Seaweed and Vitamin B12

A paper has just been published in Advances in Food and Nutrition Research that claims seaweeds are a good source of vitamin B12 for vegans (1). The author does not provide any new information, but rather relies on a number of studies that have measured the B12 analogue content of various seaweeds (see B12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods for an analysis of these studies).


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To date, no study has shown any seaweed to improve vitamin B12 status, although two studies showed that spirulina (2) and nori (2, 3) were not able to do so. So it is rather premature, to say the least, to say that any seaweed is a “good” source of vitamin B12, and unfortunate that someone would publish that opinion in a peer-reviewed journal.

References

1. Skrovánková S. Seaweed vitamins as nutraceuticals. Adv Food Nutr Res. 2011;64:357-69.   |   Link

2. Dagnelie PC, van Staveren WA, van den Berg H. Vitamin B-12 from algae appears not to be bioavailable. Am J Clin Nutr. 1991;53:695-7.   |   Link

3. Yamada K, Yamada Y, Fukuda M, Yamada S. Bioavailability of dried asakusanori (porphyra tenera) as a source of Cobalamin (Vitamin B12). Int J Vitam Nutr Res. 1999 Nov;69(6):412-8. Yamada K, Yamada Y, Fukuda M, Yamada S. Bioavailability of dried asakusanori (porphyra tenera) as a source of Cobalamin (Vitamin B12). Int J Vitam Nutr Res. 1999 Nov;69(6):412-8.   |   Link

5 Responses to “Seaweed and Vitamin B12”

  1. Paul Says:

    I agree with Jack on this. One wonders what goes on in some ‘peer-reviewed’ journals these days.

  2. Mike Says:

    If algae is full of analogues, how come fish ends up being a good source of B12? It was able to improve macrocytic anemia in the Dagnelie study for example.

  3. Jack Norris RD Says:

    Mike,

    Fish, and other mammals, are able to select the active B12 from the inactive once it’s in their system and so most of the inactive analogues get weeded out.

  4. Mike Says:

    If that was true, then humans would be able to obtain B12 from things like spirulina and nori. But we know they can’t because the analogues block the genuine B12 from being absorbed. I’m convinced that other animals have a unique filtration system that humans do not.

  5. Jack Norris RD Says:

    Mike,

    It’s not an all or nothing thing and humans do have the system that separates the active from the inactive B12 for most analogues. I’m actually not sure how fish get most of their vitamin B12 — whether it be bacteria in their gut or from the water they swallow or from food (plants or animals). And I wouldn’t say that we know for sure that no seaweed can be a source of vitamin B12 — particularly if it happens to be contaminated by b12-producing bacteria. But at this time, there’s no way to say “take X amount of seaweed X” and your homocysteine levels will be healthy and you will not develop B12 deficiency.

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