Everything Vegetarians Need to Know About Vitamin B12

By Katie Trant | Last Updated: August 6, 2015

Vegetarians & Vitamin B12

Vegetarians & Vitamin B12
Everybody asks vegetarians how we get our iron, or how we get enough protein, and those are certainly important. But we can’t forget about another totally important player for any vegetarian – B12. So this month we’re getting down and detailed about B12.

What is Vitamin B12?

Vitamin B12 is one of eight B-vitamins. It’s a water-soluble vitamin, which exists in several forms and it contains the mineral cobalt.

What does Vitamin B12 do?

Important stuff! Vitamin B12 plays a vital role in the normal functioning of the brain and nervous system, as well as cell metabolism, fatty acid metabolism, amino acid metabolism, and the synthesis and regulation of DNA.

Where is Vitamin B12 found?

Get this – no plants, fungi, or animals are capable of producing this vitamin. All B12 is produced by certain strains of bacteria that have the enzymes required for its synthesis. For example, algae are believed to acquire B12 through a symbiotic relationship with heterotrophic bacteria in which the bacteria supply B12 in exchange for fixed carbon from the algae.

B12 can be produced industrially through bacterial fermentation synthesis – this is where most of the B12 in supplements or fortified foods comes from.

What foods contain Vitamin B12?

Vitamin B12 is found in most animal foods, including meat, fish, poultry, eggs, and milk products; the amount and quality of the B12 depends on the diet of the animal.

Other than some fermented foods, there are very few non-animal food sources of biologically active B12. Many vegan foods are fortified with vitamin B12, including non-dairy milks, breads, cereals, meat substitutes, and some types of nutritional yeast. It is important to note that not all nutritional yeast contains B12. It must be fortified, so if you’re relying on nutritional yeast for your B12, check the label carefully.

Pseudo what now?

To make matters concerning B12 and plant-based foods a bit more complicated, there is a group of biologically inactive B12-like analogues referred to as pseudovitamin-B12. These are found alongside B12 in humans and in many food sources. In most cynobacteria, including Spirulina, pseudovitamin-B12 is predominant. Pseudo B12 can make it difficult to test for B12 deficiency, as it can imitate true biologically active B12 in blood tests.

How much Vitamin B12 do we need?

Recommendations vary from country to country. The US recommended daily average (RDA) for adults is 2.4 µg (micrograms) of vitamin B12/day. This bumps up to 2.6 µg during pregnancy, and 2.8 during lactation and breastfeeding. Since B12 is a water-soluble vitamin, toxicity doesn’t seem to be a problem; what the body doesn’t need is simply excreted in our urine.

What happens if you don’t get enough Vitamin B12?

Very low B12 intakes can cause anemia (this is not the same as iron deficiency anemia) and can potentially cause severe damage, especially to the brain and nervous system. Heart disease and pregnancy complications are also of concern with B12 deficiency.

Typical B12 deficiency symptoms include low energy, tingling, numbness, reduced sensitivity to pain, blurred vision and a sore tongue.

Our livers are able to store several years worth of vitamin B12, so deficiency symptoms may not appear for 5 years or more. This is important for long-term vegetarians and vegans, who should be tested for B12 deficiency, especially if following a diet that doesn’t include eggs or dairy. Vegans eating a macrobiotic or raw diet that avoids fortified foods are at an especially high risk.

Adults over 50 may not meet the RDA without supplementation, regardless of diet. And individuals with digestive system disorders such as Crohn’s disease, celiac disease or IBS may not be able to absorb enough B12 from food to maintain healthy body stores and require supplementation as well.

Should you take Vitamin B12 supplements?

The only way to know for sure if you’re lacking B12 is to see your doctor about getting a blood test. Blood homocystine levels may provide a more accurate measurement for those following a vegan diet, as opposed to blood B12 or blood counts.

If you’re following a strict vegan diet, pay attention. The only reliable vegan sources of B12 are fortified foods such as non-dairy milks, breads, cereals, and fake “meat” products. But not all of these products are fortified and not all are fortified equally, so you should get to know your labels.

If you’re following a vegan diet you should either eat B12 fortified foods that add up to at least 2.4 µg/day OR take a daily B12 supplement. If you’re going the supplementation route, it’s important to know that the body’s ability to absorb B12 from supplements is limited – aim for a supplement with around 10 µg or more.

