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Vitamin B12: Are You Getting It?

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B12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods

Summary: The only plant foods which have been tested for B12 activity using the gold standard of lowering MMA levels in humans are dried and raw nori from Japan. Dried nori made MMA status worse, indicating that it can reduce B12 status and can possibly harm people who are B12-deficient. Raw nori kept MMA levels about the same, indicating that it didn't harm B12 status, but it did not help either.

No food in Europe or the U.S. has been tested for lowering MMA levels. Thus, the discussion about whether Western vegans can get B12 from plant foods can, and probably should, end here (until proper research is conducted). Because so many plant foods have failed other tests that do not measure up to the MMA lowering test, and because there are so many false rumors being passed around, the studies of B12 in plant foods are examined in detail below.

Of all the foods studied below, only tempeh in Indonesia or Thailand, dulse, Chlorella, raw nori, and coccolithophorid algae warrant much further attention for providing B12. Unless these foods are shown consistently to correct B12 deficiency, vegans should not rely on them as a B12 source.

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Contents of B12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods

Introduction

It would be great to find a reliable plant source of B12 for vegans. One might get the opposite impression given my level of critique of some of these studies. My skepticism is only due to the potential harm from relying on a food that contains inactive B12 analogues which can make a B12 deficiency even worse.

There has been a long history of misconceptions about which, if any, plant foods are sources of B12. Much of this stems from the methods of measuring B12 analogues. Other confusion stems from bacterial contamination that occurs in some foods but not others. Please see Measuring B12 in Plant Foods: Why the Confusion? for an explanation of the methods for for measuring B12 analogues in plant foods.

Unlike animals, most, if not all, plants have no B12 requirement for any function, and therefore have no active mechanisms to produce or store B12. Many seaweeds have been shown to have B12 analogues. (Note: Most seaweeds are algae, which are technically not plants.) It is not clear whether the algae make the B12 analogues or whether they absorb the B12 analogues from their environment.1

During the 1970s, two enzymes in plants (potatoes and bean seedlings) were found to respond to the addition of adenosylcobalamin2,3 (a co-enzyme form of B12). One explanation is that adenosylcobalamin provides some factor that is usable by these enzymes, but that adenosylcobalamin is not required by these plants for growth. Thus far, these plants have not been shown to counteract B12 deficiency symptoms (though I am not aware of any well-designed attempts as it is assumed that they do not contain B12). It is probably safe to assume that many vegans who have developed severe B12 deficiency ate potatoes and beans.

There are some rumors, though no evidence of which I am aware, that if you let organic produce, such as carrots, sit at room temperature for a few hours, bacteria on the surface of the carrots will produce B12. For this to happen, specific species of bacteria would be required, as would cobalt. Until there is research showing that such a method can lower MMA levels, such produce should not be considered to provide B12.

Notes for Introduction
1. Watanabe F, Katsura H, Takenaka S, Fujita T, Abe K, Tamura Y, Nakatsuka T, Nakano Y. Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets. J Agric Food Chem. 1999 Nov;47(11):4736-41.
2. Poston JM. Coenzyme B12-dependent enzymes in potatoes: leucine 2,3-aminomutase and methylmalonyl-coa mutase. Phytochemistry. 1978;17:401-402.
3. Poston JM. Leucine 2,3-aminomutase: a cobalamin-dependent enzyme present in bean seedlings. Science. 1977;195:301-302.

Plant Foods with Practically No Detectable B12 Analogue

Various studies have tested the foods in the table below for B12 analogues and found none. To my knowledge, other than in Mozafar's studies (below) in which B12 and cow dung were carefully added to the soil of potted plants, no published study has shown any B12 analogues in any of these foods.

