54.5-58.6 microg/100 g in Nori (dry weight) [PMID: 11430774]
At PubMed there is an article documenting that dried purple laver (nori) is contains vitamin B12 that is bioavailable - at least for rats.
Some claim that nori is a useful, natural, plant based B12 source for humans, other claims the opposite. What do you think? And why didn't they try this on humans instead?
Here is the article:
"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.
PMID: 11430774 [PubMed - indexed for MEDLINE]"
http://store1.yimg.com/I/organickingdom_1789_544810
Re: Nori, MMA, B12 and... rats!
From http://www.jsbba.or.jp/e/e_05/bbb6412e.html
Quote:
Characterization of a Vitamin B12 Compound in the Edible Purple Laver,
Porphyra yezoensis
Fumio WATANABE,1,? Shigeo TAKENAKA,2,? Hiromi KATSURA,3 Emi MIYAMOTO,1
Katsuo ABE,1 Yoshiyuki TAMURA,2 Toshiyuki NAKATSUKA,4 and Yoshihisa NAKANO5
1Department of Health Science, Kochi Women?s University, Kochi 780-8515, Japan
2Laboratory of Nutrition and Food Science, Hagoromo-gakuen College, Sakai 592-8344, Japan
3Department of Health Science, Hiroshima Women?s University, Hiroshima,734-8558, Japan
4Department of Food Science, Shimane Women?s College, Matsue 690-0044, Japan
5Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai 599-8531, Japan
Received June 6, 2000; Accepted July 6, 2000
The edible purple laver, Porphyra yezoensis, contained 51.49±1.51 ?g of vitamin B12 compounds per 100 g dry weight of the laver (mean±SEM, n=4). A vitamin B12 compound was purified from the lyophilized purple laver and partially characterized. The silica gel 60 TLC and reversed-phase HPLC patterns of the purified pink-colored compound were identical to those of authentic vitamin B12, but not to those of vitamin B12 analogues inactive for humans.
Key words: vitamin B12; methylcobalamin; purple laver; Porphyra yezoensis; intrinsic factor
(The same material is also posted here: http://grande.nal.usda.gov/ibids/ind...&therow=133674 )
Re: 54.5-58.6 microg/100 g in Nori (dry weight)
Here's a study comparing the levels of 'true' B12 (genuine cobalamin) with B12 analogues in fresh and dried Nori:
http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus (1999)
Quote:
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.
PMID: 10642899 [PubMed - indexed for MEDLINE]
Re: 54.5-58.6 microg/100 g in Nori (dry weight)
Here's another study of B12 in nori:
Occurrence of Coenzyme Forms of Vitamin B12 in a Cultured Purple Laver (Porphyla yezoensis) PMID: 14646215
Quote:
Porphyra yezoensis (Susabinori, an edible purple laver), which was cultured aseptically for 12 weeks and then lyophilized, contained 50.+-.2 .MU.g/g of vitamin B12 per 100 g dry weight. Coenzyme forms of vitamin B12 (about 60% of the total vitamin B12) were found in the cultured purple laver aseptically, which may have the ability to biosynthesize the coenzymes.
So - according to these tests, nori actually contain bioavailable B12.
Nori is one of the only (the only?) sea plants that are tested using the gold standard of lowering MMA levels in humans, and while the studies on rats (sorry, rats) showed that nori significantly increased the B12 levels but this was also "demonstrated by the elimination of methylmalonic acid from the urine".
The question is - do we want B12 levels to continuously increase? If we would, we would maybe have a level of 200 pmol today, 400 pmol next year, 1500 pmol in a few years etc. I'd say that this is NOT what we want (unless we are talking about treating a deficiency, in which case, normal amounts of B12 shouldn't be used anyway.)
Human breast milk contains B12, and - unless the mother is B12 deficient - this breast milk will provide the babies with the B12 they need. When the baby isn't breastfed anymore, it needs to get B12 from other sources (some will disagree and say that in a healthy person, we'll get the B12 we need from recycling and B12 production in the mouth, but I'll assume that this is wrong for now). So - a healthy amount of B12 is an amount that will ensure that your B12 levels will remain on a healthy level; not a pmol-increase from year to year, and no deficiency.
Since not all B12 is recycled (this is what almost everybody agree in), we lose some B12 every day. In other words, a B12 source that can keep our B12 and homocysteine / MMA levels on a stable, healthy level (read: make sure that the levels don't decrease or increase) is what we're looking for.
Again - in this context it's important to understand the difference between a normal, regular intake of B12 for healthy people on one side, and a therapeutic dose meant to treat a B12 deficiency on the other side. It doesn't make sense to expect that a B12 amount meant for normal, daily/weekly maintenance of the levels would have the same effect as a therapeutic amount of B12, which purpose is to increase the B12 levels. What a healthy person want is keeping the healthy levels where they are.
