B12 compounds from Korean purple laver (Porphyra sp.) products: 51.7 mcg/100g

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J Agric Food Chem. 2009 Apr 8;57(7):2793-6.
Characterization of vitamin B12 compounds from Korean purple laver (Porphyra sp.) products.
Miyamoto E, Yabuta Y, Kwak CS, Enomoto T, Watanabe F.

Department of Health and Nutrition, Nagasaki International University, Sasebo 859-3298, Japan.

Abstract
Vitamin B(12) contents of various Korean purple laver products were determined with the microbiological vitamin B(12) assay method. Although a substantial amount (133.8 microg/100 g) of vitamin B(12) was found in dried purple laver, seasoned and toasted laver products contained lesser vitamin B(12) contents (about 51.7 microg/100 g). The decreased vitamin B(12) contents in the seasoned and toasted laver products, however, were not due to loss or destruction of vitamin B(12) during the toasting process. Silica gel 60 thin layer chromatography-bioautogram analysis indicated that all Korean laver products tested contain true vitamin B(12), but not inactive corrinoid compounds. In vitro gastrointestinal digestion experiments indicated that digestion rate of vitamin B(12) from the dried Korean purple laver was estimated to be 50% under pH 2.0 conditions (as a model of normal gastric function). These results suggest that Korean purple laver products would be excellent vitamin B(12) sources for humans, especially vegetarians.

PMID: 19256490 [PubMed - indexed for MEDLINE]

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Oooooooooooooooooooo!

Here's a somewhatsimilar study:

The nutritional status of iron, folate, and vitamin B-12 of Buddhist vegetarians PMID: 21393109 (2011)

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Nutritional status of iron, folate, and vitamin B-12 in vegetarians were assessed and compared with those of non- vegetarians in Korea. The vegetarian subjects were 54 Buddhist nuns who ate no animal source food except for dairy products. The non-vegetarians were divided into two groups: 31 Catholic nuns and 31 female college students. Three-day dietary records were completed, and the blood samples were collected for analyzing a complete blood count, and serum levels of ferritin, folate, and vitamin B-12. There was no difference in hemoglobin among the diet groups. The serum ferritin and hematocrit levels of vegetarians did not differ from that of non- vegetarian students with a high intake of animal source food but low intake of vitamin C, and the levels were lower than that of non-vegetarian Catholic nuns with a modest consumption of animal source food and a high intake of vitamin C. The serum vitamin B-12 levels of all subjects except one vegetarian and the serum folate levels of all subjects except one non-vegetarian student fell within a normal range. In vegetarians, there was a positive correlation between the vitamin C intake and serum ferritin levels as well as between the laver intake and serum vitamin B-12 levels. In order to achieve an optimal iron status, both an adequate amount of iron intake and its bioavailability should be considered. Sufficient intake of vegetables and fruits was reflected in adequate serum folate status. Korean laver can be a good source of vitamin B-12 for vegetarians.

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From the abstract, I can't see if the study mentions the bioavailability of this B12.

on the second study, since they ate dairy products, wouldn't seem to help on the laver one way or the other.