by Jack Norris, RD
Vitamin B12 is the most important nutrient for vegans to be aware of. B12 is found in meat, dairy, and eggs. In contrast, there are no reliable plant sources of B12 other than fortified foods. Luckily, B12 is made by bacteria and so doesn’t need to be obtained from animal products.
It’s fairly easy for most vegans to obtain a source of B12, and taking it on a regular basis will provide someone with a B12 status equal to or superior to people who rely on animal products for B12. 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. This and many other Individual Cases of B12 Deficiency in Vegans, and a great deal of other research, has led to the overwhelming consensus in the mainstream nutrition community and vegan health professionals that vitamin B12 fortified foods or supplements are necessary for the optimal health of vegans. I’ve known many vegans who neglected B12 and subsequently experienced fatigue and temporary neuropathy that resolved upon obtaining a reliable source.
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 vitamin 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:
- Vitamin B12 intake requirements are listed in Daily Needs.
- Vegan Sources
- Can a Natural Diet Require Supplements?
For other opinions, 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—it includes every important study on vegans published since 1980.
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
Measuring B12 Status
- Should I Get My B12 Status Tested?
- 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
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
- Vitamin B12 and Nonhuman Animals
Vitamin B12 Supplements
- Elevated Vitamin B12 Levels and Mortality
- PREVEND Raises Concern
- Negative Outcomes in Vitamin B12 Supplementation Trials
- Vitamin B12 and Cyanide
- Cyanocobalamin and Kidney Disease
- Methylcobalamin and Adenosylcobalamin
- 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
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