B12 in tea leaves

[Korn]

From http://www.ncbi.nlm.nih.gov/entrez/q...521&query_hl=1

Nutr Sci Vitaminol (Tokyo). 2004 Dec;50(6):438-40.
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Occurrence of vitamin B12 in green, blue, red, and black tea leaves.

Kittaka-Katsura H, Watanabe F, Nakano Y.

Department of Food and Nutrition, Kyoto Women's Untiversity, Kyoto 605-8501, Japan. kittaka@kyoto-wu.ac.jp

Vitamin B12 contents of green (0.046-0.263 and 0.125-0.535 microg/100 g dry weight), blue (0.068-0.081 and 0.525-0.528 microg/l00 g dry weight), red (0.061 and 0.663 microg/100 g dry weight), and black (0.104-0.859 and 0.305-1.20 microg/100 dry weight) tea leaves were obtained by intrinsic factor-chemiluminescence and microbiological methods, respectively. Although vitamin B12 was found in all tea leaves tested by both assay methods, the higher values by the microbiological method were not due to occurrence of both deoxyribosides and deoxynucleotides (known as an alkali-resistant factor), but may have been due to that of inactive corrinoid compounds for mammals in the tea leaves.

PMID: 15895521 [PubMed - in process]

[Korn]

Although vitamin B12 was found in all tea leaves tested by both assay methods, the higher values by the microbiological method were not due to occurrence of both deoxyribosides and deoxynucleotides (known as an alkali-resistant factor), but may have been due to that of inactive corrinoid compounds for mammals in the tea leaves.

PMID: 15895521 [PubMed - in process]

Here's a study which suggests that B12 found in certain ryuabo tea leaves are of the true/active type:
http://www.scirp.org/journal/PaperIn...9#.VAoV6mSSxTE

"Notably, Kittaka-Katsura et al. [10]demonstrated that administration of the Japanese black tea drink (B12 content, approximately 2.0 ng/100mL) considerably improves B12 status in B12-deficient rats. Considering these earlier observations and our present findings, we propose that Ryubao tea leaves containing significantly levels of B12 can be utilized as a source of vitamin B12 for vegetarians."
As usual...: Why study on rats and not humans?

"Our results indicate that Chinese black tea is usually not a good source of B12, although Ryubao tea leaves with the highest B12 content may be utilized as a source of this vitamin for vegetarians."




That's a surprising finding if only some of the ryubao leaves had relevant levels of active B12, isn't it? How would they find out which leaves that had active B12 and which leaves that didn't? The B12 amounts also seem very low, and the real question which remains is - how much tea would one need to drink in order to get a useful amount of active B12? And - if it's is assumed active, why not spend some extra time checking if it actually is active?

If "L" is short for litres (or have I misunderstood something?), I see this as Japanese humour: "B12 content in the tea drink prepared from the Ryubao tea leaf sample H was 0.8 ng/100mL of black tea. Therefore, consumption of approximately 300 L of this tea would provide the recommended dietary allowance for adults (2.4 μg/day) [14] [15] , although ingestion of such large quantities of tea on a daily basis is not recommended. "

[Risker]

how much tea would one need to drink in order to get a useful amount of active B12? And - if it's is assumed active, whu not spend some extra time checking if it actually ios active?

Exactly, think we're stepping in to the world of homeopathy here.