The more frequent source of vitamin B-12 in association with plant food is external contamination with bacteria, often of fecal origin...

The fact that stool vitamin B-12 can be important in human vitamin B-12 economy was delineated by James Halsted (11) working with Iranian vegans who did not get vitamin B-12 deficiency... Halsted went to Iran and found that they grew their vegetables in night soil (human manure). The vegetables were eaten without being carefully washed and the amount of retained vitamin B-12 from the manure-rich soil was adequate to prevent vitamin B-12 deficiency.

Mozafar [1994] grew soybeans, barley, and spinach on three kinds of soils--unenriched soil (control), soil fertilized with raw, dried cow dung, and soil enriched with vitamin B-12. The discussion of Mozafar [1994] in this paper will omit the results from soil enriched with B-12, as it is not an economically feasible agricultural practice at present.

Vitamin B-12 levels were measured using "radioisotope dilution" [Mozafar 1994, p. 307], also called protein-binding. This assay claims a high resolution in distinguishing between true B-12 and analogues.

Plants may absorb B-12 from the soil. Mozafar [1994, pp. 307, 309-310] claims:

[M]ost, if not all, of the B-12 in the plant may be in the free form...

Considering the reports that plant roots and leaves can absorb the relatively large molecules of B-12 from nutrient solutions and transport them to other plant parts (Mozafar and Oertli 1992a) and the belief that plants cannot synthesize this vitamin (Friedrich, 1987; Lehninger, 1977; Smith, 1960), it seems that the observed increase in the concentration of B-12 in barley seeds and spinach leaves fertilized with cow dung is mostly (if not fully) due to the uptake of this vitamin by the roots from the soil and not due to superficial contamination or an increased synthesis within the plant.

A later paper by Mozafar--i.e., Mozafar [1997, p. 51]--reports that very little is known about the absorption of B-12 analogues by plants. Note also that the second part of the above quote contradicts the claim by Herbert that B-12 is usually found primarily externally in plants. (The claim by Herbert may be outdated/incorrect; see Mozafar and Oertli [1992] for discussion of their research that shows soybean roots are able to absorb B-12, and the vitamin can be transported within the plant.)

B-12 found in tested plant foods. Mozafar found that the levels of B-12 in barley and spinach grown in untreated (control) soil versus soil treated with cow dung were significantly different. However, the B-12 levels of soybeans were not significantly different for the two soil types.

The B-12 measurements in Mozafar [1994] are frankly hard to interpret as-is. That is, the measurement unit utilized, i.e., nanograms of B-12 per gram of plant food, dry weight, is not meaningful to most readers. To help readers understand the Mozafar results, a part of the results are used below to estimate the amount of each plant food (by itself) needed to get 2 mcg of B-12 per day. The last 2 columns in the table below are the most important--they show the estimated weight (in kilograms and in pounds) of raw plant foods required to satisfy daily B-12 requirements.

*NOTE: Sprouting applies to the figures for soybeans and barley; spinach is eaten as-is.

See Appendix 5 for assumptions and technical notes regarding table derivation.

Soybeans. Soybeans in their crude form are inedible, and need sprouting or cooking to be rendered edible. Many raw-fooders would challenge the idea that even raw, sprouted soybeans are actually that edible, however, as the flavor is--how to say it--"intensely awful." At any rate, to satisfy B-12 requirements one must eat 2.64-4.78 kg, or 5.81-10.52 pounds of soybean sprouts, per day, to meet B-12 requirements. It is very difficult/nearly impossible to eat that much bulk on a regular basis. The crude beans (0.75-1.37 kg) can be cooked, and the bulk is more manageable, but it is not clear how much extra one would need to eat to adjust for B-12 losses in cooking.

Barley kernels. Barley kernels in their crude form are inedible. While not 100% certain, it appears Mozafar tested unhulled barley, which has a tough hull (with sharp edges when chewed) that makes eating it raw very difficult, even when sprouted. The amounts of barley required are lower than for soybeans; in sprouted form, the estimate is 0.49-1.70 kg, or 1.07-3.74 pounds. However, the reality of the extremely tough hull on barley makes eating even 0.49 kg (1.07 pounds) per day a difficult and unpleasant task. The 0.24-0.85 kg (0.53-1.87 pounds) of crude barley kernels, if hulled and cooked, are easy to consume. Again, the problem arises in that one needs accurate data on B-12 losses in cooking to know how much extra to eat to compensate for loss of B-12 in cooking.

