I just read an interesting paper from March 2011 (sent my way by Dave of TheVegetarianSite.com). It was a cross-sectional study on semi-vegan, Buddhist nuns from Korea. The study was done by German researchers studying how the nuns’ B12, folate, and iron intakes were affecting their blood cell size (1).

The nuns’ blood cells appeared fine, indicating that either they were getting plenty of vitamin B12 for the purposes of their blood cells, or that they were getting enough folate to mask a B12 deficiency. I should also point out that there are two types of B12 deficiency – one that causes blood problems (which can be masked by high intakes of folate) and one that causes nerve problems (that cannot be masked by high folate intakes).

For me, the more interesting part of the paper was how strongly the researchers suggested that nori (also known as laver) is a reliable source of vitamin B12.

The semi-vegan Buddhists ate some dairy, but it was not very much according to their diet diaries (only 21 grams per day on average). If you assume they were drinking milk, 21 grams would be only about .1 µg of B12 per day. That is not enough to keep vitamin B12 levels at the 360 pmol/l that they averaged, indicating they either were eating more animal products than reported or were getting their B12 elsewhere, such as from nori.

The nuns ate 1.3 g of nori per day. According to previous studies, nori contains anywhere from about 1.5 to 20 µg of B12 analogue per 30 g. That would mean 1.3 g of nori would contain .05 to .6 µg. If we generously assume the nori had the very highest amount of B12 and add the .6 to the .1 µg from dairy products, you get .7 µg of B12 per day in the best case scenario. That still does not seem to be enough to explain such high B12 levels.

However, the semi-vegans did eat other sea vegetables and many sea vegetables are known to have B12 analogues. Generally, blood B12 levels of people who eat significant amounts of sea vegetables cannot be considered reliable, because the testing methods cannot discern between active and inactive B12 analogues.

There have been quite a few studies measuring the vitamin B12 content of nori. But only one has actually tested the seaweeds’ effect on methylmalonic acid (MMA) levels. MMA is the only marker that can determine true vitamin B12 activity as it is not impacted by high folate intakes. When there is not enough active B12 in the blood, MMA levels rise. The one study on nori that measured nori’s effects on MMA levels found that it increased MMA levels, though the increase was statistically significant for only dried nori and not from raw nori. This means that dried nori had anti-B12 activity, while the raw nori did not improve nor harm B12 status. Most nori eaten in the U.S. is dried.

This current study on semi-vegan Buddhist nuns in Korea could have at least partially solved this whole question of B12 sufficiency by testing MMA levels. Although it would not necessarily have meant that the nuns’ were getting most of their vitamin B12 from nori, healthy MMA levels would have at least indicated if most of the B12 in their blood was active.

The study that really needs to be done is to take some willing vegan participants in the Western world and have them avoid all B12 supplementation until their MMA levels increase above normal. Then feed them nori purchased in stores in the U.S. and see what it does to their MMA levels and how much is needed. If their MMA levels improve, then the same study should be performed a few different times on different people and with different batches of nori. Three successful studies like this would satisfy me that nori is a reliable source of vitamin B12 for vegans. Until these studies are done, choosing nori instead of B12-fortified foods or supplements could result in vegans harming themselves.

In countries where vitamin B12 fortification or supplements are not readily available, it makes perfect sense that researchers would hope that B12 would be in an available food such as nori. And, while I am quite skeptical of its reliability, I certainly hope nori turns out to be a reliable source of vitamin B12.

While I would be very happy to see a new source of vitamin B12 for vegans, especially in developing countries, this would not therefore prove that a vegan diet is “natural”. That question is answered by the fossil evidence as to whether Homo sapiens ate animal products throughout our evolution, and not whether plants could theoretically provide all the nutrients necessary for sustaining human life.

Humans have always had a rich, vegan source of vitamin B12 close by – our feces. Human feces contain much active vitamin B12. However, that does not mean that anything that gets contaminated with the bacteria from human feces is, therefore, also a rich source of vitamin B12. I have yet to see convincing data that human feces contamination on food, in water, or just in the soil can produce enough vitamin B12 to sustain humans, much less keep their homocysteine at a healthy level.

Reference

1. Lee Y, Krawinkel M. The nutritional status of iron, folate, and vitamin B-12 of Buddhist vegetarians. Asia Pac J Clin Nutr. 2011;20(1):42-9. Link

This entry was posted on Monday, October 3rd, 2011 at 6:12 pm and is filed under Vitamin B12. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.