Vitamin B12 in Algae: Spirulina, Chlorella and Nori

Herbal B12 

Vitamin B12 in Algae: Spirulina, Chlorella and Nori

Vitamin B12 in algae: do algae like spirulina, chlorella and nori contain real vitamin B12 or B12 analogs? Is it possible to cover the B12 RDA with algae?

In this article, we will examine current knowledge about vitamin B12 content in algae, answering the following questions:

Content Questions

  1. What is the difference between real vitamin B12 and pseudo vitamin B12?
  2. Which algae contain actual vitamin B12?
  3. Can it be possible to cover your body’s B12 requirement through these algae?

Algae – a Herbal, Natural, Vegan Source of Vitamin B12?

Vitamin B12 is almost exclusively present in animal foods and is only found in traces at most in ordinary fruit and vegetables. A vegetarian or vegan diet can often provides no vitamin B12 sources, which is why research into a herbal source of vitamin B12 has been at the forefront of research for many years.

However, recently researchers hit the jackpot when delving underwater: algae has emerged as the sole, promising candidate for a botanical source of vitamin B12. The solution isn’t yet completely clear, as he subject is relatively complex and the research position has changed numerous times over the past decades, leading to many circulations of false reports.

Almost all algae previously tested has revealed so-called pseudo vitamin B12 instead of the real thing; an analog which is not only ineffective, but also potentially dangerous. Most researchers have consequently written off algae as a B12 source and recommend natural B12 supplements as a safe alternative. Despite all of this, there is an alga known as chlorella which could be the building block of a genuine vegan B12 supply.

Vitamin B12 in Algae: Real B12 or Vitamin B12 Analogs?

In order to properly understand the discussion about the B12 content of algae, it is important to first discuss so-called vitamin B12 analogs. B12 analogs, also known as pseudovitamin B12, are molecules which are so chemically similar to real vitamin B12 that they bond to the same transport molecule. However, they have no vitamin effect on the body whatsoever. This is very inconvenient, as only vitamin B12 which is bonded to this specific transport molecule can be used by the body.

If this is indeed the case and transport molecules are bonding to vitamin B12 analogs instead of real vitamin B12, then a B12 deficiency can exist even in spite of a very good vitamin B12 dietary supply, as the real vitamin B12 is simply not being transported around the body.

To read more about this topic, simply view our article vitamin B12 analogs.

Algae and Vitamin B12 Analogs

Vitamin B12 and its pseudo cousin are indeed so similar that conventional testing methods cannot differentiate between them. Only complex test procedures can make a clear distinction between the two. This has led to confusion regarding herbal sources of vitamin B12 in the past, as vitamin B12 analogs have often been falsely identified as vitamin B12.

When assessing a source of B12, it is always important to keep in mind the relationship between vitamin B12 and pseudovitamin B12 and to compare the real B12 content in the source against the level of vitamin B12 analogs. In order to ensure a positive effect, sources should ideally only contain real vitamin B12, but at the very least, the genuine vitamin B12 should significantly outweigh the B12 analogs.

If the level of real B12 is heavily outweighed by the level of pseudo vitamin B12, the chances of a B12 deficiency increase significantly, as the analogs bond to the necessary transport molecules, ensuring that the body cannot use the real vitamin B12.

Vitamin B12 Content of Algae

As we will discover shortly, there are really only two types of algae – chlorella and more recently nori, which question the possibility of a herbal vitamin B12 supply. However, both have one significant weakness, in that the vitamin B12 content found in them is not produced by the algae itself, but rather by microorganisms which live within the plant or underground.

The B12 content thus depends massively on the growing conditions and availability of these microorganisms; no definitive statement can be made over the exact vitamin B12 content of these algae. Even in the same location, levels can rise and fall year upon year quite drastically.

At present, the Vegan Society doesn’t consider algae such as these to be a herbal B12 source and instead advises taking vitamin B12 supplements which contain vitamin B12 in its natural form.

Which Algae Contain Vitamin B12?

Before we examine each individual algae in detail, here is a brief overview of the candidates currently being discussed.

AFA~ 30~ 570negative
Nori (red alga)highly variablehighly variableunclear
Chlorella (naturally produced)~ 100 µg< 10 µgpositive
Chlorella (artificially grown, fermented)neutral

When comparing algae in this table, it is worth remembering that the values given here are an average – the actual content can vary significantly from product to product and harvest to harvest.


  • Most algae don’t contain actual vitamin B12, just dangerous vitamin B12 analogs
  • The only alga with a verified B12 content is bio chlorella
  • The only surefire way to guarantee a B12 supply is by taking vitamin B12 supplements which use natural B12 form

Spirulina: Not a Vitamin B12 Source

For a long time, spirulina was considered a vitamin B12 source. The vitamin B12 level which it showed when tested by conventional methods has been disproven by recent testing, which proved it to simply be vitamin B12 analogs.1-3

In actual fact, the vitamin B12 content has been measured to total just 30%, a very low amount compared to the level of pseudo-vitamin B12.4,5

As expected, taking spirulina significantly worsened the B12 status of a research group in a study carried out, which found that the B12 analogs impaired the absorption rate of genuine vitamin B12.Vegans, vegetarians and people with vitamin B12 absorption difficulties should thus steer clear of spirulina products.

It is also not recommended to take spirulina alongside vitamin B12 supplements, as the pseudo-B12 in the spirulina can hinder absorption.

