Prior to agriculture, there were no domesticated crops or herds of domesticated animals. Consequently, there was no deliberate manuring of food crops--which is an agricultural practice, not a hunter-gatherer practice. Of course, some wild plants will--by chance or other reasons--receive limited amounts of wild animal manure. However, there is insufficient evidence to support a claim that such incidental, occasional manuring (of wild plants) would provide a reliable source of adequate B-12 (particularly in light of the extremely high bulk of unmanured plant foods required to meet B-12 requirements).

Potentially feasible plant B-12 sources--legumes and grains--not available to hunter-gatherers. Note that Mozafar found higher levels of B-12 in soybeans (a legume) and barley (a grain) than in spinach. Prior to the development of agriculture, such items (legumes, grains) would have been available only in very limited quantities to hunter-gatherer tribes.

Further, prior to the development of cooking technology (stone ovens and/or pottery), it would not be possible to cook (or sprout) significant quantities of such foods. (Think of the difficult task of roasting, or sprouting--without implements or containers--a pile of loose, small seeds.) Pottery is also required for cooking most vegetables other than tubers or hard squashes. That means early humans, if they were strictly vegan, would need to eat huge amounts of raw greens per day to satisfy B-12 requirements (and even larger amounts to meet minimal calorie requirements; see The Calorie Paradox of Raw Veganism for more details). The seasonal limits on the availability of greens (and other plant foods) in temperate climates, combined with the large amounts required, further disqualifies greens as a feasible B-12 source.

Fauna (animal foods) the consistent B-12 source in evolution. Accordingly, the only reliable/feasible sources of B-12, pre-agriculture, were coprophagy and the consumption of animal products. There is ample evidence of consumption of animal products in pre-agricultural times, but no evidence that coprophagy was ever a common practice. That leaves animal products (including insects) as the only reliable B-12 source in pre-agricultural times, and by implication suggests (if further evidence were needed beyond that already existing about prehistoric peoples) that there never existed any strictly vegan hunter-gatherers, as B-12 is an essential nutrient. (This also suggests that strict fruitarian/vegan diets were never a factor in human evolution.)

• Apparently not a peer-reviewed theory. The theory reportedly appears in an article in a periodical called Heavy Metal Bulletin (1995, not in the reference list for this paper). A search of several university libraries failed to find the periodical, suggesting an incorrect title, or, perhaps, that the periodical is not a scientific, peer-reviewed journal. Note that the comments here are based on a poorly written article (by a fruitarian extremist) that discusses the theory. (The article included what is claimed to be the reference list from the original article.)

• Defective reference list. A check of the articles allegedly in the reference list for the original theory article finds that at least 4 articles were either cited incorrectly or apparently do not exist. The net effect of such irregularities is to raise serious questions regarding the paper's validity.

• Evidence of non-human primates raises doubts about theory. The fact that wild primates (who have no silver-mercury amalgams in their mouths) who are fed vegetarian diets in captivity become B-12 deficient (references cited above) suggests that B-12 deficiency is real; while the "B-12/mercury hypothesis" is, at best, unproven.

• Pardridge [1976] showed that inorganic mercury interfered with brain uptake of certain amino acids, but his research did not test trans-cobalamin, methionine, or homocysteine--the proteins/amino acids involved in B-12 metabolism in the brain.

• Selenium/mercury association (in the brain) confirmed. Friberg and Mottett [1989], in their review article, suggest, and Bjorkman et al. [1995] confirm, a statistical relationship between inorganic mercury in the brain and selenium (not cobalt). This does not disprove the cobalt hypothesis, but it provides an alternate and proven hypothesis (whereas the cobalt hypothesis is unproven). Additionally, selenium is far more common than cobalt, which raises the question whether it might prevent potential B-12/mercury oxidation by "out-competing" the cobalt for any inorganic mercury present.

• Mercury chelated by tryptophan, a common amino acid. Pardridge [1976] reports that inorganic mercury is chelated by tryptophan, a common amino acid. This suggests that high-protein diets might provide limited protection from inorganic mercury uptake. (Ironically, the fruitarian extremist touting the vague B-12/mercury hypothesis advocates very low-protein diets.)

