b12 y algas

[Mad doctor]

A raíz de una citación bibliográfica de nuestro estimado compañero Veganauta, he navegado por las bases de datos bibliográficas y me he encontrado con algunas buenas noticias.

Los artículos son de 1999, por lo que no entiendo porqué no están más extendidos entre los asesores nutricionales del sector vegetariano.

Esto hace que deba profundizar más en artículos más recientes para ver cómo está el tema, e iré actualizando en este hilo.

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

Department of Liberal Arts and Sciences, School of Health Sciences, Sapporo Medical University, Japan.

We have already reported that raw nori (Porphyra tenera) contains cobalamin (Cbl) but not Cbl analogues (J. Nutr. Sci. Vitaminol., 42, 497, 1996). It seems, therefore, that it is an excellent natural vegetable source of Cbl. On the other hand, it has been reported that the Cbl nutritional status of vegetarian children deteriorated as estimated by the hematological index, mean corpuscular volume (MCV), after they had dried nori as a source of Cbl. Such a discrepancy between raw and dried nori as a source of Cbl led us to investigate whether Cbl in dried nori had different properties from that in raw nori. We found that contents of Cbl homologues determined by a bioassay method in both raw and dried nori were similar. The urinary methylmalonic acid excretion increased when human female volunteers were given 40 g of dried nori daily during the test period. On the other hand, the urinary methylmalonic acid excretion did not change when volunteers were daily given 320 g of raw nori, which was equivalent to 40 g of the dried one on the basis of dehydrated weight, during the test period. By paper chromatography, 65% of the Cbl homologues were found to be comprised of Cbl analogues in dried nori, while 73% of the Cbl homologues in the raw nori were genuine Cbl. These results were confirmed by the finding that the bioassay method gave higher values for Cbl homologues than those obtained by a competitive binding assay method using an intrinsic factor as a Cbl-binding protein. Our present data demonstrated that Cbl in raw nori can be changed into harmful Cbl analogues by the drying process.

Según éste, parece ser que el alga nori crudo es una buena fuente de b12, pero que durante el proceso de secado aumenta el número de análogos, lo que reduce su biodisponibilidad. Los datos han sido obtenidos en humanos, y analizando el ácido metilmalónico, por lo que me parecen fiables. Hablan de 320 gramos diarios de Nori crudo, una cantidad elevada la verdad, tendríamos que ver cuál es la cantidad de b12 por cada 100 gramos para establecer cuál sería la cantidad óptima diaria de Nori cruda que cubriría las fuentes de b12.

Sin embargo nos topamos con esto.

J Agric Food Chem. 1999 Jun;47(6):2341-3.Click here to read Links
Dried green and purple lavers (Nori) contain substantial amounts of biologically active vitamin B(12) but less of dietary iodine relative to other edible seaweeds.
Watanabe F, Takenaka S, Katsura H, Masumder SA, Abe K, Tamura Y, Nakano Y.

Department of Health Science, Kochi Women's University, Japan. watanabe@cc.kochi-wu.ac.jp

Vitamin B(12) concentrations of dried green (Enteromorpha sp.) and purple (Porphyra sp.) lavers (nori) were determined by both Lactobacillus leichmannii ATCC 7830 microbiological and intrinsic factor chemiluminescence methods. The values determined by using the microbiological method (63.58 +/- 2.90 and 32.26 +/- 1.61 microg/100 g of dry weight) were identical to those found by using the chemiluminescence method (69.20 +/- 2.21 and 25.07 +/- 0.54 microg/100 g of dry weight) in both dried green and purple lavers, respectively. A silica gel 60 thin-layer chromatography of both laver extracts shows that non-coenzyme forms (hydroxo and cyano forms) of vitamin B(12) predominate in both dried lavers. The dried lavers contained lesser amounts of dietary iodine ( approximately 4-6 mg/100 g of dry weight) relative to other seaweeds, suggesting that excessive intake of the dried lavers is unlikely to result in harmful intake of dietary iodine. These results indicate that the dried lavers (nori) are the most excellent source of vitamin B(12) among edible seaweeds, especially for strict vegetarians.

En este artículo publicado un par de meses antes, parece que llegan a una conclusión completamente contrapuesta (bienvenidos al maravilloso mundo de la ciencia!). Según este la estabilidad de la b12 es buena en el alga deshidratada, y dado que contiene menos iodo, la hace más idónea aún que la cruda como fuente de b12. Vemos una media de 30 ug/100g de b12 en alga seca, de modo que 10 gramos de alga seca proporcionaría 3 ug (una dosis diaria recomendada).

