The good old B12?
by Udo Pollmer, December 28, 2025
Irritating news is coming to light from the dark realm of hypocritical vitamin kitchens: according to the medical profession, vitamin B12 excess is now more common than deficiency. (18, 37, 66) Especially among the elderly, hypervitaminosis is up to five times more common than deficiency! (86) Until now, seniors were considered the population group most likely to be deficient in B12.
A study from France warns: "A permanently elevated vitamin B12 level...
...in plasma is closely related to solid tumours." (39) The risk of cancer was increased almost sixfold. "The increase in serum cobalamin levels occurs mainly in severe diseases," confirm Moscow doctors (53). If such correlations existed with "eternity chemicals", "glyphosate" or "fast food", there would be a huge outcry. But here, the community remains silent.
Of course, the medical profession denies any connection with its B12 treatments. Its pills and injections would, at best, normalise B12 levels. Hypervitaminosis is usually a consequence of disease and not the other way around. (73) Strange indeed: until now, B12 was a scarce commodity, but now the surplus is apparently becoming a problem – out of the blue!
Is the scene afraid of a truth that could ruin its business or even lead to claims for damages? Why does it like to investigate cases where vitamin B12 levels are significantly elevated, but no vitamin B12 therapy is known or has been admitted? In addition, there are supplements that are taken because of their advertised B12 content: for example, algae such as chlorella or spirulina, or multivitamin sweets.
A German study of patients with high serum B12 levels, which are said to have occurred without supplements, observed "many pathological conditions ... including kidney failure, haematological disorders, cancer, and liver or autoimmune diseases." (73) That's intense, isn't it?
The explanation, or should we say excuse, is: "All of these diseases can cause elevated concentrations of B12 transport proteins. In addition, liver disease can lead to increased release of B12 due to liver cytolysis and/or reduced B12 clearance." (73) In other words, it is not injections, capsules or algae, but the diseases themselves that cause excessive B12 levels.
This confusion is exacerbated by the fact that standard blood tests measure both "free" B12 and B12 bound to immune complexes. (29) Only the former is effective as a vitamin, while the latter is ineffective but causes high B12 levels. (8) These complexes can in turn mask a deficiency of free, biologically active vitamin B12. (22, 53, 80) Even in cases of clinically visible, acute deficiency, there may still be a lot of bound B12 in the blood, which is reported as "B12" in analyses. One wonders where all these immune complexes suddenly come from. In the past, they were rather the exception.
A study from Strasbourg dryly states: "High cobalamin levels (i.e. B12) were associated with high mortality rates." Here, high vitamin B12 consumption was said to have been rather rare among the patient population. (85) A meta-analysis from 2024 with over 90,000 subjects is more explicit: "Serum vitamin B12 concentration was positively associated with all-cause mortality, particularly in older people, with a linearly increasing trend." (41) The dose-response relationship suggests that B12 is the cause.
It has been known since 1968 that immune complexes are a consequence of treatment with B12, and this has now been proven many times over. (63, 64) "B12 treatment," according to a relevant quote, "was the main cause of high B12 levels." (58) These complexes are said to be of no pathological significance, even when associated with the most serious diseases. (64) After all, as every child knows, vitamins are unconditionally healthy.
It was dark, the moon was shining bright
In the past, no health problems were known to be associated with elevated levels. An overdose of vitamin B12 was considered harmless, as it would be excreted in the urine. Why are there now more and more studies finding a noticeable increase in the incidence of disease, not only in humans but also in animal experiments? After being given megadoses, mice suffered damage to their intestinal flora. Their ability to ward off germs was impaired. Instead, the vitamin promoted intestinal inflammation. (30)
Unimpressed, a self-absorbed medical profession recommends extra doses of B12 to its patients suffering from intestinal inflammation such as coeliac disease, Crohn's disease or irritable bowel syndrome. Even in cases of abnormal colonisation of the small intestine, a typical consequence of a compulsive wholefood diet, a deficiency is often diagnosed. (56) And so the customers are given extra vitamins. (31, 57)
In addition to intestinal problems, eating disorders such as veganism and the use of proton pump inhibitors for heartburn are considered to be the main causes of deficiency. (40) An important but often overlooked cause is the consumption of sucralose. This sweetener reacts with B12, causing the vitamin to lose its effect. (47) Coincidentally, even B12 supplements contain this sweetener. Purely by chance, sucralose is also the most commonly consumed sweetener.
