor digestion,
- have pernicious anemia,
- have or had an infection of the GI tract,
- suffer from IBS or IBD,
- have had bariatric surgery,
- follow a strict vegan diet,
- overconsuming folate (often from supplements),
- take H2 antihistamines,
- take metformin for blood sugar control, or
- take proton pump inhibitors for heartburn.
Our satiety analysis suggests that we have a strong satiety response to foods containing up to around 20 mcg of B12 per 2000 calories. As a result, people who consume foods with more vitamin B12 tend to consume 10% fewer calories overall.
This amount of B12 is significantly more 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.
For reference, the average B12 intake of our Optimisers is 12.3 mcg/2000 calories, with an 85th percentile intake of 22 mcg/2000 calories.
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 for this nutrient.
It is important to note that vitamin B12 is an antagonist of B1, and the use of B12 increases the demand for folate. With that being said, it’s essential to consume enough of both B1 and folate if you’re on a plant-based diet and supplementing with high amounts of B12 to avoid deficiencies elsewhere.
Optimal B12 Target Intake
Given the strong satiety response to vitamin B12, we have set a B12 stretch target of 12 mcg/day for men and 9.6 mcg/day for women from food.
|Vitamin B12 (mcg)||12||9.6|
Although we began synthesising B12 in 1970 and now use it to fortify foods, the availability of Vitamin B12 in the food system has decreased substantially since the 1977 US Dietary Guidelines, as shown in the chart below (produced using data from the USDA Economic Research Service). As a result, vitamin B12 is a nutrient you may need to pay more attention to ensure you obtain adequate amounts for optimal health.
Interestingly, the decrease in vitamin B12 in the food system has correlated strongly with increased obesity rates.
|Nutrient||correlation with obesity|
|sodium (g/2000 cals)||-96%|
|calcium (g/2000 cals)||-96%|
|saturated fat (%)||-92%|
|potassium (g/2000 cals)||-91%|
|vitamin A (RAE/2000 cal)||-81%|
|phosphorus (g/2000 cal)||-80%|
|vitamin B12 (mg/2000 cal)||-70%|
|magnesium (mg/2000 cal)||-33%|
These are the nutrients that the body needs alongside B12 to execute its involved functions. For this reason, it is best to consume vitamin B12 from food with the entire spectrum of these nutrients.
Bioavailability of Vitamin B12
The bioavailability of vitamin B12 decreases significantly with an increased intake of vitamin B12. Therefore, although it may seem like a paradox, your body needs to absorb less B12 as it refills its stores as you begin to consume more foods containing this nutrient.
As you can’t stock up on vitamin B12 because it is water-soluble and not stored in 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 in amounts less than 9%.
The official Dietary Reference Intake is based on the assumption that healthy adults with normal gastrointestinal function absorb 50% of their dietary vitamin B12.
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 bacteria residing in the human gut produce B12. However, it is made in the lower intestine, where it cannot be absorbed for use in our body.
B12 has been measured in some plant-based foods. However, this is typically due to using “night soil” or human faeces to fertilise gardens. As a result, the B12-producing bacteria from their stools are consumed with the plants. As you can imagine, this can have more negative health implications than benefits.
Vitamin B12 is unstable in the presence of heat, light, acid, and alkali. Losses in food range from 10 to 90% from these factors, which does not consider the loss of B12 during absorption. Hence, it is important to consume fresh foods regularly to optimise their B12 contents.
Normal Ranges of B12 in the Blood
The normal range for vitamin B12 in the blood is between 200 and 900 nanograms per millilitre (ng/mL). 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 B12 are considered low if they are below 200 ng/mL. This suggests a vitamin B12 deficiency, pernicious anemia, or an overactive thyroid.
Those with deficient Vitamin B12 levels often experience neurological symptoms and fatigue.
An abnormally high vitamin B12 status is anything over 900 ng/mL. This result indicates that your body cannot clear B12 effectively and may suggest liver or kidney problems, issues with methylation, diabetes, or certain forms of leukemia.
The nutrient fingerprint chart below shows vitamin B12 is easy very to find in adequate quantities in a nutrient-dense omnivorous diet. Foods that contain more vitamin B12 tend to have more protein and fat and fewer carbohydrates.
If you’re interested in checking if you’re getting enough (but not too much) vitamin B12 in your diet, you can check your nutrient profile using our Free 7-Day Food Discovery Challenge.
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- Maximum Nutrient Density Food List
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Nutrient Density Index
- Vitamin A
- Vitamin E
- Thiamine (B1)
- Riboflavin (B2)
- Niacin (B3)
- Pantothenic acid (B5)
- Vitamin B6
- Folate (B9)
- Vitamin B12
- Vitamin C
- Vitamin D
- Vitamin K1