Un estudio más reciente con ratas, demuestra también su biodisponibilidad, pero claro, es con ratas, y esto poco nos puede decir para el ser humano:

Br J Nutr. 2001 Jun;85(6):699-703.Click here to read Links
Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status.
Takenaka S, Sugiyama S, Ebara S, Miyamoto E, Abe K, Tamura Y, Watanabe F, Tsuyama S, Nakano Y.

Laboratory of Nutrition and Food Science, Hagoromo-gakuen College, Sakai 592-8344, Japan. takenaka@vet.osakafu-u.ac.jp

To clarify the bioavailability of vitamin B12 in lyophylized purple laver (nori; Porphyra yezoensis), total vitamin B12 and vitamin B12 analogue contents in the laver were determined, and the effects of feeding the laver to vitamin B12-deficient rats were investigated. The amount of total vitamin B12 in the dried purple laver was estimated to be 54.5 and 58.6 (se 5.3 and 7.5 respectively) microg/100 g dry weight by Lactobacillus bioassay and chemiluminescent assay with hog intrinsic factor respectively. The purple laver contained five types of biologically active vitamin B12 compounds (cyano-, hydroxo-, sulfito-, adenosyl- and methylcobalamin), in which the vitamin B12 coezymes (adenosyl- and methylcobalamin) comprised about 60 % of the total vitamin B12. When 9-week-old vitamin B12-deficient rats, which excreted substantial amounts of methylmalonic acid (71.7(se 20.2) micromol/d) in urine, were fed the diet supplemented with dried purple laver (10 microg/kg diet) for 20 d, urinary methylmalonic acid excretion (as an index of vitamin B12 deficiency) became undetectable and hepatic vitamin B12 (especially adenosylcobalamin) levels were significantly increased. These results indicate that vitamin B12 in dried purple laver is bioavailable to rats.

Éste otro más reciente, de 2002, recalca la inutilidad de la Espirulina, pero si incluye como fuente fiable la Chlorella. De nuevo el punto flaco que está obtenido a partir de resultados obtenidos en ratas, y poco extrapolable a humanos, aunque el artículo se empeñe en usar el término "mamíferos" para incluir a todo el filo, por un resultado obtenido en ratas.

J Nutr Sci Vitaminol (Tokyo). 2002 Oct;48(5):325-31.Links
Characterization and bioavailability of vitamin B12-compounds from edible algae.
Watanabe F, Takenaka S, Kittaka-Katsura H, Ebara S, Miyamoto E.

Department of Health Science, Kochi Women's University, Kochi 780-8515, Japan. watanabe@cc.kochi-wu.ac.jp

Substantial amounts of vitamin B12 were found in some edible algae (green and purple lavers) and algal health food (chlorella and spirulina tablets) using the Lactobacillus delbrueckii subsp. lactis ATCC7830 microbiological assay method. Corrinoid-compounds were purified and characterized from these algae to clarify the chemical properties and bioavailability of the algal vitamin B12. True vitamin B12 is the predominate cobamide of green and purple lavers and chlorella tablets. Feeding the purple laver to vitamin B12-deficient rats significantly improved the vitamin B12 status. The results suggest that algal vitamin B12 is a bioavailable source for mammals. Pseudovitamin B12 (an inactive corrinoid) predominated in the spirulina tablets, which are not suitable for use as a vitamin B12 source, especially for vegetarians. algal health food, bioavailability, cobalamin, edible algae, vitamin B12

[Mad doctor]

En esta revisión bibliográfica bastante reciente, 2007 (revisión completa: http://www.ebmonline.org/cgi/reprint/232/10/1266)

Exp Biol Med (Maywood). 2007 Nov;232(10):1266-74.Click here to read Links
Vitamin B12 sources and bioavailability.
Watanabe F.

