This article is from the Vegetarianism FAQ, by firstname.lastname@example.org (Michael Traub) with numerous contributions by others.
The data on B12 is still coming in, so it is impossible to say
"Its no problem....", however, the latest information suggests
that acquiring enough B12 is not as problematic as it was once
thought. If you are concerned about inadequate B12, there are
many foods which are fortified with B12, in addition to vitamin
pills. Here is the most recent information:
From the book:
Simply Vegan: Quick Vegetarian Meals, by Debra Wasserman and
Nutrition Section by Reed Mangels, Ph.D., R.D.
Published (1990/1991) by the Vegetarian Resource Group,
P.O. Box 1463, Baltimore, MD 21203, (410) 366-VEGE.
Summary: The requirement for vitamin B12 is very low.
Non-animal sources include Nutri-Grain cereal (1.4 ounces
supplies the adult RDA) and Red Star T-6635+ nutritional
yeast (1-2 teaspoons supplies the adult RDA). It is
especially important for pregnant and lactating women,
infants, and children to have reliable sources of vitamin
B12 in their diets.
Vitamin B12 is needed for cell division and blood formation.
Plant foods do not contain vitamin B12 except when they are
contaminated by microorganisms. Thus, vegans need to look to
other sources to get vitamin B12 in their diet. Although the
minimum requirement for vitamin B12 is quite small, 1/1000 of a
milligram (1 microgram) a day for adults, a vitamin B12
deficiency is a very serious problem leading ultimately to
irreversible nerve damage. Prudent vegans will include sources
of vitamin B12 in their diets. However, vitamin B12 deficiency
is actually quite rare even among long-term vegans.
Bacteria in the human intestinal tract do make vitamin B12.
However, the majority of these bacteria are found in the
large intestine. Vitamin B12 does not appear to be absorbed
from the large intestine.
Normally, vitamin B12 is secreted into the small intestine
along with bile and other secretions and is reabsorbed, but
this does not add to the body's vitamin B12 stores. Since
small amounts of vitamin B12 are not reabsorbed, it is
possible that eventually vitamin B12 stores will be used up.
However, we may be quite efficient at re-using vitamin B12
so that deficiency is rare.
Some bacteria in the small intestine apparently produce
vitamin B12 which can be absorbed. This is one possible
explanation for why so few cases of vitamin B12 deficiency
are reported. Perhaps our bacteria are making vitamin B12
At this time, research is continuing on vitamin B12
requirements. Some researchers have even hypothesized that
vegans are more efficient than the general public in
absorbing vitamin B12. Certainly for other nutrients, such
as iron, absorption is highest on low dietary intakes.
However, these are only speculations. We need to look for
reliable dietary sources for vitamin B12 until we can
determine whether or not other sources can supply adequate
Although some vegans may get vitamin B12 from inadequate
hand washing, this is not a reliable vitamin B12 source.
Vegans who previously ate animal-based foods may have
vitamin B12 stores that will not be depleted for 20 to 30
years or more. However, long-term vegans, infants,
children, and pregnant and lactating women (due to increased
needs) should be especially careful to get enough vitamin
Few reliable vegan food sources for vitamin B12 are known.
Tempeh, miso, and seaweed often are labeled as having large
amounts of vitamin B12. However, these products are not
reliable sources of the vitamin because the amount of
vitamin B12 present depends on the type of processing the
food undergoes. Also, Victor Herbert, a leading authority
on vitamin B12 states that the amount on the label cannot be
trusted because the current method for measuring vitamin B12
in foods measures both active and inactive forms of vitamin
B12. The inactive form (also called analogues) actually
interferes with normal vitamin B12 absorption and
metabolism. These foods may contain more inactive than
active vitamin B12.
The RDA (which includes a safety factor) for adults for
vitamin B12 is 2 micrograms daily. Two micrograms of
vitamin B12 are provided by 1 teaspoon of Red Star T-6635+
yeast powder or 1-1/2 teaspoons of mini-flake yeast or 2
rounded teaspoons of large-flake yeast. Of course, since
vitamin B12 is stored, you could use larger amounts of
nutritional yeast less often. A number of the recipes in
this book contain nutritional yeast.
Another alternative source of vitamin B12 is fortified
cereal. Nutri-Grain cereal does contain vitamin B12 at this
time and 1.4 ounces of Nutri-Grain, or a little less than 1
cup, will provide 2 micrograms of vitamin B12. We recommend
checking the label of your favorite cereal since
manufacturers have been known to stop including vitamin B12.
New labeling laws do not require labels to include the
actual amount of vitamin B12 in a food. However, added
vitamin B12 will be listed under ingredients and you can
write to the company inquiring about the amount of vitamin
B12 in a serving.
Other sources of vitamin B12 are fortified soy milk (check
the label as this is rarely available in the US), vitamin
B12 fortified meat analogues (food made from wheat gluten or
soybeans to resemble meat, poultry or fish) [Midland Harvest
products contain B12.], and vitamin B12 supplements. There
are vitamin supplements which do not contain animal