The bottom line?

B12 is important stuff! If you’re in an at-risk group for deficiency, get yourself tested. If you’re vegan, read labels and understand which foods you’re eating are fortified and how that adds up, and/or consider a daily B12 supplement. If you’re vegetarian and are pregnant or are considering becoming pregnant, talk to your doctor about whether or not you need a B12 supplement.

About Katie Trant

Katie is a university-trained nutritionist and professional writer based in Stockholm, Sweden. She is a vegetarian of more than two decades, and is passionate about real food. Her blog The Muffin Myth is all about approachable nutrition.

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Comments

A few years ago I found out I was severely B12 deficient. I felt horrible, barely able to do my job and care for my children, and I wanted to sleep all the time. My tongue was always sore and swollen enough that I would often bite it. I always assumed I would be fine for B12 because I still ate eggs and dairy, but I guess it wasn’t enough.

The B12 content of eggs and dairy totally depends on the diet of the animals they came from. So even those of us who do eat eggs and dairy should get our B12 levels tested now and then. Glad you’re ok now!

Just so everyone understands how important B12 is I am only mostly okay. I still have balance and neurological issues from the low B12. Those issues are unfortunately permanent. Luckily for me they are fairly mild, but if you turn off the lights I will always look like I’m drunk.

Thanks, Kate for posting this important article. I have been vegan for 24 years and get my B-12 levels tested every year. I supplement by chewing B-Fresh gum, which contains 300 percent RDA of B-12 and is an excellent source of water-soluble calcium. It’s sweetened with xylitol and comes in a variety of flavors (my fave is cinnamon). No, I don’t work for the company! 🙂

Thank you for an article that spells the B12 issues out so well. As we turn ever more toward a vegan diet at our household (still one hold-out flexitarian and one vegan-leaning vegetarian), I am more concerned with this vitamin than ever I expected to be.

This is going to sound like a dumb question, I’m sure, but I’ll ask anyway. If animals don’t make the B12, how does it get in their meat and such? I’m guessing they host the bacteria that manufactures it.

If so, that raises another question for me: If other animals host the bacteria, is it possible humans do as well? Presumably, Science has already tested and found no traces, but I’m curious whether my assumptions are correct.

Hi Kathryn, good question. Animals contain B12 in their flesh, milk, and eggs by a few different mechanisms. One is that they have bacterial “contamination” of their food and are ingesting the B12 producing microorganisms. Ruminants like cows and sheep can also absorb B12 made by their gut bacteria (hosting it themselves, as you said. Some animals eat poop, which, as gross as it sounds, can be a rich source of B12 (note that I didn’t list it as a potential source for people though!), and lastly, animals eat other animal flesh, milk, or eggs, which contain B12. There is some evidence that some B12 synthesis does occur in the human small intestine, and that an amount of B12 also gets “recycled” in our intestines from intestinal bile. But this isn’t a reliable source of B12 for us, so we’ve got to get it in our diets or supplement.

Thanks for that information, Katie, and for your quick response. I’d like to delve a little deeper, if possible. If you have the information handy, could you please point me to links to studies that explain this (preferably in lay terms)? Even the abstracts would help.

Your explanation of the contaminated food and poop sources of the bacteria make me wonder whether, in our ultra-clean world, we have eliminated this natural source of B12 in our diets. I wonder if people who live in more hygienically challenging environments might have more B12 in their systems.

Hi Kathryn, if you’ve got access to a database of journal articles, such as PubMed, I’d start there. It’s a big job to sift through all the abstracts – good luck! Your point on the hygiene hypothesis is an interesting one. We’ve certainly done a lot of damage to ourselves by living in an ultra-sterilized environment. It would be interesting to look at those who are moving back to a more natural environment and a diet rich in fermented foods (teeming with friendly bacteria!). I’m not sure what the B12 status is like in those populations, but an educated guess is that it would be better.

Thanks for the PubMed suggestion, Katie. I’ll see what I can find there. If ever you do run across your sources, it’d would be wonderful if you could provide links to them. Thanks again for writing this article. It answers several questions I’ve had about B12.

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