Vitamin B12 is a nutrient of concern for vegan diets because no reliable sources occur in plant-based foods.
There are many myths surrounding B12 and vegan diets, many of which are potentially harmful and may put your health at risk. This article reviews evidence-based studies to uncover what vegans need to know about vitamin B12.
The topic of B12 for vegans is complex and this article is intended to be an overview of the subject, to provide practical information, rather than a deep dive into any one topic.
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What is Vitamin B12?
Vitamin B12 is one of many essential B-vitamins. Any vitamin or nutrient that the body needs to function, but cannot make, are essential. These nutrients must be consumed through diet (or supplements) since the body cannot make it.
Vitamin B12 is also called cobalamin. The structure of vitamin B12 always contains a cobalamin molecule. Different molecules attach to cobalamin and form various analogues of vitamin B12.
Some B12 analogues are active in the body and some are not active. The body can convert certain inactive analogues into active ones.
There are only two analogues of vitamin B12 active in the body: adenosylcobalamin and methylcobalamin 1.
There is also hydroxycobalamin, found in some foods. It too can be converted into active B12 analogues in the body 1.
All other analogues of vitamin B12 are considered inactive because they do not convert into active forms of B12.
What Does Vitamin B12 Do in the Body?
Enzymes are an important group of molecules that support specific reactions in the body 1.
There are 3 main functions of vitamin B12:
- DNA production and healthy red blood cells: Vitamin B12 is part of a metabolic pathway that creates molecules needed for DNA production 1. This pathway enables the production of healthy red blood cells 1.
- Homocysteine conversion: This same metabolic pathway uses vitamin B12 to convert homocysteine into other molecules 1. Homocysteine is toxic to the body if it builds up (therefore it needs to be converted to something else) 1.
- Healthy nerve cells: Vitamin B12 is needed for healthy nerve cells and may be related to healthy aging of the brain 1.
How Much Vitamin B12 Do Vegans Need Per Day?
In contrast, the European Food Safety Authority has suggested an adequate intake of 4 micrograms of vitamin B12 per day for adults 3.
There aren’t currently any specific recommendations, by large health authorities, for intake of vitamin B12 in people relying solely on vitamin B12 supplementation (vegans). Therefore, it’s prudent for vegans to aim to meet the standard intake requirements.
There is currently no upper intake limit set for vitamin B12 1. This means intake above the recommendations is generally considered safe 1, 2, 3. It’s always best to remember, however, that more is not always better 4.
Considerations for Vitamin B12 Recommendations
There is some debate over the standard vitamin B12 intake recommendations.
B12 status tends to decrease with age, so there is some concern that the recommendations should be increased for adults over the age of 50 1. Health Canada notes that adults over 50 years of age should aim to meet intake recommendations from fortified foods or supplements (as they are more readily absorbed) rather than food sources 2.
The value of 2.4 micrograms is recommended because it’s the amount of B12 found to prevent macrocytic anemia, a common sign of vitamin B12 deficiency 3.
One study found an intake of 4-7 micrograms of vitamin B12 daily, from food sources, created optimal levels of vitamin B12 biomarkers 5. This is more in alignment to the European intake recommendations of 4 micrograms of vitamin B12 per day 3, 5.
Vitamin B12 Deficiency
Vitamin B12 deficiency can create issues including:
- Macrocytic anemia: This is the “classic” outcome of vitamin B12 deficiency. Red blood cells do not divide properly and are too large to function 1, 3.
- Homocysteine buildup: Homocysteine buildup is associated with increased risk of heart disease and Alzheimer’s disease 6, 7, 8, 9. It’s possible to not have any signs or symptoms of vitamin B12 deficiency and still have a buildup of homocysteine, putting health at risk 1, 3, 6, 7, 8.
- Nerve damage: Neurological symptoms such as weakness, abnormal sensations and mental problems can be caused by vitamin B12 deficiency 10, 11. There are different theories for how this happens10 but the point to remember is that vitamin B12 deficiency has the potential to cause irreversible (permanent) nerve damage 1, 3, 11.
Historically, vitamin B12 deficiency was caused by a lack of absorption in the body but can also be caused by not consuming enough vitamin B12 in the diet (or through supplements) 1.
