Why Do Vegans Need to Take B12 Supplements?

Why do vegans need to take B12 suplements?


Switching to a plant-based diet is associated with a higher intake of complex carbohydrates, fiber, magnesium, folic acid, vitamins C and E, carotenoids and other beneficial phytonutrients.

Vitamin B12 is found in abundance in animal products such as meat, fish, eggs and dairy products. There are almost no other natural sources except algae, but we will get to those later. You probably get the picture and are starting to see why vegans need to take B12.

Vegans cannot get vitamin B12 from plant-based food, and B12 is one of the few vitamins that humans cannot produce themselves. That is why vegans need to take B12 supplements.

According to the scientific community, a properly planned vegan or vegetarian diet is suitable for all stages of life, including pregnant women, breastfeeding mothers, growing babies or children, and athletes. The term ‘well-planned diet’ also includes, among other things, a reliable intake of vitamin B12.

Although there is a consensus in the field on vitamin B12 supplementation, for some, this remains controversial. In this context, the alleged plant sources of vitamin B12, or the production of vitamin B12 in the human body, are often unjustifiably emphasized.

Don’t just take my word for it. Do your own research about Vitamin B12 at NIH website.

What is Vitamin B12?

We know there are many kinds of vitamins and each of them has a role to play in the human body. Vitamin B12 is one of them as well and oh boy, is he an important one. Kind of VIP. But why? What is vitamin B12 and what does it do?

Vitamin B12, also known as cobalamin, is an important vitamin that plays an indispensable role in the normal functioning of the nervous system and the formation of blood cells. It is produced by bacteria, which can be found in the soil, in the digestive tracts of animals, or in symbiosis with algae, and is also produced by the algae themselves.

Let me get more scientific on this. Just try to keep up.

If we do not consume B12-fortified foods and substitutes, the only dietary sources of B12 that are useful for humans are foods of animal origin.

In these foods, B12 is bound to protein and released in the acidic environment of the stomach, but in the duodenum, it is re-bound to protein by intrinsic factor secreted by the so-called parietal cells of the stomach.

The binding of B12 to intrinsic factor allows B12 to be absorbed in the ileum – the final section of the small intestine, where it is again released from protein.

What is Vitamin B12 Responsible For?

Every nerve cell in the body needs B12, as it is also responsible for the metabolism of fats, which are needed for healthy myelin sheaths which are wrapped around neurons.

Human body needs vitamin B12 because it is responsible for:

  1. The formation of red blood cells
  2. Healthy and normal brain and nervous system function
  3. Metabolism of macronutrients into micronutrients
  4. DNA formation, regulates proper growth and development
  5. Proper cell division and protects against degeneration and mutation

In addition, vitamin B12 is important for energy production. However, there is currently no evidence that taking vitamin B12 supplements increases energy levels in people who are not deficient in this vitamin.

B12 Benefits List

These are some possible health benefits of a normal amount of vitamin B12:

  1. Helps in the formation and regeneration of red blood cells and prevents anemia
  2. Helps prevent birth defects in newborn babies
  3. Positively influences bone health and osteoporosis prevention
  4. May reduce the risk of macular degeneration (eye disease)
  5. May help improve mood and prevent depression
  6. Helps preserve the brain by preventing neuron loss
  7. In people with vitamin B12 deficiency, can provide energy and eliminate fatigue
  8. May help protect the heart by lowering homocysteine levels
  9. Helps with hair, skin, and nail health

How Common is B12 Deficiency in Vegans?

Studies clearly show the presence of B12 deficiency among vegetarians and especially vegans.

Data from the well-known EPIC-Oxford study shows as many as 52% of vegans and 7% of vegetarians in the study were B12 deficient, in contrast to omnivores, who were deficient only once in a sample of 226 participants.

Furthermore, 21% of vegans and 17% of vegetarians were measured to have borderline B12 levels, again in contrast to omnivores, where only 1% were.

Not to limit the deficiency only to vegan population, people who are deficient in B12 can be roughly divided into two groups:

  1. People who do not get enough B12 from food. These are vegetarians and vegans.
  2. People who do get enough B12 (omnivores) but do not have normal absorption of this vitamin.

To dig deeper I suggest you read this article about Vitamin B12 at Vegan Society.

