Evidence-Based Nutrient Recommendations

Immerman: The Exception

As of 2004, the lone peer-reviewed article that downplayed, rather than emphasized, the need for vegans to supplement their diets with B12 was by Immerman (Immerman, 1981). Immerman reviewed 13 case studies in which a vegan was found to have B12 deficiency. He lists a number of criteria which he claims must be used to determine a true B12 dietary deficiency versus a different problem such as:

  • Malabsorption via:
    • Inadequate protein, calories, or folate
    • Radiation, drugs and toxins (neomycin, colchicine, para-amino salicylic acid, alcohol)
    • Pancreatic tumor
    • Failure of the small intestine to contract and move food associated with bacterial overgrowth
    • Oral contraceptives
  • Increased excretion due to liver or kidney disease
  • Tobacco smoking
  • Vitamin B6 or iron deficiency

None of the case studies listed by Immerman met all of his criteria. He was particularly critical of the idea that a dietary B12 deficiency exists if B12 symptoms improve upon B12 injections rather than oral tablets. However, because the authors of earlier case studies were interested in helping the patients rather than proving whether vegans should take B12, they used injections, the common method of clearing up B12 deficiency quickly. The injections helped their patients.

Immerman says that low B12 levels should not be used to determine a B12 deficiency. By this criterion, he says “[I]t would be necessary to characterize not only most Western vegetarians but also much of the population of India and other Eastern countries as deficient; this is clearly unacceptable.” Numerous studies (presented here) show that much of the world’s vegetarian population who do not supplement with B12 could improve their B12 status resulting in health benefits.

Immerman says that cooking destroys significant amounts of B12 and that consuming primarily raw foods could increase one’s intake of B12. Other studies have shown that vegan raw foodists do not appear to have an advantage over other vegetarians.

Immerman states, “[M]any studies have found apparently adequate B12 status in individuals consuming [a vegetarian or vegan] diet, although the investigations in some of these studies have been incomplete. It must be concluded, therefore, that pure dietary B12 deficiency in all classes of vegetarians is the exception rather than the rule.”

Immerman was writing in 1981, before the great majority of the studies included in this article were published and before much was known about homocysteine. While it is true that the worst cases of B12 deficiency listed by Immerman were sometimes aggravated by other health problems, it seems likely that had these vegans been taking oral B12, the problems never would have become so severe, and in many cases, never would have occurred at all. In many of the cases, B12 deficiency was immediately cleared up through oral B12.

In the end, even Immerman suggests that vegetarians have their B12 levels checked every 4-5 years. It would be more prudent, and easier, to take B12 supplements or eat fortified foods. Why wait 4-5 years for a doctor to tell you what you should have been doing all along?

Analysis of Immerman’s Paper

A more rigorous analysis of Immerman’s paper appears online in the article Comparative Anatomy and Physiology Brought Up to Date, by Tom Billings at BeyondVeg.com.


Immerman AM. Vitamin B12 status on a vegetarian diet: A critical review. World Rev Nutr Diet. 1981;37:38-54.

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