Another cause is the willing intake of high doses of vitamin C and the trace element copper. Both destroy B12. (2, 6) Even in ordinary multivitamin mixtures, the vitamin is broken down – e.g. in injection solutions or juice bottles. (Kondo) And then avid vitamin takers wonder why they have deficiencies.
When B12 is combined with vitamin B6, the risk of hip fracture increases massively. (44) In combination with folic acid, two large Norwegian double-blind studies found a noticeable increase in lung cancer. (26) In high doses, B12 also promotes the development of glaucoma. (42) Despite this, B12 supplements are "fired off" as "protective cartridges" for glaucoma — in combination with B6, of course. (68) And multivitamins are supposed to help against hip fractures. (5) Are they all blind?
The vitamins are pseudo, the diseases are real
If, for example, a deficiency has developed due to inflammation in the gastrointestinal tract, this does not mean that B12 supplements will remedy the situation. Unfortunately, in the case of abnormal colonisation of the small intestine, the overgrown intestinal flora (SIBO, known as overgrowth syndrome) converts B12 into so-called pseudovitamins. (10) In higher doses, these can exacerbate a deficiency because they block the real vitamin at the transporters – even if the person is consuming enough real B12. (11) A high intake of "B12" can therefore have the opposite effect in the long term to what the therapist or patient hopes for.
The term "pseudovitamin" is confusing because it is used in different ways. Sometimes it refers to all B12-like compounds that are not B12, sometimes only to a very specific compound. In this case, the other pseudovitamins are considered "analogues". Not only do they lack vitamin efficacy, they are also harmful to health because they cause a vitamin B12 deficiency. The more analogues there are in the body, the less effectively it utilises the real vitamin.
Even real B12 is not a specific substance, but rather a collective term for several very similar molecules. Standard analysis usually detects all of them, whether pseudo or not, and reports them as "B12". This is a stroke of luck for suppliers of dubious B12 preparations.
Of course, the body tries to protect itself from pseudo-vitamins in everyday life. First, the real B12 – and only this – binds to transcobalamin I from saliva. The stomach contributes the intrinsic factor, to which the B12 is transferred in the intestine. There, the complex binds to the cubilin receptor. In the intestinal mucosa, the intrinsic factor is removed from the complex again and coupled to transcobalamin II. This protein is produced in the liver, among other places. Only now can the B12 be absorbed by the body's cells.
After use, the vitamin undergoes enterohepatic circulation. This ensures that nothing is lost. The body checks the B12 molecules excreted by the bile for their biological effectiveness. Only intact, genuine B12 is reabsorbed. Damaged molecules or pseudovitamins are excreted. Even bacteria in the healthy human intestinal flora are able to distinguish real B12 from pseudovitamins. (21) The false vitamins are excreted first via the faeces. (3) Real B12 usually comes from the intestinal flora. (46) Absorption is no longer possible in the colon.
Now it becomes clear why the body goes to such ridiculous lengths. It finds pseudovitamins so repugnant that it operates a multi-stage safety system. "These transport systems appear to protect humans and animals from the potentially harmful effects of naturally occurring cobalamin analogues." (3) In this way, the body prevents a dangerous deficiency of genuine B12.
Deficiency of vitamin k = knowledge
Trace amounts of B12 are sufficient for the body. Since this vitamin is actually vital, the body stores it for lean times as a precaution. This usually lasts for a decade. The total amount stored in the human body is estimated at two to three milligrams. In healthy individuals, a deficiency is only possible if they completely abstain from animal products. Even occasional consumption of animal products provides sufficient B12. Provided that too many pseudovitamins do not interfere.
