by Jack Norris, RD
Vitamin B12 is arguably the most important nutrient in vegan nutrition.
B12 is found in meat, dairy, and eggs. In contrast, there are no reliable plant sources of B12. Luckily, B12 is made by bacteria and doesn’t need to be obtained from animal products allowing vegans to obtain B12 through supplements and fortified foods.
But what if someone doesn’t bother?
A 1955 study from the U.K., one of the earliest studies of vegans, found a high prevalence of B12 deficiency with some vegans suffering from nerve damage and dementia. There have been many documented cases of individual vegans becoming deficient. I’ve known many vegans who’ve neglected B12 and subsequently experienced fatigue and temporary neuropathy that resolved upon obtaining a reliable source. Research on non-supplementing vegans has shown them to have elevated levels of homocysteine which might increase the risk for cardiovascular disease and cognitive decline.
For these reasons, the overwhelming consensus in the mainstream nutrition community and among vegan health professionals is that supplementation is necessary for the optimal health of vegans.
Despite overwhelming evidence for the importance of vegans obtaining a consistent, reliable source of B12, some vegan advocates still believe that “plant foods provide all the nutrients necessary for optimal health,” and don’t address B12 when promoting the vegan diet. Others emphasize that humans need only small amounts of B12 and that it can be stored in the body for years, implying that there’s nothing with which to concern ourselves. While it’s true that at the time many people become vegan, they have enough B12 stored to prevent overt B12 deficiency for many years, markers of deficiency begin to increase shortly after intake stops.
If you look into the details of vitamin B12, you’ll quickly find out that they’re expansive and complicated. But one thing is simple: Vegans should ensure a reliable source of B12 according to the recommendations on our Daily Needs page.
Overt B12 Deficiency
Fatigue is a typical symptom of vitamin B12 deficiency. Vitamin B12 is normally needed for red blood cells to divide and become active. Without enough B12, fatigue can result due to a lack of oxygen-carrying capacity of the red blood cells. This condition is known as macrocytic or megaloblastic anemia.
B12 also protects the nervous system and without it, permanent damage can result, such as blindness, deafness, and dementia. B12-related nerve damage often manifests as tingling in the hands or feet and, if not treated, can progress to more serious symptoms.
To complicate matters, folate also helps red blood cells to divide. Many vegans obtain high amounts of folate from their diet and, due to a quirk in physiology, some vegans might get so much folate that even with a B12-deficiency their blood cells will continue to divide. This can mask a B12-deficiency, preventing the fatigue that can be an early warning sign.
Subclinical B12 Deficiency
Homocysteine is a byproduct of protein metabolism that the body clears with the help of B12. Many studies have found that vegans who don’t supplement with B12 have a high prevalence of elevated homocysteine without overt symptoms of deficiency.
There’s evidence that subclinical B12 deficiency and/or elevated homocysteine levels increase the risk of cognitive decline, cardiovascular disease (especially stroke), early mortality, and possibly low bone mineral density.
In contrast to vegans who don’t supplement with B12, vegans who supplement tend to have homocysteine levels well within the healthy range. More info can be found in Homocysteine and Mild B12 Deficiency in Vegans.
What Vegans Need to Know
The most critical information to know is how much B12 to take. We list our B12 recommendations the Daily Needs page, along with the most important notes about supplementing.
You also might be interested in our thoughts about the naturalness of a vegan diet in our article, Can a Natural Diet Require Supplements?
For opinions of health professionals not affiliated with VeganHealth, see this open letter from health professionals and vegan organizations, What Every Vegan Should Know about Vitamin B12.
Vitamin B12: Are You Getting It?
This article provides a thorough review of the scientific literature on vitamin B12 and the vegan diet.
Facts about Supplemental B12
Rationale for VeganHealth’s B12 Recommendations
- Brief History of B12 Recommendations for Vegans
- Government Recommendations
- Institute of Medicine’s Recommendations
- European Food Safety Authority’s Recommendations
- Cyanocobalamin Absorption
- Vegan Health B12 Recommendations
- Appendix A. Minimizing Methylmalonic Acid Levels
- Appendix B. Clinical Trials: Impact of B12 Supplementation on Metabolites
- Serum B12
- Methylmalonic Acid
- Notes on Clinical Trials of B12 Supplementation
- Appendix C. Factorial Approach
- Appendix D. Pregnancy and Breastfeeding
- Appendix E. IOM Recommendations for People Over Age 50
- Appendix F. ASMBS B12 Recommendations for People after Bariatric Surgery
Coenzyme Supplements: Methylcobalamin and Adenosylcobalamin
Are Multivitamins an Adequate Source of B12 for Vegans?
