Vitamin b-12 discussion

[Guest guest]

I am presently a graduate student in nutrition and one of my texts _ Present

Knowledge in Nutrition 8th edition (2001) ed. by Bowman and say that

" Only microorganisms retain the ability to synthesize cobalamins and

microbial synthesis pathways have been recently elucidated in a series of

elegant studies. Because plants do not use cobalamins, the source of

cobalamins in all higher animals is the product of microbial synthesis ...

All animals require vitamin B12 and obtain it ultimately from the products of

microbial synthesis. Ruminant animals carry bacteria that synthesize

cobalamins in their rumen. Other vegetarian animals appear to obtain vitamin

B12 from eating feces or feces-contaminated vegetable food. Omnivorous

animals including humans obtain vitamin B12 from the products of animal

origin, including meats, dairy products and eggs. It is possible that human

also obtain vitamin B12 from sewage-contaminated foods. In the last 30 years,

synthetic vitamin B12 has been added to many cereals and other foods in the

Western world, so fortification is a major source of the vitamin.

In Krause's Food, Nutrition and Diet Therapy, 10th edition (2000) they state

that " Food of plant origin contain the vitamin only through contamination or

bacterial synthesis. Many people believe that fermented foods contain

sufficient vitamin B12 to meet their needs; however, this theory is not

supported by analysis. ... In contrast, some cooked sea vegetables contained

vitamin B12 in the same range as beef liver (through sewage contamination??)

Individuals consuming strictly vegetarian diets, particularly after 5 to 6

years, typically show lower circulating levels of vitamin B12 unless they

supplement with the vitamin ... and elsewhere in the book... " Vegans of long

standing may develop megaloblastic anemia because of vitamin B12 deficiency,

inasmuch as the vitamin occurs only in foods of animal origin. Curiously,

this is less of a problem in areas where sanitation is poor because

contaminating bacteria can serve as a source of the vitamin. The hazard of

vegan diets is that the presence of high levels of folate may mask the

neurologic damage of B12 deficiency. " They recommend that vegan take

supplements.

That such a necessary vitamin is rarely found on plants and then seemingly

only because of contamination, it stands to reason that Mother Nature must

have expected us to get this most precious vitamin from more plentiful and

more reliable foods -- namely animal foods. Even if cooked sea vegatables

might have some vitamin B12 - there is no guarantee -- and just how prevalent

would contaminated sea vegetables have been during our evolution? There's

always feces I suppose. But would feces be considered animal food by a strict

vegan.

Namaste, Liz