Newborns are usually born with a reserve of B12. However, children of vegan mothers have developed deficiency diseases such as pernicious anaemia because the pregnant women themselves lacked the necessary reserves; the woman's body keeps the scarce remaining reserves for itself.
With age, however, the ability to absorb B12 diminishes. Older people are therefore given a whole "course of treatment" in the form of injections. This involves six megadoses – in this case, one or two milligrams each. This is to ensure that there is enough, because the body only uses a small part of each injection. (57)
Megadoses are now also administered orally, as a small amount will always seep into the tissue. (57) The idea of oral administration, without any injections, gave the B12 hype a new boost. To give you an idea of what the body thinks of it: it absorbs a good half of 1 µg, only 3% of 50 µg and just over 1% of 1000 µg. 1000 µg is 1 mg, which is the usual therapeutic dose. An injection of 1000 µg is still 150 µg, or 15% of the dose. (15)
Whether this also triggers the formation of pseudovitamins and immunoglobulins is a matter of speculation. This is because the complex biochemical control of absorption, which serves to absorb only genuine B12, is simply flooded; doctors refer to this as transporter- -independent absorption. (57) Pseudovitamins accumulate mainly in the liver, and to some extent also in the erythrocytes and brain. (38)
Cash cows
In the search for sources of income, diabetics have proven to be a lucrative cash cow. The popular belief that their medication metformin causes a deficiency (65), which in turn promotes neuropathies and a string of other diseases, can have unexpected consequences: "Our results," according to a study of 3,500 diabetics "who were given this vitamin as a supplement, showed a statistically significant increase in serum vitamin B12 levels, along with liver, blood, breast, kidney, thyroid and neurological diseases, as well as various solid tumours." (1). Good night, Marie!
This spectrum of diseases sounds less like pseudovitamins and more like algae toxins. To make matters worse, some of these toxins also cause diabetes by attacking the pancreas. (82, 83) This should have long since caused alarm in the field of diabetology — but, as luck would have it, algae, including spirulina, are highly recommended to diabetics as a source of B12.
However, algae cannot produce B12, regardless of whether they are wakame, chlorella or nori (porphyra). Instead, they contain inactive B12 analogues, i.e. pseudo-vitamins. (20, 79, 81) If so, they originate from bacterial contamination (7). This also applies to kombu algae, which Japanese chefs value as a flavour enhancer. It may well be that bacterial B12 is also present. But when it is shipped to Europe in dried form and stored in transparent bags at the customer's premises, the highly sensitive vitamin evaporates down to the last molecule in the cooking pot at the latest. All that remains, if anything, are algae toxins.
If algae contain real B12, then it comes either from faeces or bacteria. It seems to be sufficient to cultivate algae in open tanks: the dirtier the broth, the more vitamin. The cleaner the facility, the poorer the yield. (72)
Currently, a special variety of sea lettuce, the green algae Ulva fenestrata, is attracting great interest as a source of B12. (69) In exceptional cases, this may even be true: these algae are "fattened" in the tasty wastewater from fish processing plants. (67) Offal, especially from herring, is said to be particularly rich in B12. (48) And where do herring get it from? From seawater. It is produced there by the bacterium Thaumarchaeota and absorbed by phytoplankton. It accumulates through the food chain. (79) That is why fish is a primary source of B12.
The same applies to plants: here, too, faecal contamination may have contributed to the vitamin content; for example, duckweed, a new star in the sky above Veganistan. The ducks send their regards. Or perhaps the rule "After using the toilet and before eating, don't forget to wash your hands" did not receive the necessary attention in the laboratory; perhaps in order to finally be able to present results that please the zeitgeist and are conducive to one's career?
Fungi cannot synthesise the vitamin any more than algae or plants can; however, they absorb it from the substrate if faecal B12 is present in the form of manure or if bacteria that produce B12 live in it. (79) This could explain, for example, the B12 levels found in sea buckthorn. Of course, fungi also provide pseudovitamins. Therefore, like plants or algae, they are not recommended. Unless the customer knows which bacteria were present in which compost and which shrubs and fruits thrived on it?