School of Agricultural, Biological and Environmental Sciences, Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan. watanabe@muses.tottori-u.ac.jp

The usual dietary sources of vitamin B(12) are animal foods, meat, milk, egg, fish, and shellfish. As the intrinsic factor-mediated intestinal absorption system is estimated to be saturated at about 1.5-2.0 microg per meal under physiologic conditions, vitamin B(12) bioavailability significantly decreases with increasing intake of vitamin B(12) per meal. The bioavailability of vitamin B(12) in healthy humans from fish meat, sheep meat, and chicken meat averaged 42%, 56%-89%, and 61%-66%, respectively. Vitamin B(12) in eggs seems to be poorly absorbed (< 9%) relative to other animal food products. In the Dietary Reference Intakes in the United States and Japan, it is assumed that 50% of dietary vitamin B(12) is absorbed by healthy adults with normal gastro-intestinal function. Some plant foods, dried green and purple lavers (nori) contain substantial amounts of vitamin B(12), although other edible algae contained none or only traces of vitamin B(12). Most of the edible blue-green algae (cyanobacteria) used for human supplements predominantly contain pseudovitamin B(12), which is inactive in humans. The edible cyanobacteria are not suitable for use as vitamin B(12) sources, especially in vegans. Fortified breakfast cereals are a particularly valuable source of vitamin B(12) for vegans and elderly people. Production of some vitamin B(12)-enriched vegetables is also being devised.

En esta revisión, se incluye este dato:

A nutritional analysis for the dietary food intake and serum vitamin B12 level of a group of six vegan children aged 7 to 14 who had been living on a vegan diet including brown rice for 4 to 10 years suggests that consumption of nori may keep vegans from suffering vitamin B12 deficiency (59). Rauma et al. (60) also reported that vegans consuming nori and/or chlorella had a serum vitamin B12 concentration twice as high as those not consuming these algae.

El nivel de b12 en seis niños veganos de 7 a 14 años sugiere que el consumo de nori evita los síntomas de la deficiencia de b12 en niños. Los veganos que consumen nori y chlorella tienen una concentración de b12 el doble que en aquellos que no la consumen.


----


Parece haber consenso en que las especies Enteromorpha sp. y Porphyra sp. son fuentes fiables de b12, aunque no hay consenso entre las formas crudas y secas. También parece haber consenso con Chlorella. El consenso importante es EVITAR LA ESPIRULINA.


Seguiré investigando y actualizando el post.

[Tito Chinchan]

El consenso importante es EVITAR LA ESPIRULINA.

Ya me lo decía mi madre "Niño, no te toques tanto la (es)pirulina, que se te va a caer al suelo"

Qué maremagnum de información algar. Lo malo es que luego no hay manera de encontrar algas tiernas en ningún sitio. Tras mucho años las ví creo que en el Hipercor, pero había muy poquitas latas.

Buen aporte, Mad Max Doctor.

Besitos.

[aaaxxx]

Yo tomo espirulina hace años y ya llega un punto que no sé ni porqué. La tomo desde mucho antes de ser vegana... y llegado este punto pregunto... qué de buena me aporta la espirulina?

[Mad doctor]

... qué de buena me aporta la espirulina?

Bueno más bien poco, malo bastante.

Para uso saciante, mejor usar comprimidos de fucus, y para más natural Fucus deshidratado.

[JustVegetal]

Bueno más bien poco, malo bastante.

Para uso saciante, mejor usar comprimidos de fucus, y para más natural Fucus deshidratado.

¿Qué aporta de malo la espirulina?

[Mad doctor]

¿Qué aporta de malo la espirulina?

Pues que mete mucho análogo de b12, y compite con la absorción de la buena (la activa para humanos) y puede llevar a derivar en anemia.

[JustVegetal]

El tema de la B12 es que es tremendo, pero no solo en veganos, este fin de semana estuve hablando con un médico que me dijo que piensan que la mayoría de B12 ingerida vía digestiva tampoco llega a asimilarse, y recomendaba las que se ponen debajo de la lengua, otras que hay en spray, o directamente inyectarla por vía intramuscular, en dosis de 1000 microunidades, además decía que toda la gente que tenga problemas digestivos, intolerancias, celíacos, deficiencias pancreáticas, etc y los mayores de 50 años, eran totalmente susceptibles de carecer de B12, incluso la relacionaba directamente cn el alzheimer y otras patologías muy graves.

[sujal]

Pero... ¿existe eso que llaman B12? tanto meneo se le está dando a esta escurridiza vitamina que ya dudo de ella. ¿No mutará como los virus?

[Mad doctor]

La b12 es el nuevo opio del pueblo...jejeje, así nos tienen controlados, llegará el día que compremos medio gramo de b12 a 60 euros en el bar de la esquina y adulterada...