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Vitamin B12 and Vegan Diet



The vegan diet it is a nutritional regime which, if not managed properly, can favor the onset of certain nutritional deficiencies; among the many “potentials”, we also find the chronic deficiency of vitamin B12 (cobalamin).

This is fundamentally due to the exclusion of entire food groups which, in the diet of man – an omnivorous animal – perform functions that are very difficult to replace. It is certainly no coincidence that meat, fish products and eggs on the one hand, and milk and derivatives on the other hand, they are collected under what are defined as the 1st and 2nd fundamental groups of foods.

Below we will try to understand first of all the basics of the vegan diet, general information on vitamin B12, the risks attributable to a possible deficiency and, finally, how to prevent or treat chronic deficiency of this very important nutrient.


What does veganism consist of?

The vegan diet is a food philosophy based on the exclusive consumption of foods belonging to the plant kingdom (Plantae), bacteria (Bacteria) and fungi (Fungi).

It does not include any part of the animal organism (meat, offal, etc.), eggs, secretions of any kind and derivatives (milk and dairy products, honey, royal jelly, propolis, etc.). Obviously, in addition to mammals, birds, fish, crustaceans, molluscs, insects and arachnids are also excluded – let's not forget that in other parts of the world it is customary to consume these creatures too.

It also eliminates drugs, supplements and cosmetics obtained through animal testing or which contain prohibited ingredients – including excipients – silk and wool-based clothes, and vegetables grown using fertilizers of animal origin (blood meal, horns and bone beef, fish meal, etc.).

Vitamina B12

What is vitamin B12 and what is it for?

Vitamin B12 or cobalamin is a water-soluble vitamin of group B.

The biological roles of cobalamin are:

  • promote the transfer of an H (hydrogen) ion between two neighboring C (carbon) atoms of the same molecule;
  • reduction of ribonucleotides to deoxyribonucleotides;
  • transfer of a methyl group in the same molecule.

In the mammalian organism, this translates into very important functions:

Ultimately, in humans vit. B12 is essential for various metabolic processes, with great involvement in:

At the ultimate level, they appear to have a greater need for cobalamin i nervous tissues they erythrocytes (Red blood cells).

This is why cobalamin is considered a nutrient of vital importance for the correct development of the central nervous system (CNS) of the embryo-fetus and for the process of erythropoiesis (formation of the red cellular elements of the blood).

Absorption of vitamin B12

Vitamin B12 is not easily absorbable.

This is because it must first be bound to the salivary polypeptide R in the presence of acidic gastric pH, which will then release it to the intrinsic Castle factor which in turn is necessary for absorption in the small intestine (small intestine) – not in the colon.

Understanding this process is essential to understanding “why”, unlike herbivores which are also quite “close” to us from an evolutionary point of view, human beings must necessarily obtain vitamin B12 from foods of animal origin.

Where is vitamin B12 “normally” found?

The production of vitamin B12 (in its natural forms metilcobalamina e adenosilcobalamina) is the exclusive prerogative of some unicellular organisms of the bacterial and archaeal type.

Fungi do not have the ability to synthesize cobalamin.

Use: the vit. B12 is synthetic and used in food supplements hydroxocobalamin or cianocobalamina.

Only by “climbing” the food chain does cobalamin reach the tissues of herbivorous animals from the microorganisms that produce it – and then, obviously, to carnivores.

For carnivores and omnivores, the primary nutritional source of vitamin B12 is muscle meat and organs, especially liver. Useful levels are found in milk and eggs, although bioavailability is lower in the latter.

But how? In different ways.

Some herbivores, such as the rabbit, after feeding produce the first feces that are hard and rich in bacterial flora that processes vitamin B12. They then feed on it, absorbing the cobalamin and expelling the final feces.

The bacterial flora present in the human colon also produces a certain level of cobalamin. However, given and considering the complicated process of its absorption – which must take place in the small intestine and involves the intervention of saliva and gastric secretions – we can state with certainty that this cannot constitute a considerable nutritional source.

Herbivores with multiple stomachs have a particular gastric bacterial flora responsible for the synthesis of cobalamin, subsequently absorbed in the intestine.