Still - some of the anti-vegan 'experts' out there (and a few of their vegan friends) use the fact that Nori only keeps the MMA levels 'the same' against these products, based on a very strange kind of logic, which doesn't differentiate between B12 in food (meant to maintain healthy levels) and therapeutic amounts if B12 meant to treat B12 deficiency. No doctor I'm aware of would treat B12 deficiency by giving the deficient patient the same amount of B12 that he would have consumed in a non-deficient state. This is simple maths: if you use $100 a day, and earn $100 day, you're situation is stable. If you have too little money, say - if you owe someone $1000, you need to earn more than $100 for a while in order to get in balance. You can't heal your 'broke-ness' with earning as much as you normally would - you need some extra money. Still, some of the supplement fanatics out there claim that foods that can't to correct B12 deficiency consistently, should not be relied upon. But who on this earth are treating a deficiency of any kind with amounts meant for people without a deficiency?
It is commonly thought that humans need a B12 intake of 2-3 mcg/day, treating a B12 deficiency is often used with much higher amounts of B12, like 1000 mcg/day or 2000 mcg/day. To state that normal food with normal B12 levels can't be relied upon as food because it doesn't offer the same amount of B12 that is required for treatment of severe B12 deficiencies just doesn't make sense. I know of only one vegan site claiming this, but unfortunately it's a site that is often cited.
If we need eg. 2 or 3 mcg B12 pr. day in order not to have our B12 levels reduced, and we - by eating certain amounts of certain seaweeds or other plants that will help us remaining at a healthy level (read: food that will not increase or decrease B12 levels in a healthy person with healthy B12 levels), we should be happy, because what we want is 'no change'.
These same 'experts' admit that the nori in these tests 'didn't harm B12 status', which shows the they don't contain those famous analogues that apparently kill the B12 thats already in the system.
Now, before anyone says that B12 analogues don't kill the B12 that already is consumed, but it blocks other, true B12 from being absorbed, I agree that this is a relevant comment, but the funny thing is that those who claim that the presence of B12 analogues always is harmful because it blocks absorption of genuine B12 from food other food, are the same people who claim that there are no genuine B12 in plant food, so why would they worry? Maybe they would worry that eating anything containing B12 analogues (like tamari/soy sauce) would block the intake of B12 from supplements, but supplements have also been found to continue B12 analogues. Plus, if eg. soy sauce would be that harmful (because the fermentation creates B12 analogues), and if B12 deficiency always would be as harmful as some people claim, wouldn't all Chinese people already be dead?? They eat soy sauce every day! :)
Don't get me wrong; vegans are more likely to develop B12 deficiency than non-vegans, and we don't want to take any risks with ourselves or our kids. We should take our B12 levels at least as seriously as meat eaters take their levels of eg. folate, antioxidants or phytosterols. We don't want to be 'as healthy' as meat eaters, we want to be a lot healthier (most of us probably are).
On another site, someone wrote something like "when i was guzzling big macs i didn't care or get my levels checked... i just felt crap, that was all i knew"... and still, many vegans who feel better than ever, worry more about their levels than when they ate junk food only and felt horrible. And - in a way we should, because we are main advertisements for going vegan out there... let's not just take it too far.
Sorry for the short post. I'll post more later. :)
Re: 54.5-58.6 microg/100 g in Nori (dry weight)
I haven't seen this one posted, sorry if I duplicate.
http://pubs.acs.org/cgi-bin/abstract...jf981065c.html
Quote:
Dried Green and Purple Lavers (Nori) Contain Substantial Amounts of Biologically Active Vitamin B12 but Less of Dietary Iodine Relative to Other Edible Seaweeds
Vitamin B12 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 mcg/100 g of dry weight) were identical to those found by using the chemiluminescence method (69.20 ± 2.21 and 25.07 ± 0.54 mcg/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 B12 predominate in both dried lavers. The dried lavers contained lesser amounts of dietary iodine (~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 B12 among edible seaweeds, especially for strict vegetarians.
It was posted from another research:
Quote:
A survey of 326 algal species revealed that 171 species require exogenous vitamin B12 for growth, implying that more than half of the algal kingdom are cobalamin auxotrophs.
If nori needs B12 for growth, does that mean that all nori has significant amounts of B12? Can nori be reliable source?
Re: 54.5-58.6 microg/100 g in Nori (dry weight)
Quote:
medus
If nori needs B12 for growth, does that mean that all nori has significant amounts of B12? Can nori be reliable source?
