B 12



Where does vitamin B-12 come from?

Certain bacteria found in the mouth and intestines of animals (including humans) convert cobalt salts into vitamin B-12 (which is why B-12 is called cobalamin). When the bacteria consume the cobalt, B-12 enzymes are produced that help the body make red blood cells, produce myelin (the fatty substance that forms a protective barrier around nerves), produce acetylcholine (a neurotransmitter that helps with memory and learning), and help produce DNA and RNA. Until very recently, the conventional wisdom was that animal products were the sole sources of vitamin B-12. In fact, many studies of B-12 in vegan diets started with the premise that the vegan diet contains no sources of B-12 (becauseof the common knowledge that it is made by bacteria in the bodies of animals). However, the science regarding how much B12 is actually provided by various dietary sources, and even how much B-12 a person actually needs, has substantially evolved.

For instance, a recent study by Fumio Watanabe published in the highly respected, peer-reviewed journal Experimental Biology and Medicine found that widely held beliefs about dietary sources of B-12 may be profoundly inaccurate. Watanabe summarized over a decade of research conducted by himself and his colleagues, and numerous other researchers, regarding the content and bioavailability of B-12 in various foods. Watanabe found that many foods that had been thought to contain substantial amounts of B-12 in fact did not, and many foods that had been thought to contain little or no B-12 in fact contained substantial amounts.


Surprising sources of B-12:

  • Tempe:
    Watanabe found that: “A soybean-fermented food, tempe, contains a large amount of vitamin B-12 (0.7 to 8 μg/100 g).” That amount is as much or greater than the amount of B-12 contained in a serving of meat, eggs, or milk. This finding should not be that surprising, given that the fermentation process relies heavily on bacteria, and at least some of the bacteria involved is likely to produce B-12.
  • Seaweed:
    Watanabe’s study also revealed that: “Various types of edible algae are used for human consumption the world over. Dried green (Enteromorpha sp.) and purple (Porphyra sp.) lavers (nori) are the most widely consumed among the edible algae and contain substantial amounts of vitamin B12 (32 to 78 μg/100 g dry weight).” This amount equals or exceeds even the highest amount provided by some of the highest animal sources of B-12. Of particular interest is the fact that Watanabe cited two studies that showed that vegans who consumed nori and/or chlorella (the green substance in all green vegetables) had serum vitamin B-12 concentrations “twice as high as those not consuming these algae.”
  • Spirulina:
    Watanabe also reviewed studies of Spirulina and other species of cyanobacteria. He found that while Spirulina contains substantial amounts of B-12, ranging from “127–244 μg vitamin B12 per 100 g weight”, the B-12 present in these sources is largely a form of the vitamin known as “pseudovitamin B-12,” which may not be readily absorbed by the body. Watanabe also noted that the science regarding absorbability of the vitamin is still evolving. He pointing out that different studies had arrived at different conclusions regarding whether this form of the vitamin was bioavailable or not, and concluded that: “Further studies are needed to clarify bioavailability of spirulina vitamin B12 in humans.”
  • Tea:
    Perhaps one of the most surprising of these sources was tea leaves. Watanabe found that considerable amounts of vitamin B-12 are found in various types of tea leaves: green (0.1–0.5 μg vitamin B12 per 100 g dry weight), blue (about 0.5 μg), red (about 0.7 μg), and black (0.3–1.2 μg) tea leaves.”

What does this all mean?

The point is that there is still a lot that scientists don’t know about sources of B-12 in the diet and that there are many varying opinions, among the top scientists, regarding the B-12 content and absorbability of vegan foods. Which leads me to a question of my own: Why are so many lay people so adamant that they have the B-12 thing all figured out?

Vicious debates arise in which people on every side of the issue demand that their point of view is correct, when the truth is that at this time scientists only know a few things about vitamin B-12 and what little they do know they is uncertain.

So, what are the symptoms of vitamin B-12 deficiency?

Given the role of B-12 in forming red blood cells, building nerve tissue, and producing neurotransmitters, you can understand the problems that an absence of it would cause: anemia, neurological problems, peripheral neuropathy, spinal cord problems, early onset dementia and memory problems.

But numerous other symptoms that are also commonly attributed to B-12 deficiency: weakness, light-headedness, rapid heartbeat, pale skin, easy bruising, weight loss, indigestion, constipation, sore tongue, eye twitching, tickling sensation in the hips, migraines, fatigue, insomnia, and irregular menstruation.

This is a long list of common ailments that could potentially have many explanations (my favorite is the tickling in the hips). So it is almost impossible to determine definitively from a handful of symptoms whether you are suffering from a B12 deficiency, or from something else.

Should you get tested for B-12 deficiency?

You can try, but your test may not tell you a thing. A blood test is the most common method of testing for B12 deficiency. However, recent research from the University of St. Louis has indicated that a blood test alone may be insufficient to determine whether someone is vitamin B-12 deficient. In fact, in one study it was found that more than three quarters of patients with otherwise normal B-12 blood levels exhibited increased levels of methylmalonic acid (MMA). The concentration of MMA increases when vitamin B-12 is in shortage. That finding casts some doubt as to the reliability and accuracy of B-12 blood tests. The researchers therefore suggest that doctors who believe their patients are lacking in vitamin B-12, should also test for proper levels of MMA. This, of course, does not make the diagnosis conclusive either though.