Spirulina products are no longer allowed to be advertised as vitamin B12 sources.7

AFA Alga (Aphanizomenon flos-aquae)

The AFA alga has very similar properties to spirulina; its previously measured vitamin B12 content has now been proven to be pseudovitamin B12 and this alga is now no longer considered a supplier of vitamin B12.8

One study on AFA, which is still frequently cited, attempted to measure the effect of the alga through testing vitamin B12 levels in serum and homocysteine levels. Both of these are unsuitable, as the serum test cannot differentiate between B12 and its analog, whilst the homocysteine test is also influenced by levels of folate and vitamin B6.Exact chemical determinants can show that this alga simply contains useless pseudovitamin B12.

Nori – Still Debated as a Vitamin B12 Source

One candidate which still remains controversial is the red alga nori (porphyra). Some studies have identified its B12 content as an analog,whilst others have come to the conclusion that the vitamin B12 which is measured in the fresh algae is destroyed during the drying process. It was also possible to indicate that eating dried nori actually worsened the vitamin B12 status in the body.10

On the other side of the coin, some studies have shown that nori contains large quantities of genuine vitamin B1211,12 and have shown it to have a clear biological effect when tested on rats.13

The aforementioned results regarding nori are still commonly disputed and have mostly been interpreted as indication that, since the vitamin B12 and analog content varies so much from test to test, no clear statement can be made on nori as a vitamin B12 source.

Using this information, nori cannot be considered a reliable vitamin B12 source, because it is not possible for the consumer to check the vitamin B12 content of each specific purchase.

Chlorella – the Best Candidate at Present

Out of all the potential herbal B12 sources, chlorella is the most promising at present.

However, there are also contradictory studies on this alga. The first american study, carried out in 1968, couldn’t prove any B12 whatsoever,14 but current studies show a pleasingly high B12 content, with low levels of vitamin B12 analogs at the same time.15,16

One theory for an explanation of this difference is that many commercial spirulina products are grown under sterile conditions, which is not conducive to the production of microorganisms necessary for vitamin B12 development. Others assume that the first study simply failed on account of its now outdated testing methods.

At present, there is no evidence to suggest that chlorella can cure a vitamin B12 deficiency, because no such study has been carried out. This would require research in order to scientifically prove sufficient vitamin B12 levels in chlorella. Despite this, chlorella certainly seems to be the standout candidate for a potential vegan source of vitamin B12.

Chlorella: Vitamin B12 Content

The vitamin B12 content of chlorella does vary slightly across studies. The average content can be considered 80 – 100 µg per 100g according to current studies.

In consideration of the absorption mechanism of vitamin B12, three grams of chlorella (the equivalent of a teaspoon or roughly six tablets) should be taken in the morning and evening, in order to optimize chances of covering the body’s daily requirement.

This is however a significantly more expensive alternative to vitamin B12 supplements. Chlorella products are around five times the price of conventional vitamin B12 supplements, but they do also include other important nutrients such as protein, vitamin D and chlorophyll.

Price comparison between chlorella and B12 supplements

Product*Total B12 ContentPrice
B12 capsules50,000 µgfrom 15 Euro
Chlorella powder (Bio)10,000 µgfrom 16 Euro
Chlorella pills (Bio)12,000 µgfrom 20 Euro

*The cheapest product available was used for comparison

Who is Algae Suited for as a Vitamin B12 Source?

The B12 content of chlorella might be very high for a plant, but it is still considered quite low overall. A supply of vitamin B12 from this alga alone will only suffice if your health and lifestyle matches the following description:

  • Very good health
  • Optimal absorption rate
  • Very low requirement (no stress, no disease)
  • Several doses of chlorella per day

A sensible option would be to take chlorella alongside a vitamin B12 supplement, so that the chlorella isn’t being relied upon to cover the daily requirement alone. In addition to these two, other herbal sources can be consumed to add further small doses of vitamin B12, such as juices or special vegan products.

Herbal Vitamin B12

Readers who are desperate for a herbal, natural source of vitamin B12 can consider chlorella to be the best option currently available. Whether it better for you than vitamin B12 supplements, however, is still a matter of debate. Provided that supplements contain natural forms of hydroxocobalamin and methylcobalamin, they can be considered identical to natural sources, even if the active ingredients have been chemically isolated.

The low content of vitamin B12 in chlorella unfortunately makes it impractical as the sole source of vitamin B12 in many cases. Even slight absorption difficulties require a relatively large amount of vitamin B12 to correct.

Algae are best used as part of a diet which contains several sources of vitamin B12, such as enriched vegan products. In doing this, the body’s B12 intake can be spread evenly over the course of day, allowing the absorption mechanism for vitamin B12, the intrinsic factor, to work optimally; an important factor, as it can only absorb around 1.5 µg per dose.


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3H. van den Berg, L. Brandson, B. J. Sinkeldam: Vitamin B12 content and bioavailability of spirulina and nori in rats. Journal of Nutritional Biochemistry, 1991, 2(6), 314-318
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9Baroni, Luciana, et al. Effect of a Klamath algae product (“AFA-B12”) on blood levels of vitamin B12 and homocysteine in vegan subjects: a pilot study. International journal for vitamin and nutrition research, 2009, 79. Jg., Nr. 2, S. 117-123.
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13Takenaka S, Sugiyama S, Ebara S, Miyamoto E, Abe K, Tamura Y, Watanabe F, Tsuyama S, Nakano Y. Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status. Br J Nutr. 2001 Jun;85(6):699-703. PubMed PMID: 11430774.
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