This has been discussed for some years now - it is suggested that dried nori is somehow harmed (in terms of it's B12 levels) by the drying/aging process - as discussed earlier in this thread - but here's a study posted on PubMed suggesting that even dried Nori is useful. Personally, I don't have any experience with nori and therefore no opinions about the topic. :-)
Serum vitamin B12 levels in young vegans who eat brown rice.
Quote:
Serum vitamin B12 levels in young vegans who eat brown rice.
Suzuki H.
Department of Internal Medicine, Social Insurance Institute of Nagahori, Clinic, Osaka, Japan.
Abstract
A nutritional analysis was conducted on the dietary intake of a group of 6 vegan children aged 7 to 14 who had been living on a vegan diet including brown rice for from 4 to 10 years, and on that of an age-matched control group. In addition, their serum vitamin B12 levels and other data (red blood cell count, hematocrit, hemoglobin, etc.) were determined in the laboratory. In vegans' diets, 2-4 g of nori (dried laver), which contained B12, were consumed daily. Not a single case of symptoms due to B12 deficiency was found. There were no statistically significant differences between the two groups with respect to any of the examination data, including B12 levels (p < 0.05). Therefore, consumption of nori may keep vegans from suffering B12 deficiency.
PMID: 8926531 [PubMed - indexed for MEDLINE]
Re: 54.5-58.6 microg/100 g in Nori (dry weight) [PMID: 11430774]
This post will be a little long (again :) ), but somehow sums up where some of the confusion re. active B12 from vegan sources come from.
Quote:
Korn
The question about if we want B12 levels to continuously increase is of major importance whenever the existence of active, bioavailable B12 from plant sources is being discussed. The current "gold method" to test if B12 is active is using MMA tests. Here's one of the many things posted at veganhealth.org which IMO don't make any sense at all:
Quote:
Dried nori made MMA status worse, indicating that it can reduce B12 status and can possibly harm people who are B12-deficient. Raw nori kept MMA levels about the same, indicating that it didn't harm B12 status, but it did not help either.
I don't want to eat a source of any nutrient that keeps increasing the levels. Unless I'm deficient in a nutrient, in which case I need therapeutic amounts, all I want is something which keeps my good levels intact. Although health food sometimes can be used as medicine, I see food as food and medicine as medicine. If tomatoes are healthy and nutritious and keeps my levels of nutrient X intact, I can't complain about tomatoes because they aren't capable of removing headaches or because it keeps my levels of nutrient X intact instead of causing it to constantly increase. I just don't get the "kept MMA levels about the same, indicating that it didn't harm B12 status, but it did not help either", because the body utilizes a little B12 every day, and therefore the MMA levels should increase over time unless we consumed a valid source of *active* B12.
Another study mentioned in this thread , about vegan children who consumed nori daily concluded that "Not a single case of symptoms due to B12 deficiency was found. There were no statistically significant differences between the two groups with respect to any of the examination data, including B12 levels (p < 0.05). Therefore, consumption of nori may keep vegans from suffering B12 deficiency" is also commented on veganhealth.org. Instead of indicating that this could like great news re. the bioavailability/activity of B12 in nori, Jack Norris writes that it should be considered an 'unsolved mystery', and mentions that maybe they got some B12 from plants grown in manure etc.
Some of the B12 'case stories' at veganhealth.org are also highly questionable. One of them mentions a vegan in his eighties which was a excellent runner and had been in excellent health. He had been a vegan for 38 years and "attributed his ability to outperform younger people to his diet". Then, sometimes in his eighties he becomes sick, and they found that he had really low B12 levels, and that taking B12 helped. If someone haven't been taking B12 for 38 years on a vegan diet, and still have had excellent health in his eighties, this documents (as expected) that living on a vegan diet is really healthy. Lots of elders are B12 deficient, especially in their 80s and above. This case also suggests that even this particular person live don a vegan diet without supplements for a long time, it took 38 years for him to get any problems.
Here's the average lifespan (at birth) for humans - for some periods:
Upper Paleolithic: 33. At age 15: 39 (to age 54)
Classical Rome: 28. At age 15: 37 (to age 52)
Medieval Britain: 30. At age 21 (to age 59) as an average for British aristocrats.
Current world average (2010): 67.2
The above report about the man in his 80s is from USA. Average life expectancy at birth for North American males is what... 78 years?
It's known that B12 absorption abilities often decrease as we get older, which is particularly important for people on a diet low in B12. So - this man who has been vegan for 38 years without supplementing with B12 (not smart) seems to have gotten his symptoms after he got older than the average American males usually get.
