vitamin b12

What to Do About Vitamin B12 If You’re A Vegetarian or Vegan

Are vegans and vegetarians at risk of vitamin B12 deficiency?

Don from the comments asks:

I’ve been vegan for over 10 years and the single nutrient that’s not found in vegetarian diets is vitamin B12. Vitamin B12 is created by a biological interaction between microbes and fertile soil, so traditionally people could be vegetarian without being susceptible to anemia. In addition, people used to drink unpasteurized milk which was a good source of B12, but not so for pasteurized milk…….. I’d appreciate your opinions on the subject. Thanks.

The issue of vitamin B12 and the vegan/vegetarian diet is an old canary, and unlike other perceptions of plant based diets, this one has some teeth.

Plant foods are not good sources of vitamin B12, and you sure as hell need it.

So let’s go over what this means if you’re thinking of making the plant-based diet switch. There are some legitimate B12 risks that I’ll address, but it’s important to compare this drawback with the many benefits of being a herbivore.

vitamin b12 food sources

A Brief Overview of Vitamin B12

Vitamin B12 is an essential micro-nutrient that’s not made by plants or animals. It’s made by bacteria. Animal cells can store the B12 made by bacteria and plants can’t, so animal foods tend to be a good source and plants are not.

A lot of the bacteria in human bodies make vitamin B12, but most of them live in your colon and B12 is digested in your ileum, which is north of your colon. So you literally poop most of it out.

Poop is actually a rich source of vitamin B12, and one of the reasons we haven’t traditionally been B12 deficient is because for most of our history we have lived in close proximity to our animals, and ate vegetables that were grown in soil fertilized by maneur. We’re far separated from those conditions now, which is why vitamin B12 deficiency can creep up from time to time.

What Does Vitamin B12 Do?

Vitamin B12 performs the following functions in your body:

  • supports nervous system development and function
  • supports red blood cell production
  • helps metabolize all food sources (carbohydrate, protein, fat)

If you don’t get enough vitamin B12 you might:

  • feel weak/nautious
  • lose memory
  • experience fevers
  • have weird stuff start happening to your tongue
  • lose sense of taste/feeling
  • experience depression

None of the above stuff sounds like very much fun to me, so it’s best to make sure you get enough vitamin B12 in your diet!

vitamin b12 and riboflavin


Your body uses vitamin B12 very efficiently. You need about 0.003 g/day, and you can actually get by on about 1/10th that much if you have to.  Your body can actually store vitamin B12 for up to 20 years, and a 3 year supply of vitamin B12 in your liver is common.

For this reason acute B12 deficiency is uncommon even if you’re a vegetarian/vegan.

However, if vitamin B12 is an issue it’s usually not because you’re not receiving it in your diet.

Most Vitamin B12 problems are due to stomach/intestine problems rather than diet deficiency.

Sometimes your stomach will stop making a compound called intrinsic factor that’s essential to digest B12, and sometimes autoimmune disorders and complications from surgeries prevent the ileum from digesting it. These problems trump the prevalence of diet induced B12 deficiency.

However, that still begs the question……

Are Vegans and Vegetarians At Risk For Vitamin B12 Deficiency?


Properly planned vegan/vegetarian diets should be fine, but the truth of the matter is a lot of plant eaters get vitamin B12 in sub-optimal amounts.

A good illustration of this point is a study published in the American Journal of Clinical Nutrition that summarized existing research on vitamin B12 and the vegetarian diet. A good summary can be found on this graph here. Vegans and vegetarians regularly have lower plasma levels of B12 than omnivores. Other studies have suggested that as much as 60% of vegetarians have some form of B12 deficiency, and these numbers are especially true for people who don’t take supplements or eat a raw food diet.

So the danger is real, however the issue needs to be put in perspective.

heart disease high blood pressure stroke

B12 Deficiency vs. Diabetes, Heart Disease, and Cancer

Perhaps I’m being a tad bit groupish, but I think people exaggerate the dangers of  B12 deficiency. It is a serious problem, but an important fact is often overlooked:

Vegetarians and vegans with B12 deficiency often have a variety of other nutrient deficiences as well. 

Or in other words, the people with B12 deficiency are that way primarily because they’re not very good at taking care of themselves, not because they’re vegans.

If you still don’t get my drift, consider the following points:

  • The chances of irreversible B12 deficiency in vegetarians is about 1 in 5,000 over the course of your life
  • The chances of dying from a heart attack or stroke are about 1 in 2
  • The chances of contracting breast cancer for women is about 1 in 7 over the course of her lifetime
  • The chances of contracting prostate cancer for men is about 1 in 6 over the course of our lifetimes

Similar discrepancies exist for conditions like osteoperosis, diabetes, hypertension, etc.

