Vitamin B12 and vegan diet

It is one of the favorite topics of those who oppose the vegetarian, and therefore the vegan diet, who focus on the possible consequences of lack of this essential vitamin by the human body.

A little research on search engines will reveal how many articles have been written on this subject. Articles with contradictory conclusions and prompts towards the reader about which is the right diet, depending on the author. Of course, in order to get somewhere, one must read from many, and as reliable as possible sources, the studies, and the objective conclusions that emerge from them. This takes effort, and especially time. However, reading this article means you are willing to research the subject to a small or greater degree.

And we are here to help.

So let's make a brief presentation.

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Why do we need vitamin B12?

Vitamin B12 (cobalamin) is an important vitamin, which must be taken in small amounts by humans daily.

Some of its particularly important effects on the body are:

  • Participation in the normal function of the heart, the circulatory system, and the red blood cell production.
  • DNA protection at a biochemical level, the most important molecule of our cells (it participates in its synthesis and protection against mutations, which can lead to cancer).
  • Protection against Alzheimer's disease, and dementia in general.
  • Preservation of myelin, a protein that surrounds the nerves.
  • It works as an antioxidant (removal of harmful by-products of metabolism, such as homocysteine).

According to the Food and Nutrition Board (FNB) of the National Academy of Medicine, the recommended daily intake of vitamin B12 (in μg) depends on age and gender, as shown in the following Table.

Needs in B12

Age / Life stageMenWomen
Birth - 1st year0.4-0.5 mcg0.4-0.5 mcg
1st year - 13th year0.9-1.8 mcg0.9-1.8 mcg
14th year +2.4 mcg2.4 mcg
Pregnancy2.6 mcg
Breastfeeding2.8 mcg

                   Source: National Institutes of Health

Symptoms of vitamin B12 deficiency

Symptoms can occur due to a lack of even a small amount of B12, and become more severe and intense over time. These are:

  • Jaundice (icterus-yellowing of the skin and possibly of the white part of the eyes)
  • Anemia
  • Tongue swelling
  • Numbness and tingling of the limbs
  • Loss of balance
  • Prolonged feeling of fatigue and weakness
  • Lack of concentration (impaired learning ability)
  • Urinary incontinence
  • Illusions, hallucinations
  • Depression

Sources of vitamin B12

It is extremely difficult for a diet, vegetarian or not, to supply the necessary amounts of B12 to humans. And this is because vitamin B12 is obtained directly or indirectly from bacteria and is NOT produced by animals or plants.

Thus, our body can not create this vitamin, but it must host the bacteria that can. Therefore eating foods that have direct contact with the soil, such as roots, grasses, etc., can help increase B12 levels in the body by taking in active bacteria, which can produce this vitamin in our intestine. Of course, this doesn't mean that we should consume greens without washing them first. Washing does not completely remove the bacteria - producers of the vitamin, a sufficient amount of which settles in our intestine and produces B12.

The farmed animals are usually fed with standardized foods. As a result, they do not receive sufficient amounts of B12 either, since these foods do not contain the bacteria that produce it. So, the highly advertised meats rich in B12, are derived from animals that receive vitamin supplements through their diet or they are simply given to them in injectable form.

The difficulty of finding foods, which will contain vitamin B12 in sufficient quantities, is really great, due to other factors, such as:

  • modern cultivation methods,
  • depletion of soil nutrients,
  • pesticides,
  • the diet of animals for human consumption (the majority of animals do not graze freely in nature to receive B12 from the soil),
  • antibiotics administered which kill the bacteria that produce the vitamin
  • the hygienic conditions in which the animals are bred (very strict, resulting in the neutralization of a number of dangerous, but also non-dangerous, microbes, including those that produce B12).

By reversing the hygienic conditions for the worse, as well as all the practices of animal breeding and crop production, in theory, the production of B12 could increase. In fact, the use of manure in cultivated soils increases the production of B12. Giving animals foods mixed with manure results in higher levels of B12 in their flesh, but at the same time in extremely low hygiene indicators, obviously. The consumption of such animals by humans can lead to increased B12 levels but can be combined with other negative factors, such as much higher rates of infections.