Insects are probably no exception, unless they are faecal-affine like blowflies, cockroaches or dung beetles. As expected, the promised B12 in crickets turned out to be pseudo- e B12. (Okamoto) Mussels are said to contain real B12, (4) but unfortunately they filter algae toxins from the water and accumulate them (14). So they are questionable candidates. The safest sources of vitamins are still ruminants, predatory fish and liver.
Fruit flesh thanks to bacteria
Fermented products are considered promising sources of B12, such as tempeh, a soy product produced with moulds of the genus Rhizopus. The B12 initially discovered in it later turned out to be a pseudovitamin. It was produced by a bacterium called Klebsiella pneumoniae, which had contaminated the starter culture as an impurity. (4) Thus, a cute pathogen that causes pneumonia has sparked enthusiasm in vegan cuisine. Sauerkraut, sourdough and probiotics such as lactobacilli also provide only pseudovitamins instead of B12. (62)
As a cautious look into the future, it is worth mentioning non-alcoholic beer, which apparently contains a little real B12. The source is Propionibacterium freudenreichii, which brewers use to ferment their drink. However, the amounts of B12 are so small that it is not (yet) worth drinking a non-alcoholic beer with your grilled sausage. The sausage contains enough B12. Unfortunately, Propionibacterium also produces pseudovitamins. (17, 23)
This bacterium is suitable for the biotechnological production of B12 (52) and even thrives on food industry waste such as old cooking fats (13, 32), especially in combination with extra cobalt (17). However, the element is feared due to its enormous toxicity, even though it is sometimes used for doping. (54)
This has naturally aroused the interest of the industry, which is considering, for example, upgrading its press residues or molasses using propionic bacteria. The bacteria break down sugar, producing the preservative propionic acid (E 280). (52) With modern genetic engineering techniques, it is only a matter of time before the fruit "flesh" in nectar entices consumers with the promise that it is "as rich in vitamins as a small steak".
Spirulina: not fish, not meat, not even algae
Spirulina is a supposed algae that is said to provide B12. In reality, it is a cyanobacterium that has been genetically modified many times for commercial use. Even though spirulina itself does not produce any of the known algae toxins, it is often associated with its toxin-producing relatives. In the USA, the authorities therefore require the use of a defined strain to ensure that the end product is free of microcystins. Another cyanobacterium is the so-called blue-green algae Aphanizomenon flos-aquae, or AFA algae for short, which has also been found to contain cyanotoxins. (25, 36)
A review of nearly 100 "microalgae" growers in France revealed that the small-scale industry apparently has no real idea what is floating around in its ponds and tanks. Instead of the correct species, a good dozen foreign cyanobacteria were thriving in the nutrient solutions. (51) One can only speculate as to what the situation might have been like in the many businesses that refused to be inspected. What toxins these uninvited "guests" produce remains unknown.
Spirulina cultures thrive on wastewater. According to experts in Asia, pig manure is not only a good way to make optimal use of its nutrients, but also to purify wastewater. (12. 16) The ecological balance is excellent, as is the economic efficiency. At the same time, it explains claims that spirulina contains vitamin B12, as B12 is a typical indicator of faecal matter.
China is a major exporter of "natural" B12, as many customers expect. While only 3 tonnes of B12 were produced worldwide in 1989, presumably mainly through chemical synthesis , production in China alone reached over 30 tonnes in 2020. (13) Asia's pigs grunt happily when they think of Europe's vegans.
