B12 in Nodules from Legumes

From PubMed:

http://www.pubmedcentral.nih.gov/pic...6&blobtype=pdf (NB: the link is to a .pdf-file, size 2.5 mb).

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It is generally recognized that vitamin B12 is synthesized only by microorganisms. The vitamin has been identified in root nodules of leguminous plants and in roots of nonleguminous species, but in these cases the synthesis has been attributed to the nitrogen-fixing bacteria in nodules and to soil microorganisms respectively. Even though cobalt has been recognized as a micronutrient for animals and certain microorganisms, until recently there has been no conclusive evidence of its essentiality for higher plants.

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According to WJ Robbins et al.1 (1950, New York Botanical Gardens*), B12 (the relationship between active/inactive B12 is unknown) were found in the roots of plants (0.0002-0.01 µg B12/g of fresh material).

Normally, B12 is listed pr 100g, or even pr kg (1000g).

0.0002-0.01 µg B12/g equals:
0.02-1 µg B12/100g, or
0.2 - 10 mcg/1000g.

These results show that the roots of these plants contains almost the same levels B12 relative to their weight that the amount of B12 found in soil. Studies performed by A. Mozafar in 1994 has shown that soil contains 5-9 mcg B12/1000g synthetically fertilized soil, and 10-14 mcg B12/1000g soil that has been treated with organic fertilizer once every 5 years.


B12 was also found in the stems of these plants, but - in this study - B12 was generally not found in leaves and fruit.


*Robbins WJ, Hervey A, Stebbins ME. Studies on Euglena and vitamin B12. Science 1950(Oct 20):455.

More info here: http://www.pnas.org/cgi/reprint/47/1/24.pdf?ck=nck

Here are some numbers from that article.

The 'apparent' vitamin B12 content was assayed by the Lactobacillus leichmannii (ATCC 7830) method, and the 'true' vitamin B12 content was determined using Ochromonas malhamensis by the method outlined by J. E. Ford. (Ford, J. E., Brit. J. Nutrition, 7, 299 (1953).).

Using the first method, they found that the levels of B12 in the soy bean root nodules were 18 mcg/g - or 1800 mcg pr. 100 g.

Both these results were achieved when cobalt was not added manually - adding extra cobalt resulted in much higher numbers.

Using the method to measure the true vitamin B12 content, they found 0.33 mcg B12 pr gram, or 100 mcg true B12 pr 100 g. That's a very high number, and means that in order to consume eg. 0.5 mcg true B12, only 0.5 g soy bean root nodules would be needed. The ratio between true B12 and pseudo-B12 is 1:54. As I've mentioned in other threads, there is disagreement re. how the presence of pseudo-B12 affects our ability to absorb active B12.

Note that I mention intake, and not absorption B12. Dr. Victor Herbert used to claim that only half of the consumed B12 is absorbed, but we have more detailed info about the ratio between absorption/consumption today. He also said that "well washed" plant foods contain no B12 except for trace amounts in some rhibozium-bacteria containing root nodules - we know today that this is wrong, but his statements stopped further investigations about B12 levels in plants for a while. The numbers in the .pdf-file above provides some more info about the actual levels of B12 in root nodules.

If this 'true' B12 in the root nodules actually helps to keep MMA and homocysteine levels healthy, it seems that only a few grams of these root nodules would be needed.

Vitamin B12 Analogues in Non-legume Root Nodules

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IT has been shown1–4 that cobalt must be available for legume nodules to supply fixed nitrogen efficiently to the plant bearing them. It has also been shown that in such nodules cobalt is elaborated into the form of vitamin B12 analogues. Thus Levin et al. 5, using Ochromonas and Euglena assays, reported that appreciable (though not actually stated) amounts of the vitamin were present in nodules of lucerne, clover and pea, very much smaller quantities being detected in the roots of the same plants.

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This is confusing, because the term analogues are often used about inactive analogues, but by others, all corrinoids* (including all cobalamins) are considered "B12 analogues". Cobalamins are not always useable cobalamin.

*A 'corrinoid' is a molecule that contains a corrin nucleus. The core in cobalamin is a cobalt atom. There are several types of cobalamin (cyancobalamin, methylcobalamin etc).

In other words, I don't know if this text refers to 'inactive B12' or just use the term 'analogue' since it's describing a cobalamin.

So... can the information above be interpreted as if the root nodules in lucerne, clover and peas contain B12 that humans can use? Not necessarily.

B12 Coenzyme Content of the Nodules from Legumes, Alder and of Rhizobium meliloti

An excerpt:

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The vitamin B12 content of root nodules from soybean plants is positively correlated with the cobalt supply in the nutrient medium1, suggesting that an important role of this element in nodule metabolism is related to that of the vitamin.

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