The truth is, I think it’s very instinctive to guard your eating habits because it reflects in who you are as a person. So people who aren’t “on your side” are quick to cling to any evidence that justifies their bad habits.

That doesn’t negate the problem, but it does explain the cacophony from the opposition.

Are There Vegetarian Food Sources for Vitamin B12?

There are, but none of them are very good.

Like I said before, plants don’t store vitamin B12 and it’s only made from bacteria. So potential food sources include:

  • fermented vegetables (sauerkraut, tempeh, korean laver)
  • nori (a seaweed)
  • spirulina, other freshwater algaes

But do yourself a favor and don’t rely on any of these exclusively.

It helps that a lot of vegan/vegetarian foods are fortified with B12, and that’s often enough to keep you above water.

However, it’s a good idea to take a supplement.

vitamin b12 supplement

B12 Supplements

B12 supplements are cheap, and actually contain way more B12 than you actually need. 5mcg a day is more than enough, but typical dosages usually range from 100 to 5000 mcg per pill.

Regarding this issue, I’d make two points:

  • Supplementation is usually enough to shield you from dangers of B12 deficiency
  • Eating a diet rich in probiotics helps

Advice for Taking B12 Supplements

When taking a B12 supplement, I’d be careful of the following points:

  • make sure methylcobalamin is the active ingredient. It’s the form of B12 that’s most readily digested. (Methyl cobalimin is very common)
  • it’s better to chew or dissolve B12 pills than swallowing them outright
  • other vitamins reduce the bioavailibility of B12, so buy a B12 vitamin separately. 
If you follow the above points, you should be fine.
Some Good Sources On This Issue (Layperson):
Wolfgang, Hermann, et. al. “Vitamin B-12 Status, Particularly Holotranscobalimin II and Methylmalonic Acid Concentrations, and Hyperhomocysteinemia in Vegetarians.” American Journal of Clinical Nutrition. July 2003, pgs. 131-136
Miller, Donald, et. al. “Vitamin B-12 Status in a Macrobiotic Community” American Journal of Clinical Nutrition. 1991. Pgs. 525-529.
Herrmann, Wolfgang, et. al. “Vegetarian Lifestyle and Monitoring of Vitamin B-12 Status” Clinica Chimica Acta.  December 2002.  Pgs. 47-59.
Haddad, Ella, et. al. “Dietary Intake and Biochemical Hematologic, and Immune Status of Vegans Compared with Nonvegetarians.” American Journal of Clinical  Nutrition.  September 1999. pgs. 5865-5935.
Donaldson, Michael. “Metabolic Vitamin B12 Status on a Mostly Raw Vegan Diet with Follow-Up Using Tablets, Nutritional Yeast, or Probiotic Supplements” Nutrition and Metabolism.  August 2000.  pgs. 229-234.

12 thoughts on “What to Do About Vitamin B12 If You’re A Vegetarian or Vegan”

  1. Thank you so much, Jonathan, for your thorough research and your clear and succinct writing.

    So many vegans and vegetarians do not realize that there are some vitamins and nutrients which are difficult to get in a plant based diet. They might not even know which vitamins they are missing or what those vitamins do. But even those who are aware do not know how to compensate for them. Thank you for addressing all of these issues and bringing a potential deficiency to the spotlight which might otherwise go unnoticed.

    Another excellent article! Thank you for clearing up the issues of B12 in the vegetarian and vegan diet.


  2. So, even though you say in another article “synthetic vitamins are bad for you”, you would still recommend one for B12? I’m guessing there isn’t a whole-food based supplement for B12?


    1. Sarah,

      Astute observation and yes……B12 is the exception. That’s because there is no whole plant food that gives you vitamin B12 in a highly bio-available form, which means deficiency is a small but legitimate risk, and therefore a regular B12 pill is a good idea.


      1. Thanks for the tip…looks like you use B12 by itself, is that absorbed better than a B-complex vitamin or do you just take it by itself to avoid unnecessary synthetic vitamins?


      2. Sarah,

        I’m not a huge fan of synthetic vitamins. I take a B12 supplement all by itself. It’s also absorbed better this way. Multi-nutritional vitamins typically interfere with the absorbance of vitamin B12.


  3. […] in small quantities.I’ve written extensively about vitamin B12 before, and it’s the only nutrient not supplied in sufficient quantity by vegan and plant based diets.Truth be told any B12 supplement will probably do the trick, and you don’t have to worry […]


  4. Not sure if anyone struggles with malabsorption in the gut and therefore cannot get enough B12 even with supplementation and is getting the injections for B12 currently but for those struggling with that kind of B12 deficiency, I recently heard about a new oral prescription alternative to the injections called Eligen B12. I recently read that it works even if you don’t have intrinsic factor (so even if you don’t have normal gut absorption). Apparently it came out a month or two ago. Has anyone heard of it or tried it??


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