Signs and Symptoms of B12 Deficiency
As a quick reference, here’s a list of signs and symptoms for vitamin B12 deficiency:
- Macrocytic anemia 1, 3
- Fatigue, loss of energy 1, 3, 12
- Tingling/ numbness in hands and feet 1, 12
- Palpitations 1, 12
- Pale skin 1, 12
- Sore tongue (glossitis) 1, 12
- Infertility 12
- Cognitive impairment (poor memory, confusion) 3, 12
- Abnormal gait (change in walking pattern) 12
- Shortness of breath 3
- Irritability 3
- Depression 3
If you have any of the above symptoms, seek medical attention. These signs and symptoms could be related to a host of other conditions, some of which may be serious.
If you have any concerns about your B12 intake or B12 status, speak to your primary care provider. Remember that nerve damage from vitamin B12 deficiency can become permanent.
How Common is Vitamin B12 Deficiency in Vegans?
There is a wide range of reported stats on B12 deficiency in vegans. The exact numbers vary greatly depending on the blood markers used and the cut-off values used to determine deficiency.
One review reported on different studies that found 30-76% of vegan adults were deficient in vitamin B12, depending on the definition of deficiency used 15.
High intakes of folate, which are possible on a vegan diet, can “mask” vitamin B12 deficiency. Specifically, high folate levels can mask macrocytic anemia but other concerns with low B12 intake can still be present 1, 11.
Signs of anemia often occur before other neurological signs and symptoms of vitamin B12 deficiency 11. However, with high folate intake, the anemia symptoms may not present and a B12 deficiency can go unnoticed until the later states (of neurological problems and potentially nerve damage) 11.
Can Veganism Cause B12 Deficiency?
The short answer is yes, a fully vegan diet can lead to vitamin B12 deficiency if reliable B12 sources are not consumed (fortified foods and/or supplements).
The more complex answer is that deficiency may take years to develop because the body stores some vitamin B12 1, 15. This store of B12 could last years before deficiency symptoms arise 1. Keep in mind that early stages of deficiency may not be symptomatic.
I have read many anecdotal claims from vegans that they have been vegan for any number of years without a B12 supplement and are doing just fine. Perhaps they’re consuming fortified foods, or perhaps they’re just lucky.
I believe these claims are dangerous, unhelpful and can put people at risk. Remember that nerve damage from B12 deficiency can become permanent and that homocysteine buildup is a risk factor for cardiovascular disease and Alzheimer’s disease 7, 8, 15.
How to Get Vitamin B12 as a Vegan
Vegan diets require vitamin B12 to be sourced from supplements or fortified foods. Fortified foods have simply had the B12 supplement added to them.
A review of B12 status of vegetarians stated:
“The official position of associations and government agencies is categorical and unequivocal: in the case of a vegetarian diet… supplementation of cobalamin [vitamin B12] is required” 11.
What Vegan Foods are High in B12?
Food sources of vegan vitamin B12 include:
- Fortified nutritional yeast (most nutritional yeast is fortified but it’s best to check)
- Fortified non-dairy products (soy milk, almond milk)
- Fortified meat alternatives (TVP, soy-based meats)
- Fortified breakfast cereals
As you can see, the key here is fortification. Vegans have the choice between taking a B12 supplement directly or consuming enough fortified foods to meet intake requirements (or a combo of both).
To date, I haven’t seen any research on how much fortified foods a vegan would need to consume to meet vitamin B12 needs if they are solely relying on fortified foods.
Reviews of the best evidence has resulted in the following recommendations:
If relying solely on fortified foods, a vegan would need to consume fortified foods at 2 different meals each day, with at least 4-6 hours between those meals 16, 18. Depending on which B12 intake recommendations you aim for (2.4 micrograms per day or 4 micrograms per day) those 2 meals should have about 2-5 micrograms of vitamin B12 16, 18.
Can Vegans Get B12 Naturally?
There seems to be a certain subset of vegans who believe B12 supplements or fortified foods are not needed and that B12 can be sourced naturally on a vegan diet.
I have seen claims that there is vitamin B12 present in numerous foods for which there is no evidence of active vitamin B12 analogues. There may be inactive vitamin B12 present, or no vitamin B12 present in these foods 17.
Some of these foods include:
- Chlorella/ spirulina and other algae
- Nori/ seaweed
- Marmite and other yeast spreads
- Soba noodles
- Fermented foods (miso paste, fermented tea, kombucha, tamari, kimchi)
- Sourdough bread
Consuming dirty foods (unwashed produce that has literal dirt on it) has also been suggested as a source of B12 for vegans. There currently isn’t evidence to support this claim 17.
