B12 supplementation

Many people – including doctors – have no idea what supplementing this vitamin without the aid of injections should look like. I’m often asked about this, it’s worth having it all in one place.

By way of introduction, some interesting facts.

No animal can synthesize this vitamin in its body, and no plant contains it, although there are reports that marine algae can be a source of it – generally thought to contain mostly inactive analogs, but studies of people eating large amounts of sea greens have shown that they are not deficient:


I suppose, however, that it is not so much about the production in the algae themselves, but simply about the bacteria that either live in symbiosis with them, or simply find themselves on the surface of these plants.

It is practically impossible to maintain adequate levels of this vitamin on a vegetarian diet, let alone a vegan one. A vegan woman once told me that she had good results – she did, but then it turned out that someone simply put supplements in her food. On such diets, levels will slowly, inexorably drop until unpleasant symptoms begin to appear. This lasts long enough that people simply don’t associate it with themselves, or they think it’s normal because of aging. The reserves in the body can last up to 15 years.

An attentive reader will notice a contradiction here – how is it, since no plant contains this vitamin, and animal organisms are not able to produce it, how come herbivores are able to survive without pills? The answer is very simple – exactly how the vegetarian communities of our ancestors survived, and the vegetarian communities today in poor countries like India.

B12 is produced by bacteria, on top of being a fairly common metabolic product. In practice, dirty water, dirty food, and – or rather, primarily – insects and small invertebrates such as snails are sufficient sources. Herbivorous monkeys, when they are in captivity and given “sterile” food, begin to show deficiency symptoms after a while.

In theory, it is possible to eat a B12 sufficient diet without meat, milk and eggs, but in practice it would be prohibitively expensive, time-consuming and above all unhealthy. Quite quickly we would end up with infections of the digestive tract, as well as growing a lot of parasites.

A bit of assimilation theory. In order for this vitamin to be digested, it has to combine with a certain substance in the stomach (lack of its production is one of the most common causes of deficiencies). This is why the one produced by bacteria in the gut is useless to us. But this substance is very little, only enough for 1 mcg (about half of what we should eat each day). This means that no matter how much we eat in a supplement – whether it is 1 mcg or 10,000 mcg, we will assimilate the same amount. A supplement that contains 500% of your needs won’t really be any different from one that contains 100% – both will give about 50%.

But here is something that can help us – the passive penetration of B12 through the intestinal membranes. About 1% of what we ingest will be absorbed this way, even if our stomach does not produce the factor responsible for enabling digestion at all. In practice, this means that by swallowing a supplement that has 10,000% of the requirement, we are providing 150% – the amount that will combine in the stomach, and 1/100th of the rest.

Now about the deficiency itself. Usually when we detect it, it’s already very bad – if you’re diagnosed with blood changes, you’ve probably had time to develop irreversible brain changes. Anemia is one of the last stages, so it is a crime to say that someone is not deficient because they are not anemic.

It is safe to assume that a person diagnosed with deficiency has depleted B12 stores in the liver and cells. The human body stores about 2500 mcg of B12, so it’s safe to assume that we’re aiming to replenish about 2000 mcg to restore full function, as well as to build up reserves to maintain health during, for example, intestinal disease, during which consumption is very high.

It is difficult to tell how much of the ingested B12 is stored, and how much will be immediately used up or simply peed out. However, one can rely on the tripling rule for safety – that is, we aim to get about 6,000 mcg of B12 into our blood, appropriately timed to give the body a chance to slowly store it.

It’s time to combine the information given above into a logical whole. We want to provide 6000 mcg of a substance that we assimilate only 1% of. This means that we need to consume 600,000 mcg, 600 mg in supplements, with a very large improvement expected after “only” 200 mg.

Now let’s look at what you can buy at the pharmacy. If one tries to supplement the deficiency with popular 10 mcg tablets, the full effect will be achieved after eating 60,000 pills. If one buys “very strong” tablets containing 500 mcg, then “only” 1,200 of them will be enough, but after only 400, a very big improvement will be visible.

You can buy capsules that contain 5000 mcg – and these should be used. 100 such tablets, spread over several months, should be enough to make up for the deficiency and create a sufficient supply to survive states of increased demand.

Now a word about the different forms.

Very often you can read that the methyl~ or adenosyl~ forms are much better absorbed, that our body will not use ordinary cyanocobalamin as it can use the “active” ones. The source of this myth is that inside cells we have just these forms – methyl, adenosyl and hydroxy. On the face of it, it is logical that by providing adenosylcobalamin, for example, we are making our body’s task easier.

However, the truth is different – these vitamins are broken down into their individual components before they enter the cell, and only inside the cell does our body produce the methyl and adenosyl forms:



In other words, it makes virtually no difference which form we choose. Methylcobalamin may turn out to be a source of methyl groups, I would add, nightmarishly expensive compared to betaine, for example, and this may explain the improvement felt by some people over regular cyanocobalamin. I am also not sure if there is no mistake in the above studies – it is possible that the adenosyl form is destroyed before entering the cell, but perhaps it will be better stored in the liver – in that form it is found there.

Finally, it’s not possible to stay healthy on a vegan diet by taking very large doses of supplements e.g. once a month. To avoid deficiency, B12 needs to be supplemented regularly with smaller doses.