Vitamin B12: Are You Getting It?

by Jack Norris, Registered Dietitian


For the last few months, I was feeling sluggish, had to lie down a couple of times a day, found it difficult to work evenings and to exercise for long periods. Under Michael Klaper, MD's guidance, I was taking protein powder, creatine, testosterone, nystatin, etc., all to no avail. I was taking nutritional yeast every day, so I knew it wasn't B12 deficiency. Then, one day, I came across your B12 article by sheer accident. I wasn't going to read the whole thing, but I glanced through it and was struck by your insistence that none of the usual sources are adequate. I still didn't believe it, but I had some old B12 pills in the fridge, so I popped one. The effect was almost immediate and remarkable. I have been taking them almost every day, my stamina and energy level are up, and I feel middle-aged again instead of a tired old man.

- Alex Hershaft, PhD, President of FARM


Vitamin B12 is a complicated vitamin with a unique absorption mechanism and a number of inactive analogues (molecules that appear to be active B12, but actually are not) that possibly interfere with its function. Vitamin B12 is generally found in all animal foods (except honey). Contrary to the many rumors, there are no reliable, unfortified plant sources of vitamin B12, including tempeh, seaweeds, and organic produce. One of the earliest studies conducted on vegans, from the U.K. in 1955, described significant vitamin B12 deficiency in the vegans with some suffering from nerve damage and dementia. This, as well as many case studies since then of vitamin B12 deficiency in vegans, and a great deal of other evidence detailed here, has led to the overwhelming consensus in the mainstream nutrition community, as well as among vegan health professionals, that vitamin B12 fortified foods or supplements are necessary for the optimal health of vegans, and even vegetarians in many cases. Luckily, vitamin B12 is made by bacteria such that it does not need to be obtained from animal products.

Despite the overwhelming evidence that vegans without a reliable source of vitamin B12 are likely harming their health, some vegan advocates still believe that "plant foods provide all the nutrients necessary for optimal health," and do not address vitamin B12 when promoting the vegan diet. Other advocates acknowledge the need for B12, but only as an afterthought. And still others emphasize that humans need only small amounts of B12 and that it can be stored in the body for years.

While true that, at the time they become vegan, some people have enough B12 stored in their liver to prevent overt B12 deficiency for many years, people often misinterpret this to mean that you only need to consume a tiny amount once every few years. Actually, to build up such stores, it takes years of consuming B12 beyond one's daily needs (unless you are using supplements which can build up stores more quickly). Some people do not have large enough stores of B12 to be relied upon for optimal health even for short periods.

This article is a thorough review of the scientific literature about vitamin B12 and the vegan diet, including every relevant study on vegans and vitamin B12 published since 1980. Vegan advocates who may otherwise not be interested in the details of vitamin B12 are encouraged to read the Recommendations and Can a Natural Diet Require Supplements?

Overt B12 Deficiency

B12 protects the nervous system. Without it, permanent damage can result (e.g., blindness, deafness, dementia). Fatigue, and tingling in the hands or feet, can be early signs of deficiency.

Vitamin B12, like folate (aka folic acid), is needed to help red blood cells divide. In some cases, vegans may get so much folate that even with B12 deficiency, their blood cells continue to divide properly. In other cases, their blood cells will fail to divide properly and they will become fatigued and suffer from macrocytic (aka megaloblastic) anemia.

Mild B12 Deficiency

Homocysteine is a byproduct of protein metabolism. Elevated homocysteine levels are linked with increased risks of heart disease and stroke. From 1999 to 2003, there were many studies comparing the homocysteine levels of vegans and vegetarians who do not supplement their diet with vitamin B12 to those of non-vegetarians (more info). In every study, the vegans or vegetarians had higher homocysteine levels than the meat-eaters and in the range associated with heart disease and stroke.

In contrast, one study compared vegans who supplemented with vitamin B12 (an average of 5.6 mcg/day) and their homocysteine levels were well within the healthy range.

If you have been a typical meat eater for most of your life, your body should have stored enough B12 to prevent overt deficiency for a number of years. However, B12 stores cannot be relied on to keep homocysteine levels in check for very long.

Open Letter from Health Professionals & Vegan Organizations

Other opinions by vegan movement leaders and health professionals on the need for vitamin B12:

What Every Vegan Should Know about Vitamin B12

Table of Contents

  1. Vitamin B12 Recommendations
  2. Vegan Sources
  3. Can a Natural Diet Require Supplements?


  1. Overt B12 Deficiency - Nerve Damage and Anemia
  2. Mild B12 Deficiency - Cardiovascular Disease | Dementia | Birth Defects | Bone Mineral Density
  3. Small Amounts of Animal Products Do Not Cure B12 Deficiency

The B12 Molecule

  1. Analogues
  2. Digestion, Absorption, and Transport
  3. Coenzyme Functions


  1. Blood B12 Levels: Not Reliable
  2. Should I Get My B12 Status Tested?

B12 Status

  1. Vegans Infants & Toddlers
  2. Vegan Children & Teenagers
  3. Vegan Adults
  4. Elderly Vegetarians
  5. Raw Foodist Vegans
  6. Macrobiotics
  7. Lacto-Ovo Vegetarians
  8. Individual Cases of Deficiency
  9. Immerman - The Exception

Plant & Intestinal Sources

  1. Measuring B12: Why the Confusion?
  2. B12 in Plant Foods
  3. Are Intestinal Bacteria a Reliable Source of B12?
  4. B12 and Non-Human Animals


  1. How Recommendations were Formulated
  2. Side Effects of Vitamin B12 Supplements
  3. People Over Age 50
  4. People Who Should Not Take the Cyanocobalamin Form of B12
  5. Smokers and Cyanocobalamin
  6. Methylcobalamin & Adenosylcobalamin
  7. S-adenosylmethionine (SAMe)
  8. Ways to Get B12 Deficiency
  9. Elevated Serum B12 and Increased Risk of Disease
  10. Conditions That Increase B12 Levels
  11. B12-Related Laboratory Values
  12. Plant Sources of Folate
  13. Figure: Methionine-Homocysteine-Folate-B12 Cycle