Introduction
La vegan diet it is a nutritional regime which, if not properly managed, can favor the establishment of some nutritional deficiencies; among the many "potentials", we also find the chronic deficit 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 dairy products on the other, are collected under what are defined as the XNUMXst and XNUMXnd fundamental food groups.
Below we will try to understand first of all the basics of the vegan diet, the general information on vitamin B12, the risks attributable to a possible deficit and, finally, how to prevent or treat the chronic deficiency of this very important nutrient.
Veganism
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 all kinds and derivatives (milk and dairy products, honey, royal jelly, propolis, etc.). Of course, 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 as well.
It also eliminates drugs, supplements and cosmetics obtained through animal testing or that contain ingredients that are not allowed - including excipients - silk and wool-based clothing, and vegetables grown using fertilizers of animal origin (flour, blood, horns and bones beef, fish meal, etc.).
Vitamin B12
What is vitamin B12 and what is it used for
Vitamin B12 or cobalamin is a water-soluble vitamin of group B.
The biological roles of cobalamin are:
- promoting the transfer of an H (hydrogen) ion between two neighboring C (carbon) atoms and of the same molecule;
- reduction of ribonucleotides to deoxyribonucleotics;
- transfer of a methyl group in the same molecule.
In the mammalian organism, this results in very important functions:
- synthesis of methionine from homocysteine;
- isomerization of methylmalonylCoA into SuccinylCoA.
Ultimately, in man the vit. B12 is essential to various metabolic processes, with great involvement in:
- DNA synthesis;
- metabolism of fatty acids;
- synthesis of amino acids.
Ultimately, they seem to have a greater need for cobalamin i nerve tissues he erythrocytes (Red blood cells).
This is why cobalamin is considered a vital nutrient 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 absorbed.
This is because it must first be bound to the salivary polypeptide R in the presence of gastric acid pH, which will then yield it to Castle's intrinsic factor which is itself necessary for absorption in the small (small) intestine - not in the colon.
Understanding this process is essential to understand "why", contrary to herbivores for us also quite "close" from the evolutionary point of view, the human being 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 of methylcobalamin and adenosylcobalamin) is the exclusive prerogative of some single-celled bacterial and archae organisms.
Mushrooms lack the ability to synthesize cobalamin.
Note: the vit. Synthetic B12 used in food supplements is of the hydroxocobalamin or cyanocobalamin type.
Only by "climbing" the food chain does cobalamin travel from the microorganisms that produce it to the tissues of herbivorous animals - and then, of course, to carnivores.
For carnivores and omnivores, the primary nutritional source of vitamin B12 is muscle meat and organs, especially the 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 rabbits, after feeding process the first hard stools rich in bacterial flora which elaborate vitamin B12. Then they feed on it, absorbing the cobalamin and excreting the final feces.
The bacterial flora present in the human colon also produces a certain level of cobalamin. However, given and considered the complicated process of absorption of the same - which must take place in the small intestine and involves the intervention of saliva and gastric secretions - we can say with certainty that this cannot constitute a considerable nutritional source.
Herbivores with multiple stomachs possess a particular gastric bacterial flora responsible for the synthesis of cobalamin, which is subsequently absorbed in the intestine.
As for other herbivores that do not exploit these mechanisms instead, it is possible that they are able to reach the need for vitamin B12 thanks to the bacterial film naturally present on the food - given and considering the immense amount of vegetables that they are able to consume every day.
Some molecules such as corronoids are very similar to cobalamin but do not have the same biological activity. When taken with the diet, they can compete with vitamin B12 by compromising its absorption.
Complications from B12 deficiency
Vitamin B12 deficiency is not to be underestimated.
This deficit can be at the basis of an altered synthesis of nucleic acids, a cause of fatal complications for the embryo-fetus (especially of 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 nerve complications. It is often the cause of hyperhomocysteinemia, which some studies have evaluated as an independent cardiovascular risk factor.
The elderly with chronic vitamin B12 deficiency they might being more prone to neurological and cognitive decline.
The causes of the deficiency can be basically 2:
- Inadequate dietary intake: typical of vegan regimes that are not well organized and integrated;
- Impaired absorption: due to gastric complications (achlorhydria, gastric resection, etc.) or intestinal complications of the small intestine (small intestine resection, chronic inflammatory diseases, etc.) or due to the intake of certain drugs.
Note: as we said, taking cobalamin-like molecules (for example from algae) that are not biologically active can compromise the absorption of the biologically active one.
How much it serves
Vitamin B12 requirement
The estimated average requirement (EAR) for vitamin B12 for women and men 14 years of age and older is 2,0 μg / day. The recommended dietary allowance (RDA), on the other hand, 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 infants 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.
Also, since 10 to 30% of people elderly may not be able to effectively absorb naturally occurring cobalamin in foods, those over the age of 50 are advised to use foods fortified with vitamin B12 or a supplement.
The European Food Safety Authority (EFSA) uses the population reference intake (PRI) instead of RDA and establishes the AI ​​as follows:
- for women and men aged> 18 years 4,0 μg / day;
- for pregnancy 4,5 μg / day;
- for lactation 5,0 μg / day;
- for children aged 1 to 17 years, the AIs increase with age from 1,5 to 3,5 μg / day.
Remedies
How to find out if the vegetarian diet is not rich enough in vitamin B12
The first step is undoubtedly to understand if our body has enough vitamin B12 available.
The most common analysis is the blood dosage of total circulating vitamin B12 even if, as some insights have shown, this does not always reflect the true picture of the situation.
We know that a B12 deficiency correlates with an increase in 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, concealing the cobalamin deficiency.
On the other hand, other tests seem 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 the supplements food.
Among the enriched or fortified foods we mention:
- some vegetable drinks used as milk substitutes (so-called vegetable milks);
- some soy-based products (more frequently fermented, such as tofu, tempeh, miso);
- some breakfast cereals.
Most vegans who use fortified or enriched foods and / or specific dietary supplements get enough cobalamin.
However, a few more words should be said on the use of fortified foods. To make sure you are getting enough vitamin B12, it is always good 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 on the basis of the overall portions.
For example, if a fortified soy milk contains 1 μg of B12 per serving (e.g. 125-150 ml), consuming about 3-4 servings per day may be more or less sufficient. If there are more fortified foods in our diet, the risk of deficiency would be drastically reduced.
In general, however, the use of supplements is safer and cheaper.
