The only natural source of vitamin B12, essential for the normal functioning of the brain and nervous system, DNA synthesis and the formation of red blood cells, is food of animal origin.
For vegetarians and vegans who avoid foods of animal origin, it is necessary to supplement the vitamin intake in the daily menu with supplements.
Because without vitamin B12, or with low intake levels, the number of red blood cells decreases and a disease called megaloblastic anemia appears. It manifests itself with pale skin, palpitations, loss of appetite and weight, infertility and neuropathies.
A deficiency in this compound causes many other symptoms: motor and sensory incoordination, a feeling of numbness or tingling in the hands and feet, balance problems, depression, confusion, dementia, memory problems and ulcers in the mouth or tongue. And in babies, it affects their normal development and growth.
Foods rich in vitamin B12
In fact, vitamin B12 is produced by microorganisms, which are ingested by animals. Plants neither need it nor incorporate it, except in a few exceptions. Therefore, we obtain it mainly by eating foods of animal origin.
The main sources are the liver, kidney and brains of various animals, which provide between 50 and 100 micrograms of vitamin B12 per 100 grams of food; egg yolk, clams, oysters, crabs, sardines, salmon and chicken liver (5-50 micrograms of vitamin B12 per 100 g); and meat, whole eggs, cheese, cow's milk, cod, hake, sole and tuna (0.2-5 micrograms per 100 g).
Cooking techniques and industrial processes can affect the vitamin B12 content of foods. For example, pasteurizing milk for 2-3 seconds results in a loss of 7%; boiling it for 2-5 minutes results in a loss of 30%; and sterilizing it at 120℃ for 13 minutes results in a loss of up to 77%.
The small intestine
Bound to food proteins, vitamin B12 is released by the action of two substances secreted by the stomach, hydrochloric acid and pepsin, and binds to the R proteins of saliva and the stomach.
Upon reaching the duodenum, this bond is broken by the action of pancreatic secretions. Now free, the vitamin binds to a protein produced by the oxyntic or parietal cells of the stomach, called intrinsic factor. This process will allow it to be absorbed in the ileum, the final section of the small intestine.
Of all the vitamin B12 that reaches the intestine, we only absorb between 1 and 2 micrograms, which is considered sufficient for an optimal daily intake. Up to 1,000 to 2,000 times this amount can accumulate in the liver, so deficiencies can take several years to become apparent.
The importance of the assimilation of vitamin B12 by our body is demonstrated by a disease called pernicious anemia. This autoimmune disease destroys the parietal cells of the stomach, which are responsible for generating both the intrinsic factor and hydrochloric acid. Both are essential for separating vitamin B12 from dietary proteins and promoting its absorption by the intestine.
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How to make up for the deficit of vegetarian diets
Vegetarians, and more specifically vegans or strict vegetarians, may not be getting enough vitamin B12. Moreover , if pregnant and breastfeeding women follow such diets, the deficiency can be passed on to their babies.
Supplements can be obtained from fortified foods, especially from soy and cereals, although the supply is currently limited. Vegetable smoothies, such as those made from almonds, soy, coconut or oats, are often fortified, as are cereals or yeast.
Some forms of fermented kombucha tea, produced by a symbiosis between yeast and bacteria, indicate on their labels that they contain around 20% of the recommended daily value of vitamin B12. However, no studies have been published to support this, nor is there evidence that the vitamin present in this product is biologically active in humans.
It has also been suggested that batabatacha, a fermented black tea of Japanese origin, may contain biologically active vitamin B12. Unlike kombucha, which is made by fermenting the already prepared product, batabatacha undergoes this process while still in its leaf form.
Poorly washed plants, termites and other dubious supplements
Unconventional sources of dubious efficacy are poorly washed edible plants, as they may contain traces of vitamin B12 from bacteria present in the soil. Certain insects, such as termites, also contain vitamin B12 produced by bacteria in their intestines.
Spirulina actually contains pseudovitamin B12, which is biologically inactive in humans; there is no scientific evidence regarding its properties as a supplement.
Years ago, a study showed that fresh seaweed such as susabi-nori (Porphyra yezoensis) is effective in rats with a deficiency of this vitamin.
Nothing has been proven about chlorella, which is very popular as a dietary supplement. In general, the possibility that algae contain some active B12 derivative has not yet been reached by consensus in the international scientific community.
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