The Symptoms of B12 Deficiency

As human body can store vitamin B12 for up to several years, serious deficiencies are rare, but mild deficiencies are common. Over time, B12 deficiency can lead to complications such as anemia, nerve damage and fatigue.

What do I mean by »over time«? Well, B12 deficiency is aggravated over months or even years. The first symptoms do not appear until 2-6 years after the dietary intake has been interrupted or absorption has been impaired.

The progression is usually more rapid in those with impaired absorption than in those with inadequate dietary intakes. In addition to the slow progression of deficiency, non-specific symptoms also make the recognition of the disease more difficult.

Here is the list of B12 deficiency symptoms:

  • Tingling sensation, numbness in the hands, legs, feet
  • Balance problems, dizziness
  • Swollen, sore tongue
  • Memory, thinking problems, hallucinations, paranoia
  • Feeling weak, extreme tiredness

What are the First Symptoms of B12 Deficiency? What are the Worst Symptoms of B12 Deficiency?

We have listed the symptoms of B12 deficiency, now let’s break those into three stages according to severity:

  1. Minor deficiency (first symptoms).
    Even a minor deficiency of vitamin B12 can result in more frequent fatigue and lack of energy. It can even reduce the number of red blood cells, leading to anemia.
  2. Moderate deficiency (moderate symptoms).
    Problems with mental function and other neurological problems occur. Tingling sensations throughout the body and a feeling of weakness are noted. In some cases, the appearance of ulcers in the mouth and on the tongue (swollen, painful, discolored) is one of the possible signs.
  3. More severe deficiency (the worst symptoms).
    In extreme cases, severe vitamin B12 deficiency can result in major neurological problems such as forgetfulness, mood swings and even dementia.

Who is at Risk For B12 Deficiency?

Vitamin B12 deficiency poses a risk for people who have insufficient dietary intake of the vitamin, absorption problems, or taking medicines that interfere with absorption.

Risk of vitamin B12 deficiency is increased in certain groups of people which include:

  • Vegetarians and vegans
  • People over 50 years of age
  • People with gastrointestinal disorders, including Crohn’s disease and celiac disease
  • People who have had gastrointestinal surgery, fat removal surgery or bowel resection
  • People taking metformin and acid-reducing drugs
  • People who suffer from a type of anemia called pernicious anemia
  • People with specific genetic mutations such as MTHFR, MTRR and CBS
  • People who regularly consume alcoholic beverages

Find out more about Vitamin B12 deficiency at NHS website.

What Affects B12 Absorption?

B12 deficiency also increases with age in the general population, with estimates of 10-15% deficiency in people over 60 years of age and 20% deficiency over 65 years of age.

This is due to the acidity of gastric juice decreasing with age, and the low pH is necessary for the release of B12 from food, where it is bound to proteins.

Helicobacter pylori infection and the use of medications to protect the gastric mucosa (e.g. proton pump inhibitors) are also more prevalent in the elderly population, both of which also decrease the acidity of gastric juice.

Other reasons for impaired B12 absorption in the omnivorous population include pernicious anemia, small bowel surgery, bacterial overgrowth in the small bowel and some parasitic infections.

Is There a Vegan Source of B12?

Often cited sources of vitamin B12 that should also provide vegans with sufficient amounts are algae, cyanobacteria, fermented foods, (organic) vegetables with incomplete soil removal and human gut microflora.

Unfortunately, none of those have proven to be a reliable source of B12. Science says there seems to be no proper vegan B12 sources as there are no satisfactory studies that consistently confirm the efficacy of this type of B12 supplementation.

Is There B12 in Algae?

»But you mentioned algae in the beginning! « Yes, I did, but here is the thing. Algae and cyanobacteria produce B12 for their own metabolic needs, in which case the more appropriate term for B12 is cobalamin.

Humans can only use certain types of cobalamins, and those types of cobalamins that cannot be used are called B12 analogues. In the case of algae and cyanobacteria, it is mainly the production of B12 analogues that cannot be used by the human body.

Some algae produce B12 through symbiosis with bacteria, and bacteria in symbiosis with algae can also produce B12 analogues. When algae produce B12 that is useful for humans, its availability depends largely on how the algae are prepared.

A well-known example of B12 in algae is nori algae, for which some studies have confirmed the presence of ‘true’ B12, but the amount of B12 has been shown to depend on whether the algae are raw and freshly harvested or dried. Dried nori seaweed did not contain active B12.