Is it a coincidence that the spectrum of diseases associated with high B12 levels is reminiscent of cyanotoxin poisoning? Pseudovitamins cause deficiencies, which is bad enough, but cyanotoxins cause a wide range of serious clinical pictures, depending on the toxin. The microcystin group alone comprises 279 known structures to date. (33) Toxicologists have repeatedly found cyanotoxins in "algae" supplements, with limits, where they exist at all, being exceeded by up to 50 times. Cyanotoxins destroy the liver, some cause cancer, and some damage the nerves and brain. (19, 24, 35, 59, 61, 76)
In the case of Alzheimer's, there is a direct link: a disproportionate number of "inactive" B12 molecules, i.e. pseudovitamins, (43) were found in the blood of patients, as they dominate in spirulina and algae preparations (27, 34, 77, 78). At the same time, however, they can be contaminated with cyanotoxins. This group of people in particular is often given supplements. (71)
"The brain is of particular concern, as microcystin has been shown to cross the blood-brain barrier and cause neurodegenerative pathologies." (33) Not only the well-known BMAA, but also microcystins such as MC-LR. (9, 60) They are typical of algae of all kinds, especially those sold as a source of B12. (74, 84)
The aforementioned proton pump inhibitors for heartburn provide further evidence. "Neurological side effects ... include cognitive impairment, neuropathies, depression, anxiety and hallucinations," according to the medical press. (45) The pills may be innocent; the effect is more likely to be due to attempts to treat the impending B12 deficiency with high-dose preparations. The same can be assumed in some cases of intestinal inflammation.
Yes, but the Japanese ...
... they eat seaweed like Germans eat bread here? Seaweed such as Ulva fenestrata could even replace meat. Seaweed is a superfood and the reason why Japanese people live to a ripe old age.
Nothing could be more absurd: hunger drove people to eat it, not vegan health fanaticism. Seaweed has always been food for poor devils. Over time, they found ways and means to make some varieties edible through appropriate preparation. Today, Japanese cuisine uses kombu seaweed to imitate meat broth and nori seaweed as wrapping paper for rice rolls (sushi). Ulva species replace green salad. No matter how you look at it, you can't make chicken skewers, steak or schnitzel out of it.
The focus of processing is on detoxification. Take hijiki seaweed, for example: after harvesting, it is dried until it turns black. The colour comes from the inedible pigment phlorotannin. It tastes bitter and acrid and helps the seaweed defend itself against predators such as dinoflagellates. (88, 91)
To reduce the toxic phlorotannin content, the mass is boiled for hours with brown algae such as Eisenia bicyclis. To remove the remaining phlorotannin, the whole mixture is steamed again for many hours. Before consumption, the dried hijiki is boiled again, for example with soy sauce and sugar, to make a garnish for rice. Does anyone really believe that Japanese people pay attention to the sensitive B12 in their seaweed? Given their fish consumption, Japanese people certainly have no need to pay attention to their B12 intake.
However, even careful processing cannot transform hijiki seaweed into a "healthy" food. Hijiki accumulates arsenic. (92) Just 3 per cent seaweed in rat feed leads to poisoning. (94) Health authorities in Asia are now warning their populations. If necessary, citizens may boil their hijiki thoroughly and then discard the water. However, it would be healthier to avoid it altogether.
Fortunately, the algae products used by our food industry are generally purified raw materials such as alginates (E 400 – 404), agar-agar (E 406) or carrageenan (E 407). The potential nutritional value of algae is of no interest whatsoever; the only thing that matters here is its technical suitability for increasing the variety of confectionery and desserts. So far, no one has come up with the idea of promoting the algae products contained in these foods as a guarantee of health and eternal life.
Where people cannot afford meat or bread, they chew algae in their distress. This also happened at times on Germany's coasts, for example during the hunger winter of 1946/47. When a population has to consume certain foods for generations, their digestion tries to adapt to the food. This is what happened in Northern Europe with milk and its lactose, and it happened in Japan with algae. That is why the Japanese have intestinal flora that is capable of digesting algae.
The enzymes were taken over from marine bacteria such as Zobellia galactanivorans and integrated into the genome of intestinal bacteria such as Bacteroides plebeius (Phocaeicola plebeius). They allow red algae of the genus Porphyra (e.g. nori) to be used for caloric energy. (89, 90, 93)
It is a sign of ignorance to present local diets, especially those born out of necessity, as a model for the world. They are not a model, but rather the intersection of the resources and digestive enzymes or metabolism of the inhabitants. Japanese people can digest algae. Most Europeans cannot. The forced consumption of algae can also be seen in the disease "Hashimoto's", which is caused by the notoriously high iodine content of many algae. It is no coincidence that this thyroid disorder was named after a Japanese doctor.
