Summary
The requirement for vitamin B12 is very low. Non-animal sources include Red
Star Vegetarian Support Formula or T-6635+ nutritional yeast (a little less
than 1 Tablespoon supplies the adult RDA), and vitamin B12 fortified soymilk.
It is especially important for pregnant and lactating women, infants, and children
to have reliable sources of vitamin B12 in their diets.
The Need for Vitamin B12
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, 1/1,000,000
of a gram (1 microgram) a day for adults [1], 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.
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.
Bacteria in the human intestinal tract do make vitamin B12. The majority of
these bacteria are found in the large intestine. Vitamin B12 does not appear
to be absorbed from the large intestine [1].
Possible Vitamin B12 Sources
Some bacteria in the small intestine do produce vitamin B12 [2]. The amount
of vitamin B12 which is produced does not appear adequate to prevent vitamin
B12 deficiency [3].
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
[1] 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 B12.
Reliable Vegan Sources of Vitamin B12
A number of reliable vegan food sources for vitamin B12 are known. One brand
of nutritional yeast, Red Star T-6635+, has been tested and shown to contain
active vitamin B12. This brand of yeast is often labeled as Vegetar-ian Support
Formula with or without T-6635+ in parentheses following this new name. It is
a reliable source of vitamin B12. Nutritional yeast, Saccharomyces cerevisiae,
is a food yeast, grown on a molasses solution, which comes as yellow flakes
or powder. It has a cheesy taste. Nutritional yeast is different from brewer's
yeast or torula yeast. It can often be used by those sensitive to other yeasts.
The RDA (which includes a safety factor) for adults for vitamin B12 is 2.4 micrograms
daily [4]. 2.4 micrograms of vitamin B12 are provided by a little less than
1 Tablespoon of Vegetarian Support Formula (Red Star T-6635+) nutritional yeast.
A number of the recipes in this book contain nutritional yeast.
Another source of vitamin B12 is fortified cereal. We recommend checking the
label of your favorite cereal since manufacturers have been known to stop including
vitamin B12.
Other sources of vitamin B12 are vitamin B12-fortified soy milk, vitamin B12-fortified
meat analogues (food made from wheat gluten or soybeans to resemble meat, poultry
or fish), and vitamin B12 supplements. There are vitamin supplements which do
not contain animal products.
Vegans who choose to use a vitamin B12 supplement, either as a single supplement
or in a multi-vitamin should use supplements at least several times a week.
Even though a supplement may contain many times the recom-mended level of vitamin
B12, when vitamin B12 intake is high, not as much appears to be absorbed. This
means in order to meet your needs, you should take the vitamin several times
a week.
Tempeh, miso, and sea vegetables often are reported to have large amounts of
vitamin B12. These products, however, are not reliable sources of the vita-min
because the amount of vitamin B12 present depends on the type of processing
the food undergoes [1, 5]. The standard 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 vita-min B12 absorption
and metabolism [1, 6]. Fermented foods and sea vege-tables may contain more
inactive than active vitamin B12.
Some vitamin B12 appears to be found in organically grown plants, but in extremely
small amounts. According to one study [7,8], more than 23 cups of organically
grown spinach would have to be eaten every day in order to meet the adult RDA
for vitamin B12. Produce cannot be depended on as a reliable vitamin B12 source
because the level of vitamin B12 in plants varies widely depending on the type
of plant and the soil in which it is grown. Also, vitamin B12 analogues may
be found in soil and absorbed by plants. If these ana-logues are present, they
could either interfere with the plants uptake of vitamin B12 or with the usefulness
of the plant's vitamin B12 for humans.
References
1. Herbert V. Vitamin B12: Plant sources, requirements, and assay. Am J Clin
Nutr 1988; 48: 852-858.
2. Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human small intestinal
bacteria. Nature 1980; 283: 781-782.
3. Callender ST, Spray GH. Latent pernicious anemia. Br J Haematol 1962; 8:
230-240.
4. Institute of Medicine, Food and Nutrition Board: Dietary Reference Intakes
for Thiamin, Riboflavin, Niacin, Vitamin B-6, Folate, Vitamin B-12, Pantothenic
Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
5. Specker BL, Miller D, Norman EJ, et al. Increased urinary methylmalonic acid
excretion in breast-fed infants of vegetarian mothers and identification of
an acceptable dietary source of vitamin B12. Am J Clin Nutr 1987; 47: 89-92.
6. Kondo H, Binder MJ, Kohhouse JF, et al. Presence and formation of cobal-amin
analogues in multivitamin-mineral pills. J Clin Invest 1982; 70: 889-898.
7. Mozafar A. Is there vitamin B12 in plants or not? A plant nutritionist's
view. Vegetarian Nutrition: An International Journal 1997; 1/2: 50-52.
8. Mozafar A. Enrichment of some B-vitamin in plants with application of organic
fertilizers. Plant and Soil 1994; 167: 305-11.