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Thread: Watanabe: "Vitamin B12 Sources and Bioavailability"

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    Ex-admin Korn's Avatar
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    Default Watanabe: "Vitamin B12 Sources and Bioavailability"

    There are some important factors that needs to bear in mind when reading about B12 in plants: Is the B12 found in plants active in humans? If B12 would be found in a number of plant sources and drinking water, how much B12 would we need to consume (say, per 100g food/water)? How much B12 would humans need per day if they wouldn't have been exposed to unnatural and natural B12 "enemies"?

    Here's an excerpt of what Fumio Watanabe writes about B12 from non-animal sources in "Vitamin B12 Sources and Bioavailability":

    Vegetables. Many studies have been performed to measure vitamin B12
    content in various vegetables. For decades, edible bamboo shoots have been believed to contain considerable amounts of vitamin B12. However, it turned out that they do not contain appreciable amounts of vitamin B12; however, certain compounds showing vitamin
    B12–like activity (known as the alkali-resistant factor) were found in them (44). Similar results were found in cabbage, spinach, celery, garland chrysanthermum, lily bulb, and taro
    (44). Only trace amounts of vitamin B12 (<0.1 lg/100 g of wet weight edible portion), which was estimated by subtracting the alkali-resistant factor from total vitamin B12, were found in broccoli, asparagus, Japanese butterbur, mung bean sprouts, tassa jute, and water shield (44). These vegetables may have the ability to take up vitamin B12 found in certain organic fertilizer.
    I will not eat anything that walks, swims, flies, runs, skips, hops or crawls.

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    Ex-admin Korn's Avatar
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    Default Re: Watanabe: "Vitamin B12 Sources and Bioavailability"