Spinach. Here 1.33-3.44 kg (2.94-7.57 pounds) are required. The amounts are within the range of possibility for a person to eat, though it would be difficult (bulk--multiple meals required). The problem, of course, is that a reliable supply of manured spinach is not available to most people, and the weights required of control (unmanured) spinach--3.44 kg or 7.57 pounds--are far too high, again, i.e, yet another bulk problem. It would be extremely difficult to eat that weight of greens in a day.

• B-12 levels in soil highly variable. The table in Mozafar [1994, Table 3, p. 309] indicates that B-12 levels in soil can vary widely. Accordingly, it would be unwise to assume that a particular soil will supply levels of B-12 to plants that are adequate for human nutritional needs.

• B-12 losses in shipping and processing? Mozafar analyzed the plant foods at the location where they were grown, just after harvest. Most consumers buy their foods from markets, and the food has been processed and shipped. This raises the question of whether, and how much, post-harvest processing and shipping can change the B-12 levels in foods. Similar questions apply to types of cooking and food processing.

• Legal risks from use of raw manure. The study used raw animal manure; owing to the liability risks (E. coli) of raw manure, the research should be repeated with composted manure. The use of raw, dry cow dung as a soil amendment is uncommon (nowadays) in farming as it can introduce weed seeds.

• The use of manure is not universal, even in organic gardening; it is not the case that "organic = manured" or even "organic = composted." Some organic farmers prefer to simply use heavy mulches, with no manure or compost.

• Some vegan purists reject the use of animal manure. The term used for such gardening is "veganic."

• Inasmuch as some vegans condemn the use of manure in farming, the information that the only possible "natural" way to get B-12 in the usual plant foods is via the use of manure--an animal product--as fertilizer provides yet another contradiction/irony in veganism. Of course, some might reply that human manure can be used instead. Indeed it can, but if cow dung is abhorrent to vegan purists because it is an "animal product," then is human manure an "animal product" as well? What about human manure from meat-eaters?

• Per Mozafar, sewage sludge is very high in B-12, but organic food advocates oppose the use of sewage sludge because of possible heavy metal contamination. (The underlying point here is that sewage sludge might be used--in very small quantities, as a compost additive--to inoculate soils with B-12.)

• Raw human feces, aka "night soil," is high in B-12. However, its use in farming raises the risk of parasites, E. coli, and potential liability lawsuits aimed at farmers. It is not a feasible soil additive for farms, at present.

• The Mozafar [1994] paper is considered controversial by some veg*n nutritionists. For comments, see Craig [1997] as cited in Mozafar [1997], and Mozafar [1997] for reply.

• Possible exaggerations by raw/veg*n advocates. Given that Mozafar [1994] is only one (limited) study, that it did not test wild foods, fruits or nuts, roots or tubers, then to claim that it "proves" plant foods are adequate sources for B-12 would be an exaggeration. (Mozafar makes no such claims; the claim is occasionally made by raw vegan advocates).

Chimps and other apes have been observed engaging in geophagy, i.e., eating dirt, though the predominant hypothesis is that chimp geophagy is done to ingest clay that absorbs excess plant tannins in the GI tract (and not as a B-12 source).

Mozafar [1994] reports 14 mcg B-12 per kg of soil. If we assume this is all true B-12 and no analogues (highly unlikely), it implies a daily intake of ~143 g (0.31 pounds) of soil daily to satisfy B-12 requirements. Such an intake is obviously not feasible. Note that Mozafar lists B-12 values for soil from other studies as well (Table 3, p. 309, Mozafar [1994]). However, many of the studies cited are old and thus the assay methods used should be checked. Mozafar reports that soil is one of the richest sources of B-12, but that there is no information available on the level of analogues vs. true B-12 in soil.

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(Feasible Vitamin B-12 Sources in Evolution / Mercury and B-12)

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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?

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