Vitamin B-12 is naturally found in meat (especially liver and shellfish), milk and eggs. Animals, in turn, must obtain it directly or indirectly from bacteria, and these bacteria may inhabit a section of the gut which is posterior to the section where B-12 is absorbed. Thus, herbivorous animals must either obtain B-12 from bacteria in their rumens, or (if fermenting plant material in the hindgut) by reingestion of cecotrope fæces. Eggs are often mentioned as a good B-12 source, but they also contain a factor that blocks absorption.[1] Certain insects such as termites contain B-12 produced by their gut bacteria, in a manner analogous to ruminant animals.[2] An NIH Fact Sheet lists a variety of food sources of vitamin B-12.
According to the U.K. Vegan Society, the present consensus is that any B-12 present in plant foods is likely to be unavailable to humans and so these foods should not be relied upon as safe sources, as the B-12 analogues can compete with B-12 and inhibit metabolism. Also, vegan humans who eat only plant based foods must ordinarily take special care to supplement their diets accordingly. the only reliable vegan sources of B-12 are foods fortified with B-12 (including some soy products and some breakfast cereals), and B-12 supplements.[3]
While lacto-ovo vegetarians usually get enough B-12 through consuming dairy products, vitamin B-12 may be found to be lacking in those practicing vegan diets who do not use multivitamin supplements or eat B-12 fortified foods. Examples of fortified foods often consumed include fortified breakfast cereals, fortified soy-based products, and fortified energy bars. Claimed sources of B-12 that have been shown through direct studies[4] of vegans to be inadequate or unreliable include, laver (a seaweed), barley grass, and human gut bacteria. People on a vegan raw food diet are also susceptible to B-12 deficiency if no supplementation is used[5].
References[]
- ↑ Doscherholmen, A; et al. (1975) Proc Soc Exp Biol Med, Sep;149(4):987-90
- ↑ Template:Cite journal
- ↑ Walsh, Stephen, RD. Vegan Society B-12 factsheet. Vegan Society. Retrieved on 2008-01-17.
- ↑ Norris, Jack, RD. B-12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods. VeganHealth.org. Retrieved on 2008-01-17.
- ↑ Template:Cite journal
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Some of this page is derived from Wikipedia. The original article was at Vitamin B12. The list of authors can be seen in the page history. As with The Case for a Vegan World, the text of Wikipedia is available under the GNU Free Document License. |