Other experts are recommending that if vitamin B-12 deficiency is suspected as the cause of damage to the nervous system, an analysis of cerebrospinal fluid is necessary. Of course, this is a very invasive procedure that is best avoided if you can help it, and again, is not conclusive.

So, how much B-12 do we need?

We know that B12 is made by naturally occurring bacteria in animals from the digestion of cobalt salts. We know the body needs it for several important bodily functions We also know that the body doesn’t need very much of it and that the body can store it and reuse it for years (some experts say 3 years, some say 7 years and others say for an entire lifetime).

One thing that most scientists agree on right now is that we need less than, though many choose to word it in a more cautionary “not more than”, 1 mcg daily of B-12. That amount would be enough to completely reverse B-12 deficiency in a person who had no B-12 stores of their own to rely on. The actual daily optimum amount is a mere .01-.25 mcg/d. (Herbert) Interestingly, this number has been lowered recently as scientists learn more about vitamin B-12.

According to the amounts of B-12 found in vegan foods in the Watanabe study, I can have a couple cups of tea, or grab some vegetable sushi wrapped in nori once a month, and I’m taking in more than the proper amount of B-12 by the most recent standards!

According to Dr. Vivian V. Vitrano, B-12 deficiency is a complete myth that vegans, raw fooders and fruititarians have no need to worry about. She argues, very convincingly, that B-12 is readily available in our own mammalian bodies as well as fruits and vegetables.

This is not the most popular stance on the subject today, and even many vegan authorities have rebutted her argument on various website forums and maintain that vegans need to take B-12 supplements. As someone who has been vegan for over a decade, and who does not supplement with any vitamin pills, with no signs of any vitamin deficiencies, I tend to lean toward Dr. Vitrano’s viewpoint. But I invite you to research for yourself and make up your own mind.

Should I consider eating some animal products to make extra sure that I don’t get a B-12 deficiency?

On the USDA website I found an interesting study that was published as an article called “Are You Vitamin B 12 deficient?” in the August 2000 issue of Agricultural Research magazine. Three-thousand men and women were tested for B-12 deficiencies in the Framingham (Massachusetts) Offspring Study. Researchers found that 39 percent had plasma B-12 levels in the “low normal” range—below 258 picomoles per liter (pmol/L). While this is well above the currently accepted deficiency level of 148 pmol/L, some people exhibit neurological symptoms at the upper level of the deficiency range, explained study leader Katherine L. Tucker.
Interestingly, the researchers found no association between plasma B-12 levels and meat, poultry, and fish intake, even though these foods supposedly supply the bulk of B-12 in the average diet. This perplexing situation of meat eaters with low levels of B-12 has caused many researchers to conclude that digestive disorders and problems with absorption, rather than deficiencies in the diet, must be the culprit. “It’s not because people aren’t eating enough meat,” researcher Katherine Tucker has said, “The vitamin isn’t getting absorbed.”

Some researchers blame overuse of antibiotics and antibacterial cleaners. They just cannot understand why people who eat animal products that contain so much vitamin B-12 are B-12 deficient. I cannot help but think of the large numbers of people consuming dairy with high calcium levels who have osteoporosis. There is clearly more to this B-12 thing than researchers know at this point in time.

Everybody’s talking about what happens if you don’t get enough B-12, but shouldn’t we also avoid getting too much?

According to scientific researcher Victor Herbert in his article, Vitamin B-12: plant sources, requirements, and assay, published in the American Journal of Clinical Nutrition, “…as we discover more and more about excesses of any nutrient, we discover harms we did not know existed. It will probably turn out eventually that too much vitamin B-12, like too much of anything, is harmful.”
I remember a few years ago when scientists were lauding the cancer-preventing benefits of Beta Carotene and doing studies where they gave people large doses of Beta Carotene pills. They had to stop the studies because the research subjects taking beta carotene supplements were dying of cancer at alarming rates. It turned out that when a person eats vegetables that contain Beta Carotene, they get the right amount-- in combination with other phytochemicals that scientists are just now learning about that also prevent cancer. But when we take pills with large doses of one isolated nutrient, it can be harmful.

Food for thought.


There are no definitive answers in science right now about the best sources for making sure that the body is getting and utilizing enough vitamin B-12, or what the best sources are to obtain it for our bodies, or even how much a body needs. But one thing’s for sure, we who have been vegan for a few years have seen this sort of debate about the supposed deficiencies of the vegan diet regarding many nutrients, most notably protein and calcium. And until the majority of people in the world become vegan, these sorts of debates will continue. In the meantime , it’s comforting to know that if you’re vegan and not taking B-12 pills (or shots), the most recent science says that if you are eating a variety of plant foods, including things like seaweed, you will be fine. If you prefer to supplement with pills, we recommend DEVA supplements.

Controversies like this are a big driving force behind why vegans tend to be some of the most well-educated people on the planet when it comes to nutrition. What’s more, we tend to educate others. It’s all a part of our social evolution.



  • Watanabe, Fumio. Vitamin B12 Sources and Bioavailability. Experimental Biology and Medicine, 2007; 232(10): 1266-1274.
  • Omenn, GS. Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial, Natl Cancer Inst. 1996 Nov 6;88(21):1550-9.
  • Herbert, V. Vitamin B-12: plant sources, requirements, and assay. Am J Clin Nutr Sep. 1988; 48(3):852-858.