• Kanazawa and Herbert [1982] report that the B-12 in the human brain is nearly all true B-12; there are only trace amounts of B-12 analogues. This raises the interesting question of whether a mercury/B-12 compound could cross the blood/brain barrier, or if it would be rejected as an analogue. Note that this information is based on a very small sample, and must be interpreted with caution.

• Is there enough mercury to "starve" the brain of B-12, long-term? Given the information in the three preceding paragraphs, one wonders if dental fillings could provide, over a long period of time, enough mercury to react with all the available tryptophan, selenium, and cobalt? Given that tryptophan and selenium are relatively "common" (at least in comparison to cobalt), and that the amounts of mercury released by dental amalgam are extremely small, such a hypothesis seems dubious and would require credible evidence that has been published in a peer-reviewed, scientific journal.

• Implication: Rely only on legitimate scientific information on B-12. For a legitimate scientific introduction to cobalamin metabolism, readers are encouraged to consult Tefferi and Pruthi [1994], which was consulted in the preparation of these remarks. An additional legitimate resource regarding B-12 deficiency and its biochemical basis is Cooper and Rosenblatt [1987].

Attempts to reverse burden of proof. Finally, this exercise also illustrates one of the bad habits of the raw/veg*n movement: adopt an unproven theory or claim, then aggressively demand that others disprove it. Such an approach is an attempt to reverse the burden of proof, and the purveyors of such untested hypotheses should not be so easily allowed to get away with such assaults against reason.

Unfortunately, many in such circles cannot distinguish between Victor Herbert the politician and Victor Herbert the research scientist. Herbert is one of the top researchers in the B-12 area and has a lengthy list of publications in scientific/professional journals. That record--extensive publication in refereed scientific journals--is a record that the anti-Victor Herbert lobby cannot match. Accordingly, I encourage you to evaluate his research on its technical merits, and not to be swayed by emotional or political sentiments.

• Vitamin B-12 is an essential vitamin for which the only reliable sources are fauna (animal foods) and coprophagy (should you freely choose to engage in it, which is most definitely not recommended). There is no evidence to support the idea that coprophagy is a natural human behavior, while there is extensive evidence that humans have consumed animal foods since the inception of the (human) species.

• Indirect coprophagy--eating plants fertilized with raw excrement--might provide adequate B-12, although the supporting evidence for this is very limited at present. As well, the use of raw excrement in farming poses risks--of parasites and disease for the consumer--and liability lawsuits aimed at the farmer. Indirect coprophagy is not a feasible option at present.

• The nutritional requirement for B-12, coupled with the lack of ability to assimilate B-12 at the site synthesized by bacteria in the human body (the colon), and the fact that plant foods are not reliable sources of B-12, provides evidence of apparent long consumption (and evolutionary adaptation) to animal foods in the human diet.

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SEE REFERENCE LIST

SEE TABLE OF CONTENTS FOR:
PART 1 PART 2 PART 3 PART 4 PART 5 PART 6 PART 7 PART 8 PART 9

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GO TO PART 1 - Brief Overview: What is the Relevance of Comparative Anatomical and Physiological "Proofs"?

GO TO PART 2 - Looking at Ape Diets: Myths, Realities, and Rationalizations

GO TO PART 3 - The Fossil-Record Evidence about Human Diet

GO TO PART 4 - Intelligence, Evolution of the Human Brain, and Diet

GO TO PART 5 - Limitations on Comparative Dietary Proofs

GO TO PART 6 - What Comparative Anatomy Does and Doesn't Tell Us about Human Diet

GO TO PART 7 - Insights about Human Nutrition & Digestion from Comparative Physiology

GO TO PART 8 - Further Issues in the Debate over Omnivorous vs. Vegetarian Diets

GO TO PART 9 - Conclusions: The End, or The Beginning of a New Approach to Your Diet?

Back to Research-Based Appraisals of Alternative Diet Lore