Do Fermented Foods Have B12?

Studies suggest that fermented foods also contain some B12. Probably due to contamination during preparation, or in other cases it is thought to be produced by bacteria involved in the fermentation process. There are no large-scale studies confirming fermented foods as a sufficient source of B12.

The same is true for unwashed, organic vegetables.

What about human gut microflora? The human microflora does produce B12, but in the large intestine, where it cannot be absorbed.

Therefore, relying on vegan dietary sources of vitamin B12 is not reasonable or scientifically justified. It is for this reason that it is advisable for vegans to ensure that their B12 intake is in the form of a supplement. In this way, we get it directly from the source – the bacteria, which are the only source of B12, even when it comes to supplements.

How Many Types of Vitamin B12 Are There?

When we speak of B12 supplements, there are four types (forms) of vitamin B12:

  1. Methylcobalamin
  2. Adenosyl cobalamin
  3. Hydroxycobalamin
  4. Cyanocobalamin

All four forms are derived from bacterial production, just like the B12 found in animal foods. The difference is that B12 in supplement form is not bound to proteins in food.

Whichever form of B12 is consumed, it is always converted in the body to either methylcobalamin or adenosylcobalamin, the metabolically active forms of B12.

Which Form of B12 is Better? What Form of B12 is Best Absorbed?

Chemically, cyanocobalamin represents the most stable form of cobalamin, and is therefore the easiest to produce and the least expensive of all the forms of B12 substitutes.

There are no real differences in the absorption of the different types of B12, so it does not matter which supplement is chosen.

The toxic cyanide content, which can be disturbing with cyanocobalamin, is negligible. Cyanocobalamin should be avoided only by people with renal failure, cyanide metabolism disorders and smokers.

B12 can be supplemented in dissolved form or in the form of tablets that are dissolved under the tongue or swallowed. Both routes are equally successful in replacing B12.

Replacement by injection is also possible but is as successful as replacement by tablets.

How Much B12 a Day Do You Need?

The official recommendation is currently that an adult needs 2.4 µg of vitamin B12 daily, but several studies recommend higher amounts (estimates vary from 4-10 µg).

The gold standard for measuring adequate B12 levels is the blood concentration of methylmalonylic acid, and this is because B12 is essential for the enzymatic conversion of methylmalonylic acid to succinyl-CoA. Thus, at elevated levels of methylmalonylic acid, we can be sure that the body is deficient in B12.

Given that the 4-10 µg figure in the studies mentioned above was arrived at precisely through the measurement of methylmalonylic acid and given that the 2.4 µg figure is based on a 1958 study, it would be prudent to take higher amounts of B12 than officially recommended.

How is B12 Absorbed in the Body?

Vitamin B12 is absorbed in the intestine. 1.5-2.0 µg is absorbed actively (bound to intrinsic factor) and between 1-3% of the ingested amount is absorbed passively (via passive diffusion).

In the case of a 1000 µg vitamin B12 tablet, at least 11.5 µg is therefore absorbed, which is more than even the maximum daily recommendations. Let us remember that B12 is stored in the liver, and it is not necessary to take a supplement every day, but an average can be taken.

In the case of a 1000 µg vitamin B12 tablet taken every other day, this gives an average of 5.75 µg B12 per day, which also meets the recommendations. In principle, vitamin B12 is very safe to consume, even at levels higher than the recommendations.


Finally, let us reiterate that the vitamin B12 in supplements is produced by bacteria, which are the only source of all B12, including that found in animal foods.

As already mentioned, the problem with vitamin B12 in animal foods is that it is bound to proteins, and with age human body loses the ability to separate B12 from the proteins to which it is bound.

As life expectancy increases and the proportion of elderly people increases, B12 replacement is becoming part of the general recommendations for healthy living.

An even more obvious problem with B12 found in foods of animal origin is the association of such diets with many degenerative and chronic diseases. On the other hand, eating a whole-food plant-based diet has many health benefits. Given the availability of substitutes and the ease with which they can be consumed, vitamin B12 really is not and should not be a reason for the failure of this type of diet.

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Gregory Knox
Gregory Knox

I am a devoted father and animal lover. With a keen interest in in-depth research, I strives to provide informative and insightful content for those seeking a plant-based lifestyle.