- Clinical Trials in Nonvegetarians
- Extrapolating Wolters et al.’s Findings to Vegans
- Observational Studies
- B12 Malabsorption
- Degradation of B12 under Experimental Conditions
- Yamada et al.’s 2008 Study of B12 in Fortified Beverages and Multivitamins
- Kondo et al. and Herbert et al.’s Research on Multivitamins circa 1980
- Potential Improvements in the Accuracy of Nutrition Labeling
- B12 Transport Proteins and Multivitamins
- Observational Study of B12 in Fortified Non-Dairy Milks
- Anecdotal Reports
- Dangers of Recommending “Take a Multivitamin”
- Appendix A: Personal Experiment
Elevated Vitamin B12 Levels and Mortality
- PREVEND Raises Concern
- Negative Outcomes in Vitamin B12 Supplementation Trials
- Vitamin B12 and Cyanide
- Cyanocobalamin and Kidney Disease
Should I Get My B12 Status Tested?
Measuring B12: Why the Confusion?
- B12 Amounts Versus B12 Activity
- Microbiological Assay
- R-protein Assay
- Intrinsic Factor Assay
- Intrinsic Factor Assay Shown to Be Unreliable in Humans
- Ochromonas Malhamensis Fares Better Than an Intrinsic Factor Assay
- Paper Chromatography
- Methods for Measuring B12 Activity of a Food
- Bacterial Contamination
Vitamin B12 in Plant Foods
- Plant Foods with Practically No Detectable B12 Analogue
- Fermented Foods
- Mankai (Duckweed)
- Seaweeds (Macroalgae)
- Soil and Organic Produce as a B12 Source for Vegans
Intestinal Bacteria as a Vitamin B12 Source
Overt B12 Deficiency: Nerve Damage and Anemia
Subclinical B12 Deficiency and Homocysteine in Vegans
- Background on Homocysteine
- Homocysteine in Vegetarians and Vegans
- B12 Status and Prospective Studies of Cognitive Decline
- B12 Metabolites and Brain Volume
- Randomized Controlled Trials of B-Vitamins, Cognitive Decline, and Brain Atrophy
- Research on Vegetarians and Vegans
- Summary of B12 and Cognition
- Mortality and Cardiovascular Disease
- Bone Mineral Density
35 thoughts on “Vitamin B12”
I’ve been taking B12 for years as soon as I started a vegan diet. I took test two times and the results were good. At that time I was not consuming any seaweed which could interfere with the results. Now I started experimenting with low daily doses of B12, however with methylcobalamin, since cyano form does not dissolve in water at all. I take 25 mcg of MeCbl solution two times a day with food, with hours of interval. I believe that should be enough to saturate intrinsic factor fully and reach the DR of B12. Should I get checked on B12 levels after some time to see if this method works good enough, or there should be no problem?
Hi Sandro – We can’t give advice on each person’s personal B12 regimen, but check out this article: https://veganhealth.org/should-i-get-my-b12-status-tested. And here are our recommendations: https://veganhealth.org/daily-needs/#Vitamin-B12.
Dear Jack and colleagues! Could you please comment on this study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6642017/
Seems you didnt review it in Elevated B12 section. It supports the idea that high B12 levels _cause_ elevated lung cancer risk.
Here are my comments: Elevated B12 and Lung Cancer
The information in here is not true, and not well researched. There are plenty of vitamin b12 sources that are vegan. Sure, some seaweed has little to no b12, but not all. 2.5 grams of dried Pyropia yezoensis has over 35% of the RDI of b12. Fermented foods, however are by far the best source of vitamin b12 for vegans. One 10oz glass of kombucha contains over 340% of the RDI for b12. There’s absolutely no need for b12 supplements, and I’m inclined to believe the only reason you are saying this is because you have some sort of monetary incentive to.
