From wheeler@super.org Wed Feb 24 18:00:44 1993
Date: Thu, 1 Oct 92 10:52:03 EDT
From: wheeler@super.org (Ferrell S. Wheeler)
To: tms@cs.umd.edu
Subject: PCRM B12



VITAMIN B12: FACTS FOR VEGETARIANS

* Vegetarians and B12
     Vegetarian foods are easily the most healthful. Vegetarians live longer,
have less heart disease, less cancer, less risk of stroke, and less of other
serious illnesses compared to meat-eaters. Vegetarian meals provide adequate
levels of all nutrients--with the possible exception of vitamin B12. B12 is
critical in the formation of red blood cells and the function of the nervous
system. B12 deficiency is rare. The body has several years' worth stored at
any given time. 

* Traditional Sources of B12
     B12 is not made by animals or plants; it is made solely by microorganisms,
such as bacteria and algae. Some of the B12-developing organisms may remain
on vegetables consumed by people, producing a small amount of the vitamin.
Traditional Asian miso and tempeh, made from soybeans, also contain enormous
amounts of B12 because of the microorganisms used during manufacture. But
improved hygiene and modern processing methods have all but eliminated these
traditional sources of B12 from the industrialized nations' diet. Meat-
eaters' source of B12 is bacteria living in the digestive tracts of the
animals they eat. The vitamin works its way into the animals' muscles,
organs, and milk.

* Getting the Vitamin
     For those who abstain from eating animal products, special care in getting
enough B12 is recommended. Fortunately, this is very easy. B12 is in all
common multivitamin tablets, and many foods are enriched with B12. These
include many breakfast cereals, fortified nutritional yeast, and fortified
soy milk. Some supplements, such as spirulina, are purported to contain B12,
but actually contain none at all. On vitamins or food labels, look for B12
by its chemical name: cyanocobalamin. The Recommended Daily Allowance is two
micrograms per day, but experts believe only one microgram per day is
sufficient.1 There is no known risk in consuming too much B12, but high doses
are not necessary or recommended.
     By far, the most common cause of B12 problems is not the lack of the
vitamin in the diet, but a problem in absorbing it, caused by a lack of a
chemical in the body called the intrinsic factor. Doctors can easily test
whether a person has a normal ability to absorb B12. For those who do not,
no amount of the vitamin in foods will help, and periodic injections of B12
are necessary.

Reference:
1. Herbert V. Vitamin B12: plant sources, requirements and assay. Am J Clin
Nutr 1988;48:852-58.

Physicians Committee for Responsible Medicine
P.O. Box 6322
Washington, DC 20015
(202) 686-2210
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