So, do vegans suffer from vitamin B12 deficiency?

The answer is yes, but they are no more deficient than other people who eat meat.

The study of the American Journal of Clinical Nutrition, showed that 40% of the general population in Latin America suffers from B12 deficiency. And we know very well that the diet in these countries is rich in meat. Many other studies, mainly in the USA, have led to exactly the same conclusions, with a similar percentage. There, there is even greater consumption of meat! The researchers observed that consumers could not easily absorb B12 from processed foods. They could, however, absorb it in crystalline form from supplements.

What are the problems in the production of vitamin B12 by bacteria in the human intestine?

Here things become more peculiar. Vitamin B12 production and absorption is a multifactorial issue, determined by genetic (not all of us genetically have the same absorption capacity - about 20% of the population cannot absorb the vitamin efficiently) and non-genetic (lifestyle-related factors. ). It requires the existence of an internal molecule that is produced in our stomach, and joins with B12, and then they are absorbed together mainly in the intestine.

Any disturbance in this normal function can lead to partial or complete inability to absorb. Factors such as smoking, alcohol, infections, gastritis, medications, or any factor that delays the movement of food (e.g. the presence of diabetes) are directly related to B12 deficiency.

Also, a design problem of our body leads to the elimination of B12 from the body. The bacteria that produce it in our body are found mainly in the large intestine which is lower than the small intestine, where it is absorbed. Therefore, its production is done spatially after its point of absorption.

How do we ensure adequate uptake and absorption of B12?

The main vegan foods that contain vitamin B12 as a result of enrichment , and can be absorbed by our body, are:

Other foods that are not fortified, but due to symbiotic bacteria may contain the vitamin and are often found in vegan options, are:

  • kelp algae seaweeds
  • algae
  • tempeh which is a traditional Asian soy product (soy bean fermentation product)
  • Shiitake mushrooms (traditional Asian cuisine)
  • seaweed nori (sea lettuce), the well-known seaweed for making sushi, and more.

These products, however, may not contain any B12 at all or simply have substitutes of it (substances that are similar to B12 but do not have the same beneficial effect), so they can not be considered reliable sources of intake.

As reported by Harvard School of Public Health, the most appropriate diet to ensure the required B12 levels, is plant-based in combination with supplements .

Another research of the US National Institute of Health, compared and rated (based on the international standards HEI-2010 and MDS) the quality of the diet of vegans, vegetarians, semi-vegetarians, pescetarians, and omnivores. The results of the research showed that the vegan diet was the most appropriate and the omnivorous the worst.

Therefore, it is suggested:

  1. Monitoring of B12 levels with a simple blood test.
  2. Consumption of plant foods enriched in B12, two to three times a day.
  3. Taking supplements containing vitamin B12 (daily supplement with at least 25 mcg of cyanocobalamin or taken twice a week with a supplement of 1000 mcg of cyanocobalamin) methylcobalamin. The recommended quantities listed are average and are determined in particular by various factors (age, gender, physical condition) and in collaboration with a doctor or nutritionist.


Vitamin B12 is one of the hottest topics around the vegan diet for no apparent reason. Because, as it was pointed out, its low levels in humans are mainly related to other factors, and not so much to the consumption of meat. And that's because if the meat was not artificially enriched with vitamin B12, there is no way it could meet our daily needs for this vitamin.

The most satisfactory levels of vitamin B12, in omnivores and non-omnivores, are in those who take supplements, then those who consume fortified foods, and much lower in the rest of the population.

Thus, in order to get as much vitamin B12 as we need, we must all take supplements. Nowadays, people indirectly receive these supplements from B12 fortified meat, most of the time without knowing it.

So we just have to choose: Will we eat meat that is fortified with B12, or will we get it directly from supplements or properly fortified plant products?