Foods with No Detectable B12 Analogue
amesake rice1 barley miso1 miso2 natto2
rice miso1 shoyu1 tamari1 umeboshi prunes1
various fruits, vegetables, nuts,
seeds, & grains2 		 

The following table shows the B12 analogue content of various plant foods:

B12 Analogue Content (µg/30 g) of Various Foods
Country Netherlands1 Thailand2,3
Assay IF IF or R-proteinA
fermented soybean   0.15
barley malt syrup
sourdough bread
parsley
shiitake mushrooms		 .006-0.1
Only info given 		 
dried fermented soybean   0.01
tofu ND 0.02
soybean paste   0.03
soy sauce   .01B
A - Used an assay method by Lau et al.57 (1965) which uses R-protein or IF
B - µg/30 ml
IF - Intrinsic Factory Assay
ND - None Detected

As you can see, there are very small amounts, if any. Since the amounts are so small, any inactive analogues should not significantly interfere with an individual's active B12 from other sources, and if the analogue is active B12, it will not provide much. Thus, these foods should neither add to, nor detract from, a vegan's B12 status.

Notes for Plant Foods with Practically No Detectable B12 Analogue
1. van den Berg H, Dagnelie PC, van Staveren WA. Vitamin B12 and Seaweed. Lancet Jan 30, 1988.
2. Areekul S, Churdchu K, Pungpapong V. Serum folate, vitamin B12 and vitamin B12 binding protein in vegetarians. J Med Assoc Thai 1988 May;71(5):253-7.
3.Areekul S, Pattanamatum S, Cheeramakara C, Churdchue K, Nitayapabskoon S, Chongsanguan M. The source and content of vitamin B12 in the tempehs. J Med Assoc Thai 1990 Mar;73(3):152-6.

Tempeh

For a long time, tempeh has been said to contain B12. Table A.3 shows the results of measuring B12 analogue in various tempehs.

B12 Analogue Content (µg/30 g) of Tempehs
Country Netherlands1 USA2 Indonesia3,4
Assay IF IF IF or R-proteinA
tempeh ND .02C .054-1.2B
A - Used an assay method by Lau et al.57 (1965) which uses R-protein or IF
B - 10 commercial tempeh samples purchased from various markets in Jakarta, Indonesia
C - Cooked for 60 minutes
IF - Intrinsic Factory
ND - None Detected

The studies in the USA and in The Netherlands showed little to no B12 analogue.

In contrast, Areekul et al.4 (1990, Indonesia/Thailand) found more significant amounts of B12 analogue. Tempeh production requires molds belonging to the genus Rhizopus. These were found not to produce B12 analogues in Areekul et al's study. Rather, a bacterium, identified as Klebsiella pneumoniae, was isolated from the commercial tempeh starter and determined to be the B12 analogue source. This confirmed Albert et al.'s5 (1980) finding that the Klebsiella genera could produce B12 analogues. In Albert's study, the analogue was thought to be active B12. Whether the analogues found by Areekul et al. were the same as in Albert's study is not known. Given that K. pneumoniae is not required for tempeh production, we can conclude that the B12 analogue found in the tempeh's in Indonesia were due to bacterial contamination (though apparently common there). Tempeh in Europe and the U.S. cannot be relied on as a source of B12. Until tempeh in Indonesia are shown to reduce MMA levels, it should not be relied upon there, either.

Notes for Tempeh
1. van den Berg H, Dagnelie PC, van Staveren WA. Vitamin B12 and Seaweed. Lancet Jan 30, 1988.
2. Specker BL, Miller D, Norman EJ, Greene H, Hayes KC. Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B-12. Am J Clin Nutr 1988 Jan;47(1):89-92.
3. Areekul S, Churdchu K, Pungpapong V. Serum folate, vitamin B12 and vitamin B12 binding protein in vegetarians. J Med Assoc Thai 1988 May;71(5):253-7.
4. Areekul S, Pattanamatum S, Cheeramakara C, Churdchue K, Nitayapabskoon S, Chongsanguan M. The source and content of vitamin B12 in the tempehs. J Med Assoc Thai 1990 Mar;73(3):152-6.
5. Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human small intestinal bacteria. Nature 1980;283(Feb 21):781-2.

Seaweeds

Soil and Organic Produce as a B12 Source for Vegans

It is common in vegan circles to hear that if your produce has soil on it and you do not wash the produce before eating it, bacteria that lives in the soil and on the produce will provide B12. It is also claimed that in today's world, our food supply is very sanitized whereas in the past, vegan humans would have received plenty of B12 from the unsanitized produce. What is the evidence for these claims?

Previous section: Measuring B12: Why the Confusion?
Next section: Are Intestinal Bacteria a Reliable Source of B12?
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Last Updated: May 09, 2009