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.
Mild B12 Deficiency
Homocysteine is a byproduct of protein metabolism that the body clears with the help of vitamin B12. Elevated homocysteine levels are linked with increased risks of dementia, heart disease, and stroke.
From 1999 to 2003, many studies found that vegans who weren’t supplementing with vitamin B12 had unusually high levels of homocysteine. In contrast, one study found that vegans who supplement with vitamin B12 (an average of 5.6 mcg/day) had homocysteine levels well within the healthy range.
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.
Vitamin B12 Supplements
- Facts about Supplemental B12
- B12 in Supplements is Produced by Bacteria
- Avoid Exposing B12 to Light
- Brewer’s and Nutritional Yeasts Must be Fortified
- Chew B12-Only Supplements
- B12-Fortified Toothpaste is Reliable
- Avoid Cooking all Your B12
- Vitamin B12: Rationale for VeganHealth’s 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 of B12 Supplementation
- Appendix C. Factorial Approach
- Appendix D. Pregnancy and Breastfeeding
- Appendix E. IOM Recommendations for People Over Age 50
- Coenzyme Supplements: Methylcobalamin and Adenosylcobalamin
- 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”
- PREVEND Raises Concern
- Negative Outcomes in Vitamin B12 Supplementation Trials
- Vitamin B12 and Cyanide
- Cyanocobalamin and Kidney Disease
Measuring B12 Status
- Should I Get My B12 Status Tested?
Plant and Intestinal Sources
- 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)
- Various Seaweeds: Dulse Warrants Further Study
- Coccolithophorid Algae
- A Case of False Reporting on the Benefit of Seaweed and Fermented Foods
- Genmai-Saishoku Paradox?
- German Whole Foods Vegans Consuming Nori and Mushrooms
- Soil and Organic Produce as a B12 Source for Vegans
- Intestinal Bacteria as a Vitamin B12 Source
- Overt B12 Deficiency—Nerve Damage and Anemia
- Ways to Get B12 Deficiency
- Early, Noticeable Symptoms of Overt B12 Deficiency
- Other Symptoms of Overt B12 Deficiency
- Neurological Symptoms
- Theories of How B12 Deficiency Causes Nerve Damage
- When Is It Time to Call a Doctor?
- Homocysteine and Mild B12 Deficiency in Vegans
The B12 Molecule
- Vitamin B12 Analogues
- Active and Inactive Analogues
- B12 in Animal Foods
- Inactive Analogues: Worse than Useless
- Weeding Out Inactive Analogues
- Vitamin B12 Absorption
- Digestion & Absorption of Protein-Bound B12
- Digestion & Absorption of Unbound B12
- Enterohepatic Circulation
- Transport in the Blood
- Pernicious Anemia
- Coenzyme Functions
B12 Status of Vegans
- B12 Status of Vegan Infants and Toddlers
- Infancy: A Critical Time
- B12 in Breast Milk of Vegans
- Infants of Vegan Mothers Who Do Not Use B12 Supplements
- Black Hebrews
- Correction of B12 Deficiency in Infants
- Vegan Infants Taking B12 Supplements
- B12 Deficiency Cases in Vegan Infants and Toddlers
- B12 Status of Vegan Children and Teenagers
- Vegan Children and Teenagers Supplementing with B12
- Vegan Children and Teenagers Not Supplementing with B12
- B12 Status of Vegan Adults
- Polish Clinical Trial (2012)
- EPIC-Oxford (2001 & 2010)
- Studies on Adult Vegans Not Supplementing with B12
- Vegans Taking B12 Supplements
- B12 Status of Older Vegetarians
- B12 Status of Raw Foodist Vegans
- Letter from a Raw Foodist Vegan
- Hallelujah Acres Diet
- Living Food Eaters in Finland
- Natural Hygiene Society Conference
- B12 Status of Macrobiotic Vegetarians
- The Macrobiotic Diet
- Macrobiotic Adults
- Macrobiotic Children
- Macrobiotic Infants
- Macrobiotic Breast Milk
- B12 Status of Lacto-Ovo Vegetarians
- Individual Cases of B12 Deficiency in Vegans
- Immerman—The Exception