The short answer? Yes. But does that make a diet without animal products somehow flawed? Not when you understand where the b12 comes from.
Where does vitamin b12 come from, anyway?
B12 is bacteria born and in our sanitized food environment it’s all cleaned off the veggies. On a non-animal food diet you don’t get it. Animal products are contaminated enough that it’s there.
In contrast to most vitamins which are synthesized by plants, vitamin b12 is unique as it is synthesized naturally by bacteria growing in soil, water and the intestinal tract of animals. That’s why the vast majority of plants don’t contain vitamin B12, and any trace B12 in plants are due to microbial contamination from soil or manure.
The best dietary sources of vitamin B12 are foods of animal origin, such as meats. Vitamin B12 originating in protein sources, like meats, are derived from the animals ingestion of cobalamin-containing animal tissues, in addition to vitamin B12 synthesized by bacteria within the animals own digestive tract.
So this doesn’t mean a plant-based diet is inherently deficient. It just means we’ve gotten so clean with food processing these days when it comes to veggies (barring the occasional ecoli contamination) that we can only get this particular bacteria from animal products which is…well, contaminated!
Although vitamin B12 is found in animal foods it is not synthesized by plants or animals. Only bacteria make biologically active vitamin B12—animal tissues store “bacteria-synthesized B12,” which can then be passed along the food chain by animals eating another animal’s tissues. Ruminants (like cows, goats, sheep, giraffes, llamas, buffalo, and deer) are unique in that bacteria in their rumens (stomachs) synthesize vitamin B12, which is then passed down and absorbed by their small intestines. Lions and tigers get their B12 from eating these grazers.
The human gut also contains B12-synthesizing bacteria, living from the mouth to the anus.8 The presence of these bacteria is an important reason that disease from vitamin B12 deficiency occurs very rarely in people, even those who have been strict vegetarians (vegans) all of their lives. The colon contains the greatest number of bacteria (4 trillion/cc of feces), and here most of our intestinal B12 is produced.
However, because B12 is absorbed in the ileum, which lies upstream of the colon, this plentiful source of B12 is not immediately available for absorption—unless people eat feces (don’t gasp). Feces of cows, chickens, sheep and people contain large amounts of active B12. Until recently most people lived in close contact with their farm animals, and all people consumed B12 left as residues by bacteria living on their un-sanitized vegetable foods.
~ Dr. John McDougall
If you found yourself hitting rewind to catch Dr. McDougall’s mentioned form of b12 supplement, I’ve got your back. Dr. McDougall recommends the hydroxy or methyl forms of vitamin b12 supplement.
As little as 0.3 to 0.65 micrograms per day of vitamin B12 has cured people of megaloblastic anemia;9 however, to add an extra margin of safety I have recommended a higher dosage of 5 micrograms per day. You may be surprised to discover that you cannot purchase these tiny dosages. Supplements sold contain 500 to 5000 micrograms per pill. These exaggerated concentrations will correct by passive absorption B12 deficiency caused by disease of the intestine.16-17 Everyone else is being overdosed by a factor of 1000. If you are an otherwise healthy vegan and are using typical dosages of B12 (500 micrograms or more per pill), a weekly dose of this vitamin will be more than sufficient. ~ Dr. John McDougall
And if you’re ready for a boatload more of details, documentation, and references on the “where to get your b12” question, here is more from Dr. McDougall: Vitamin B12 Deficiency: The Meat-Eater’s Last Stand.
“Reliable Non-animal Sources of Vitamin B12
by Reed Mangels, Phd., R.D., Vegetarian Resource Group
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 Vegetarian 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. those sensitive to other yeasts can often use it.
The RDA for adults for vitamin B12 is 2.4 micrograms daily (1). About 2 rounded teaspoons of large flake Vegetarian Support Formula (Red Star T-6635+) nutritional yeast provides the recommended amount of vitamin B12 for adults (2). A number of the recipes in this book contain nutritional yeast.
Another source of vitamin B12 is fortified cereal. For example, Nature’s Path Optimum Power cereal does contain vitamin B12 at this time and about a half cup of this cereal will provide 2.4 micrograms of vitamin B12 (3). 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 that do not contain animal products.
Vegans who choose to use a vitamin B12 supplement, either as a single supplement or in a multivitamin should use supplements regularly. Even though a supplement may contain many times the recommended 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 a daily vitamin B12 supplement of 5-10 micrograms or a weekly vitamin B12 supplement of 2000 micrograms (4).
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