    Vegetables.Many studies have been performed to measure vitamin B12 content in various vegetables. For decades, edible bamboo shoots have been believed to contain considerable amounts of vitamin B12. However, it turned out that they do not contain appreciable amounts of vitamin B12; however, certain compounds showing vitamin B12–like activity (known as the alkali-resistant factor) were found in them (44). Similar results were found in cabbage, spinach, celery, garland chrysanthermum, lily bulb, and taro (44). Only trace amounts of vitamin B12 (< 0.1 μg/100 g of wet weight edible portion), which was estimated by subtracting the alkali-resistant factor from total vitamin B12, were found in broccoli, asparagus, Japanese butterbur, mung bean sprouts, tassa jute, and water shield (44). These vegetables may have the ability to take up vitamin B12 found in certain organic fertilizer.Mozafar (45) demonstrated that the addition of an organic fertilizer, cow manure, significantly increases the vitamin B12 content in barley kernels and spinach leaves. Mozafar and Oeftli (46) investigated uptake of vitamin B12 by soybean roots under water culture conditions. Sato et al. (47) reported that a high level of vitamin B12 is incorporated into a vegetable, kaiware daikon (radish sprout), by soaking its seeds in vitamin B12 solutions before germination. The amount of vitamin B12 incorporated into kaiware daikon increases up to about 170 μg/100 g of wet sprout with 3-hr soaking of seeds in 200 μg/ml vitamin B12 solution. These vitamin B12–enriched vegetables may be of special benefit to vegans or elderly persons with food-bound vitamin B12 malabsorption.
    Tea Leaves and Tea Drinks.Considerable amounts of vitamin B12 are found in various types of tea leaves: green (0.1–0.5 μg vitamin B12 per 100 g dry weight), blue (about 0.5 μg), red (about 0.7 μg), and black (0.3–1.2 μg) tea leaves (48).When a corrinoid compound was isolated from Japanese fermented black tea (Batabatacha), the compound was identified as vitamin B12 (49). When vitamin B12–deficient rats were fed this tea drink (50 ml/day, equivalent to a daily dose of 1 ng vitamin B12) for 6 weeks, urinary methylmalonic acid excretion (an index of vitamin B12 deficiency) of the tea drink–supplemented rats decreased significantly compared with that of the deficient rats (49). These results indicate that the vitamin B12 found in the fermented black tea is bioavailable in rats. However, only 1–2 liters of consumption of fermented tea drink (typical regular consumption in Japan), which is equivalent to 20–40 ng vitamin B12, is not sufficient to meet the RDA of 2.4 μg/day for adult humans.
    Edible Algae.Various types of edible algae are used for human consumption the world over. Dried green (Enteromorpha sp.) and purple (Porphyra sp.) lavers (nori) are the most widely consumed among the edible algae and contain substantial amounts of vitamin B12(32 to 78 μg/100 g dry weight; Ref. 39). In Japanese cooking, several sheets of nori (9 × 3 cm; about 0.3 g each) are often served for breakfast. A large amount of nori (< 6 g) can be consumed from certain sushi, vinegared rice rolled in nori. However, edible algae other than these two species contain none or only traces of vitamin B12 (39). Dagnelie et al. (53) reported the effect of edible algae on the hematologic status of vitamin B12–deficient children, suggesting that algal vitamin B12 appears to be nonbioavailable. As bioavailability of the algal vitamin B12 is not clear in humans, my colleagues and I characterized corrinoid compounds to determine whether the dried purple and green lavers and eukaryotic microalgae (Chlorella sp. and Pleurochrysis carterae) used for human food supplements contain vitamin B12 or inactive corrinoids. My colleagues and I found that these edible algae contain a large amount of vitamin B12 without the presence of inactive corrinoids (5457).To measure the bioavailability of vitamin B12 in the lyophilized purple laver (Porphyra yezoensis), the effects of feeding the laver on various parameters of vitamin B12were investigated in vitamin B12–deficient rats (58). Within 20 days after vitamin B12–deficient rats were fed a diet supplemented with dried purple laver (10 μg vitamin B12/kg diet), urinary methylmalonic acid excretion became undetectable and hepatic vitamin B12 (especially coenzyme vitamin B12) levels significantly increased. These results indicate that vitamin B12 from the purple lavers is bioavailable in rats.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.
    Edible Cyanobacteria.Some species of the cyanobacteria, including Spirulina, Aphanizomenon, and Nostoc,are produced at annual rates of 500–3000 tons for food and pharmaceutical industries worldwide (61). Tablets containing Spirulina sp. are sold as a health food fad, since it is known to contain a large amount of vitamin B12 (62). We found that commercially available spirulina tablets contained 127–244 μg vitamin B12 per 100 g weight (63). When two corrinoid compounds were characterized from the spirulina tablets, the major (83%) and minor (17%) compounds were identified as pseudovitamin B12(adeninly cobamide) and vitamin B12, respectively (Fig. 2). Several groups of investigators indicated that pseudovitamin B12 is hardly absorbed in mammalian intestine with a low affinity to IF (64, 65). Furthermore, researchers showed that spirulina vitamin B12 may not be bioavailable in mammals (63, 66). Herbert (67) reported that an extract of spirulina contains two vitamin B12 compounds that can block the metabolism of vitamin B12. And van den Berg et al. (68) demonstrated that a spirulina-supplemented diet does not induce severe vitamin B12 deficiency in rats, implying that the feeding of spirulina may not interfere with the vitamin B12metabolism. Further studies are needed to clarify bioavailability of spirulina vitamin B12 in humans.
    Vitamin B12–Fortified Cereals.Ready-to-eat cereals fortified with vitamin B12 are known to constitute a great proportion of dietary vitamin B12 intake in the United States (7). Several groups of investigators suggested that eating a breakfast cereal fortified with folic acid, vitamin B12, and vitamin B6 increases blood concentrations of these vitamins and decreases plasma total homocysteine concentrations in elderly populations (73). Fortified breakfast cereals have become a particularly valuable source of vitamin B12 for vegetarians and elderly people.
    I will not eat anything that walks, swims, flies, runs, skips, hops or crawls.

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