Some of these foods show promise for being a plant source of vitamin B12 but more research is needed 17. In the meantime, vegans should not be led to believe these foods are a reliable way to meet vitamin B12 intake targets.
To reiterate, none of these foods have known active B12 compounds. They may contain inactive B12 analogues, but if the body can’t convert these to an active analogue, they are essentially useless 17.
For a food to be considered a reliable source of vitamin B12, it needs to be shown to consistently improve vitamin B12 levels in humans and needs to show B12 activity in the body 17.
The only reliable way to meet vitamin B12 needs as a vegan is with supplements or fortified foods.
Vitamin B12 Supplements for Vegans
There is very little research on the amount of vitamin B12 someone needs to take if they are solely relying on supplements to meet B12 intake recommendations 11. Most studies examine people who also consume active B12 in their diet (ex. from animal foods).
Absorption of B12 is a factor in determining supplement doses. The body can only absorb so much vitamin B12 at any one time 18.
So, taking smaller and more frequent doses of B12 is one strategy to meet needs, as is taking large doses less often 18. However, those larger doses typically need to be substantially larger.
With all this in mind, it’s thought that taking a cyanocobalamin supplement of 25-100 micrograms daily (or 1000 micrograms twice per week) is likely to meet intake needs 16.
There are other possible supplement regimes but these two are easy to follow. There is also the option of consuming fortified foods, as mentioned above (2-5 micrograms twice per day). This could be achieved with a small supplement twice per day as well.
Cyanocobalamin vs. Methylcobalamin
There are two main types of vitamin B12 supplements on the market: cyanocobalamin and methylcobalamin. Years ago, almost all supplements were cyanocobalamin but more recently, methylcobalamin seems to be more popular (based on my observations).
This is concerning because almost all research on vitamin B12 supplements uses cyanocobalamin. The dosage suggestions for vegan vitamin B12 intake are also based on using cyanocobalamin exclusively.
Cyanocobalamin is readily converted into both active forms of vitamin B12 the body needs (methylcobalamin and adenosylcobalamin) 1, 18. It’s also a stable molecule and the amount of cyanocobalamin absorbed with differing doses is known (has been researched) 18.
Until more research is conducted to determine adequate doses of methylcobalamin to produce and maintain favorable blood levels, vegan health experts tend to agree that sticking with a cyanocobalamin supplement is best 16, 18.
The exception to this is people who have decreased kidney function, who should work with their doctor to determine how to meet vitamin B12 needs 19.
Summary: Vegan Vitamin B12
Vitamin B12 is an essential nutrient that is not found naturally in plant-based foods. Vegans need to consume fortified foods and/or supplements to meet their intake needs.
As many as 30-76% of vegan adults are deficient in vitamin B12, depending on the definition of deficiency. To avoid deficiency, vegan adults should aim to get 2.4 to 4 micrograms of vitamin B12 each day.
If choosing a b12 supplement, choose a cyanocobalamin supplement as it’s most commonly used in research studies and can be a more reliable source of vitamin b12.
Always speak with a doctor before changing your diet or taking new supplements. Please read our full website disclaimer.
- Vitamin B12: Fact Sheet for Health Professionals
- Reference values for vitamins
- Scientific opinion on dietary reference values for cobalamin (vitamin B12)
- Elevated vitamin B12 levels and mortality
- Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population
- Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians?
- Role of homocysteine in the development of cardiovascular disease
- Hyperhomocysteinemia and Alzheimer’s disease: A systematic review
- Evidence-based prevention of Alzheimer’s disease: Systematic review and meta-analysis of 243 observational prospective studies and 153 randomised controlled trials
- Overt B12 deficiency: Nerve damage and anemia
- Vitamin B12 among vegetarians: Status, assessment and supplementation
- Vitamin B12 deficiency: Recognition and management
- Subclinical B12 deficiency and homocysteine in vegans
- B12 status of vegan adults
- How prevalent is vitamin B12 deficiency among vegetarians?
- Vitamin B12: A vegan nutrition primer
- Vitamin B12 in plant foods
- Vitamin B12: Rationale for VeganHealth’s recommendations
- Vitamin B12 and cyanide
This reference list is not intended to be comprehensive.
About Nicole Stevens
Nicole is a vegan Registered Dietitian (RD) and founder of Lettuce Veg Out.
She helps people thrive on a vegan diet with balanced recipes and easy-to-understand nutrition science.