As regards other herbivores that do not exploit these mechanisms, however, it is possible that they are able to reach their vitamin B12 requirement thanks to the bacterial film naturally present on food – given and considering the immense quantity of vegetables that they manage to consume every day.

Some molecules such as corrioids are very similar to cobalamin but do not have the same biological activity. If taken with the diet, they can compete with vitamin B12, compromising its absorption.

Complications from B12 deficiency

Vitamin B12 deficiency should not be underestimated.

This deficit may be the basis of an altered synthesis of nucleic acids, which causes unfortunate complications for the embryo-fetus (especially in the CNS).

Children deficient in cobalamin show an impaired growth process.

In adults, however, the lack of the right levels of cobalamin can lead to the onset of weakness, pernicious anemia and nervous complications. It is often the reason for hyperhomocysteinemia, which some studies have evaluated as an independent cardiovascular risk factor.

Elderly people with chronic vitamin B12 deficiency they might be more subject to neurological and cognitive decline.

The causes of the deficiency can essentially be 2:

  • Inadequate dietary intake: typical of vegan diets that are not well organized and integrated;
  • Altered absorption: due to gastric complications (achlorhydria, gastric resection, etc.) or small intestinal complications (small bowel resection, chronic inflammatory diseases, etc.) or due to the intake of certain drugs.

Use: as we said, taking molecules similar to cobalamin (for example from algae) that are not biologically active can compromise the absorption of the biologically active one.

How much you need

Vitamin B12 requirement

The estimated average requirement (EAR) for vitamin B12 for women and men aged 14 years and older is 2.0 μg/day. The recommended dietary allowance (RDA) however, is 2.4 μg / day.

The RDA for pregnancy is 2.6 μg/day and for breastfeeding is 2.8 μg/day

The RDA for children up to 12 months of adequate intake (AI) is 0.4-0.5 μg / day.

The RDA for children aged 1 to 13 years, the RDA increases with age from 0.9 to 1.8 μg/day.

Furthermore, since 10 to 30 % of people elderly may not be able to effectively absorb the naturally occurring cobalamin in foods, those over 50 are advised to use foods enriched with vitamin B12 or a supplement.

The European Food Safety Authority (EFSA) uses population reference intake (PRI) instead of RDA and establishes AIs as follows:

  • for women and men aged > 18 years 4.0 μg / day;
  • for pregnancy 4.5 μg / day;
  • for breastfeeding 5.0 μg / day;
  • for children aged 1 to 17 years, AIs increase with age from 1.5 to 3.5 μg/day.


How to find out if your vegetarian diet is not rich enough in vitamin B12

The first step is undoubtedly to understand if our body has sufficient vitamin B12 available.

The most widespread analysis is the blood dosage of total circulating vitamin B12 although, as some studies have shown, this does not always reflect the true picture of the situation.

We know that a B12 deficiency correlates to increased homocysteine ​​in the blood. On the other hand, it has been shown that very high levels of folate (typical of vegetarian diets) can compromise this correlation, hiding the cobalamin deficiency.

However, other tests appear to be more sensitive, such as, for example, the dosage of specific markers; for example the active molecular form of the vitamin, linked to a transporter, or metabolites of incomplete lipid degradation.

Vegan remedies for possible vitamin B12 deficiency

The only vegan sources reliable of vitamin B12 are foods enriched with synthetic vitamin B12 and gli supplements food.

Enriched or fortified foods include:

Most vegans who use fortified or enriched foods and/or specific food supplements take in a sufficient amount of cobalamin.

However, a few more words should be said on the use of fortified foods. To make sure you get enough vitamin B12, it's always a good idea to check food labels carefully. Knowing the cobalamin content per 100 g, it will therefore be possible to make an approximate calculation of the amount of vitamins introduced based on the overall portions.

For example, if a fortified soy milk contained 1 μg of B12 per serving (e.g. 125-150 ml), consuming approximately 3-4 servings per day might be more or less sufficient. If there are more enriched foods in our diet, the risk of deficiency would be drastically reduced.

In general, however, the use of supplements is safer and cheaper.

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