Please see this article: https://veganhealth.org/vitamin-b12-plant-foods/. We’re unaware of any published research showing that kombucha contains B12.
very interesting post, thanks for collecting all this info! I recently began researching about B12 sources. I found two studies which show that Chlorella vulgaris is a source of active cobalamin. Specifically, supplements of C. vulgaris apparently contains both cyanocobalamin and metylcobalamin, as determined per HPLC analyses . Also, C. vulgaris supplements had activity reducing the risk of anemia, proteinuria and edema in pregnant women . Since B12 can only be produced by prokaryotes, C. vulgaris must obtain B12 from the media which is produced by bacteria or archaea. Thus, I think that it is worth considering C. vulgaris supplements as sources of active cobalamin. What do you think?
 N. Jaliliana, G. D. Najafpour and M. Khajoueib, 2019. Enhanced Vitamin B12 Production using Chlorella vulgaris
 Shiro Nakano, Hideo Takekoshi and Masuo Nakano, 2010. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women
We have written about chlorella and B12 here: https://veganhealth.org/vitamin-b12-plant-foods/#chlorella. Until chlorella is shown to consistently reduce MMA levels in humans (we are unaware of studies showing this), we cannot recommend it as a source of vitamin B12.
I recently found a B-Complex product that appears to be sourced from quinoa sprouts. The product includes B-12, but I’m concerned that this may be an inactive analogue unless they are just using the quinoa as a medium for bacteria-derived B-12. The product is produced by Swanson, and when I look at the Supplement Facts on the back, each vitamin lists next to it in parentheses “PANMOL(r) B-COMPLEX from quinoa sprouts.”
There’s very little information on the PANMOL site, and the research section does not list any actual research. I’m guessing they sell directly to supplement manufacturers, but this is unclear as well. They’re an Austrian company, but it looks like they partner with a company in the USA called Stauber. The Swanson product I bought is vegan, but it looks like the Stauber product may not be, but that’s neither here nor there since I’m just looking for info about the PANMOL itself. The Stauber site claims that all of the B vitamins are in their active forms.
I’m having a hell of a time trying to find actual research on this. Do you think this is a B-12 analogue or actual biologically-active B-12. I’m concerned that I may have purchased an ineffective product. My Google searches have found nothing on B-12 from quinoa sprouts either. Thanks for your help!
If “cyanocobalamin” isn’t listed in the ingredients, then I wouldn’t rely on it as a sole source of vitamin B12.
Thanks! I managed to track down the FDA GRAS Notification for PANMOL. It just says “cobalamine” in the document but not which kind, so I will be looking for a different supplement.
Hi Meredith- were you able to find out if PANMOL contains cyanocobalamin OR methylcobalamin? Are you still using the product you mentioned?
So now we have a VIABLE Plant Based Source of B-12 that is literally part of the plant’s biomass. Water Lentils AKA Duckweed.
We looked into duckweed and determined it is much too soon to conclude that it is a reliable source of vitamin B12 for humans.
What’s with the new study about high B12 intake and hip fractures (in older women)? I am in particular taken aback by the extreme discrepancy between what the study labels high intake (20 mcg of B12) and the daily dosage of supplement I take (500 mcg).– an older man
Given that the findings from this study on B12 and hip fractures are statistically weak, that they’re based on an observational study (which only shows correlations), and go against research showing a beneficial effect of higher B12 levels on bones, we don’t think this evidence is enough to justify changing our recommendations. While we generally recommend 500 µg/day for people over 65 (because of the research explained here), if you get your B12 levels tested regularly and they’re within the normal range, it would appear safe to follow the recommendations for people under 65.
Duckweed – Have you heard that there is evidence that it contains active B12?
Research sounds promising
We looked into duckweed and determined it is much too soon to conclude that it is a reliable source of vitamin B12 for humans.