Another case story at veganhealth.org was about a vegan who had been treated for phenobarbital for epileptic seizures for 8 years, and started to eat vegan since he was developing angina 4 years ago. His age was 56. He had been a (lacto-, I assume) vegetarian for 40 years, and was not supplementing with B12. He was found to have low hemoglobin levels. He got B12 supplements, and his B12 and hemoglobin levels were back in the normal range.
Use of Phenobarbital is often associated with decreased B12 levels - and increased homocysteine levels. Anyone - vegan or not - on phenobarbital for 8 years should have been given advice about supplementing with B12 since day one. Unfortunately a large portion of the vegan/B12 "information corpse" on internet ignores the importance of the many B12 "killers" out there, which distorts a lot of the info that's being handed out. The sad result of all this is that the information that's being delivered often is being distorted. The result is often that the general impression non-vegans easily may get about vegan nutrition is negative/flawed. I don't recommend anyone (omnivore, lacto-veg or vegan) to not take B12 supplements for 38 years without monitoring their B12 and MMA levels, but these cases come out plain wrong.
It's a little bit like when Vegan Society finally makes a video about vegan nutrition, and mentions calcium in one sentence - as something we can get from "supplements". We don't need supplements to get enough calcium on a vegan diet.
One of the tests above concluded that "although our results strongly suggest that the biologically active vitamin B12 compounds from the lyophilized purple laver are also active in man, the bioavailability of the algal vitamin B12 compounds in man remains to be determined in detail, because rat metabolism is not necessarily similar to human metabolism." This was 10 years ago, and AFAIK, no follow-up studies have been published yet. I think it's important to stress that tests on rats may not apply to other mammals, and at least this report suggests B12 in seaweeds isn't only available for non-mammal sea life. But why didn't they try this on humans in the first place?
One of the few tests that I know have been performed humans active B12 humans is a study Vegan Society was involved with, several years ago. Does any of you know if the results been published yet?
This part about veganhealth.org was a bit off topic, but is unfortunately relevant in terms of how the vegan/B12 topic and B12 levels in sea plants are being discussed.
Re: 54.5-58.6 microg/100 g in Nori (dry weight) [PMID: 11430774]
PMID: 9089476
http://www.ncbi.nlm.nih.gov/pubmed/9089476
Content and characteristics of vitamin B12 in some seaweeds
Quote:
Abstract
The vitamin B12 (B12) content in seven species of seaweed that are consumed frequently in Hokkaido, Japan, was microbiologically measured using Escherichia coli 215. Asakusanori (Porphyra tenera), maruba-amanori (Porphyra suborbiculata) and akaba-gin-nansou (rhodo-glossum pulcherum) showed higher B12 content than the other species, although the content varied greatly among samples in the same species. A bioautography on a thin-layer plate holding a mixture of silica gel and cellulose, differentiation of B12 and its analogues using a binding specificity of intrinsic factor and haptocorrin, and comparison of the B12 concentration determined by the radioisotope dilution assay method using the intrinsic factor as the B12-binding protein with that by the bioassay method, predominantly showed B12 in maruba-amanori and B12 analogues in wakame (Undaria pinnatifida) and akaba-gin-nansou. The B12 uptake of akaba-gin-nansou from artificial seawater was similar to that of asakusanori that contained only B12.
Here's another interesting report. It suggests that maruba-amanori contains "B12", while wakame contain "B12 analogues". But - please don't forget this well known report, posted here in 2007, suggesting that B12 (cobalamin) "in raw nori can be changed into harmful Cbl analogues by the drying process".
In general it's also worth noting that...
1) most reports before 2000 were quite vague in terms of whether B12 found in algae etc was active or not.
2) Although there are now are methods which claim that they can measure whether B12 found in food products is active or not, there's still no reason to not perform real tests on whether the B12 which is claimed to be active actually has an effect on MMA and homocysteine levels (even if both these references are questionable according to some sources, they may be the best we have right now).
3) If tests show that B12 found in plant or algae products have a positive effect on MMA in non-human mammals, it should be easy to perform similar tests on humans. Until that is done, there's IMO no reason to use eg B12 from algae instead of other supplements - and not only that: there may be no reason to use B12 from algae even if its' proven to contain active, 'true' B12 which corrects MMA and homocysteine levels in humans either. The main thing re. testing MMA/hcy effect of B12 found in plants/algae is probably mainly of 'philosophical' reasons. By that I mean that if one can prove that B12 from eg dulse, nori, chlorella etc contain bioactive B12 which is so stable that it in raw or dried form can be used by humans to improve their B12 status, one could end the already weak/false pseudo-argument against vegan diets who are based on the categorical assumption that useful B12 can only be found in animals.