Those who measure here often measure rubbish
To date, there is no reliable and affordable routine method for measuring true B12 in the blood. Vitamin B12 analyses are challenging, not only because of the extremely low concentrations, instability, high sensitivity to light and, as a result, their similar degradation products.
The commonly used immunofluorescence method also measures pseudovitamins, as does the widely used microbiology method. For this reason, surrogate markers such as methylmalonic acid, holo-transcobalamin or total homocysteine are often used as benchmarks. However, these markers are also prone to error. (28, 49) Many methods require not only analytical specialists, but also expensive equipment and reagents such as radioisotopes. All in all, it is a risky business for the patient.
The sheer number of methods alone shows how dissatisfied analysts are with what is currently available. There is chemiluminescence, fluorescence spectroscopy, surface plasmon resonance, HPLC-PDA analysis, Raman spectroscopy and reversed-phase liquid chromatography (RP-LC), electrochemical sensors and nanosensors, ELISA kits and paper chromatography, to name but a few (70). Even the widespread use of cyanidation prior to determination with LC-MS/MS or HPLC/UV is not always effective because it does not differentiate between the various forms? (46, 55, 75)
Smoke and mirrors
Everyone wants B12 these days — not just vegans and the elderly. The vitamin has become a lifestyle product, consumed indiscriminately from infants to the very old. The same is true in livestock farming: even pig feed is supplemented now. After farm animals, the hype has now reached our pets as well.
But how is the booming market supplied with goods? What role do "spirulina preparations" made from pig manure or algae from sewage containing pseudo-vitamins and cyanotoxins play? The purification and control of the preparations is costly. In view of the rapidly growing demand, caution is advised. Each cleaning step reduces the yield. Those who have to compete, , will be reluctant to pass up this opportunity to save money.
The safest method is still chemical synthesis, which produces fairly stable cyanocobalamin without pseudovitamins and cyanotoxins. However, discerning customers prefer "natural" preparations, which are more expensive and unstable. In cloud cuckoo land, it is expected that the product should also be "free of genetic engineering". No problem: vitamin B12 is often produced using genetically modified microorganisms. As the metabolic pathway is complex, several genes in the bacteria have been modified. However, the vitamins produced in this way no longer contain GMOs and are therefore logically "GMO-free".
The human requirement is not even known. Nutritionists are once again making themselves important with fantasy figures. For children and adolescents, as well as for pregnant and breastfeeding women, the recommendations of the European Food Safety Authority (EFSA) were estimated on the basis of assumptions. (28) And what about the values for adults? "Experimental data from individuals with pernicious anaemia ... indicate that a daily intake of 1.5–2 μg of cobalamin is the minimum requirement for maintaining normal haematological status," according to the EFSA. This sounds reasonable, but it does not meet commercial needs.
So the EFSA is taking a new approach: "Based on ... the estimate of daily mandatory losses of cobalamin, the estimated cobalamin requirement is between 4 and 20 μg/day, .... The panel ... notes that an average requirement (AR) cannot be determined based on the limited data available." What follows from this? "The panel therefore sets an adequate intake (AI) for cobalamin of 4 μg/day for adults." To understand this correctly: in cases of acute deficiency, 2 micrograms per day are sufficient, but 4 µg are necessary for adequate supply.
Deutscher Apotheker Verlag is pleased for its readers and puts forward the DGE: "Adults should consume more vitamin B12, advises the German Nutrition Society (DGE). In 2022, it revised the reference values for vitamin B12 intake and increased them by a third."
But even that is not enough for a vitamin-obsessed business world: "It is currently assumed," doctors complain, "that the recommended daily dose may not be sufficient to ensure genomic stability and that a daily intake of 7 μg/day would be necessary for optimal plasma levels." (86) Capsules containing 5000 µg of so-called "B12" are already available on the market – vegan, GMO-free and from natural sources.
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