We added information about duckweed here: https://veganhealth.org/vitamin-b12-plant-foods/#duckweed
As well as a blog post: https://veganhealth.org/is-duckweed-a-source-of-vitamin-b12/
I am vegan because I care for nonhuman animals who are mistreated by humans. Their lives are worth the same, if not more that humans, therefore I won’t take anything that comes from them. It is just not ethical. I already have lots of benefits from being vegan: lots of energy; strong immune system, I do not get cold or flu even if I am exposed to it or I’ll get immunity by having a sub clinical illness which gives me immunity against that specific strain; if I get a cut or another injury, I heal fast. Another benefit I get is my risks for cancer and cardiovascular disease are reduced.
Since animals make vitamin B12 in their system, is there an specific microbial source that can strengthen my own bacteria producing B12?
Hi Norma, the place in our intestines where bacteria make vitamin B12 is lower down than where we absorb it. Which means that we do not absorb vitamin B12 made by the bacteria in our intestines. The only reliable vegan sources of vitamin B12 are fortified foods and supplements.
A vegan mom since pregnancy is low on breastmilk and feeding her 5 mos old a vegan formula . This homemade formula is Almond milk , spirulina, nutritional brewers yeast, sacha,powders, coconut oil are main ingredients . Can an baby aborsorb vita b 12 from such a mix?
Please see the Pregnancy, Infants, and Children section of our website for more information and resources for vegan infants. Specifically, this section says:
“Vegan parents should not try to make their own infant formulas as this often leads to poor child development. Although more research is desirable, it appears that soy infant formulas are safe. See below for information regarding soy formulas.”
In addition to real concerns about vitamin B12 from the formula you describe, calories, protein, calcium, iron, zinc and many other nutrients could be too low or too high. Please, for the sake of this infant’s health and well-being, strongly encourage this mom to change her plans. Some suggestions:
• consult a certified lactation specialist to address breastfeeding issues
• use a commercial soy formula in place of the homemade formula
• consult with a registered dietitian to discuss feeding vegan infants and children.
Is there any reason to avoid the cyano form when breastfeeding infants, in case maybe it could burden their young liver, or any other reason?
Cyanocobalamin is used in infant formulas so it is likely that this form can be used by infants.
Hi. I am obese and trying to eat healthier. Went on a 10 day whole plant based diet through a work-wide health challenge and while I don’t envision adopting this diet for life, I would like to try and use the recipes I like and try to avoid dairy and oil while limiting meat consumption to poultry now and then. I started taking B12 with the challenge (I’m on day 15). I had no idea what to buy. My bottle says 3000 mcg and directions say to take one daily. Please let me know if this is too much. Also, I am diabetic, on medications, and have blood work taken evey 6-8 months. My doctor has never said anything about my vitamin B12. He did put me on vtiamin D3, 2000 units, daily. I would appreciate your advice. Would you please email your response as I found this website while scrolling and not sure I’ll get back! Thank you very much.
According to the National Institutes of Health, (https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/#h8) vitamin B12 can interfere with some medications including a drug used to treat diabetes. It’s important to tell your health care provider about any supplements that you take.
Hi I’m having much acne since I’m taking cyanocobalamin pills. I have stopped taking them as a temporary measure. I am vegan and I don’t know what I should do in the long term. Any advice? I’m quite worried. Thank you in advance!
B12 fortified foods or a multivitamin or supplement with much lower amounts of B12. See the “Option 1” column in the B12 table here: https://veganhealth.org/daily-needs/
What’s your opinion regarding taking B12 individually or as part of a “B complex” ie. with several B-vitamins? Does the latter increase absorption?
I’m not aware of any evidence that taking B12 as part of a vitamin B complex increases its absorption.
I mean this article is missing (got from web arhive) https://web.archive.org/web/20170505225006/http://veganhealth.org/b12/inc
I took that page down when I migrated everything to the new site because it was so outdated and due to the fact that spurious correlations between disease and high B12 levels are too burdensome to track just to say we did it. If any research comes out that seriously implicates high B12 intakes as a cause of disease, we’ll cover it on our updates blog which you can sign up for at the bottom of each page on the website.
Seems that the old site article “Elevated Serum B12 and Increased Risk of Disease” dissapears. Can’t find it… Did you remove it? Why?
Lots of information and still looking for a clear answer.. Do we need! B12 supplements as vegan, vegetarian or meat eater?
Vegan or near-vegan: yes, see Daily Needs
Someone who eats animal products multiple times a day (in other words NOT a vegan or near vegan): no