Vitamin B12 in Pregnancy, Miso, and Tempeh

B12 and Neural Tube Defects

An NIH news release today shows that low levels of vitamin B12 in pregnant women may increase the risk of neural tube defects. The authors conclude their paper by saying, “Our [analysis] suggests that women who start pregnancy with serum vitamin B12 concentrations below 300 [pg/ml] (221 pmol/L) are at significantly higher risk for [neural tube defects]. Improving B12 status beyond 300 [pg/ml] might offer further risk reduction but this is unclear.”

In my epic novel, Vitamin B12: Are You Getting It?, I recommend that all vegans keep their vitamin B12 levels at 350 pg/ml or higher (click here for that info, scroll to bottom of page). In order to do this, vegans should follow these recommendations.

And on this page, B12 and Chronic Disease: Homocysteine, I warn that low B12 levels could cause neural tube defects.

So, none of this is terribly new or surprising. And while the NIH news release did not mention vegans, it didn’t stop The Telegraph from writing headlines that make it sound like the study was performed on vegans and showed vegans to have higher rates of neural tube defects:

Vegan diet increases the risk of birth defects, scientists warn
“Women who are strict vegetarians or vegans may be a greater risk of having a child with birth defects because they are likely to be deficient in vitamin B12, researchers warned.”

The study confirms that it is important for vegan women who want to get pregnant to make sure they are following vitamin B12 recommendations. Luckily, I rarely come across a pregnant vegan who does not know the importance of making sure she is getting vitamin B12.

Tempeh & Miso

In somewhat related news, I picked up a professional-looking flyer promoting veganism the other day at a local vegetarian restaurant only to read in it that miso and tempeh have vitamin B12. On the bright side, at least they mentioned vitamin B12 and suggested supplements and fortified foods. However, the mold required to produce tempeh does not produce vitamin B12, so the only way B12 would be in tempeh is if it was contaminated with B12-producing bacteria, and in most cases it won’t be. Two studies have measured the vitamin B12 content of miso and have found none. More information can be found in B12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods.

10 Responses to “Vitamin B12 in Pregnancy, Miso, and Tempeh”

  1. Elaine Vigneault Says:

    Going out to eat at restaurants that aren’t specifically vegan restaurants you’re bound to get animal products every now and then. I ate Thai for a long time without realizing many Thai chefs use fish sauce in most dishes. Then there are the accidents – where I ordered the pasta without shrimp but it came with shrimp anyway and I didn’t realize until after the first couple bites or where I ordered ithe salad without cheese and it came with cheese, but in a rush I just pushed it aside instead of sending it back to the kitchen.

    Mistakes happen. Trying to find the silver lining in what seems to be a purely gray cloud, I rationalized that maybe this is one way that vegans who don’t supplement with B12 might get their B12… without even trying 🙂
    Something to consider.

  2. Jack Norris RD Says:

    When I first went vegan back in the late 80s, I thought the same thing based on the ideas that animal groups were promoting at the time; specifically that the body only needs minuscule amounts of B12 and that it stays in the body for many years. But, while the body doesn’t need large amounts of B12 compared to most other vitamins, I’m afraid it needs a lot more than can be provided in accidentally consuming non-vegan foods.

  3. Nina Planck Would Be Proud | Says:

    […] He has no excuse to be this incompetent and misinformed. I’ve linked to this before but here is Jack Norris’ take on the […]

  4. Hugo Pottisch Says:

    Me does not like the B12 is in seaweed, miso etc flyers either. Insects are rich in B12. Apes are virtually vegan except for the insect part. These days we wash off everything that might carry B12 producing bacteria or the vitamin itself.

    I had a similar experience to Jack. When I first went vegan – I did not know about B12. Heck I did not even know the term “vegetarian” let alone “vegan”. Back then you were still arguing over how to get protein. When I first heard about the B12 issue – I got myself tested. I had been vegan for less then five years at the time, 3-4 I think, and the results were fine. However – I started supplementing and have done so ever since.

    In the meantime I have met vegans who had good B12 levels even after 5 years without supplements. I have also met some who had low levels after only 1-2 years. Then, later, I discovered articles such as this one on the USDA web site:

    B12 Deficiency May Be More Widespread Than Thought

    Interesting quotes are:

    Nearly two-fifths of the U.S. population may be flirting with marginal vitamin B12 status if the population of Framingham, Mass., is any indication.

    Oddly, the researchers found no association between plasma B12 levels and meat, poultry, and fish intake, even though these foods supply the bulk of B12 in the diet. “It’s not because people aren’t eating enough meat,” Tucker said. “The vitamin isn’t getting absorbed.”

    “The good news,” said ARS administrator Floyd Horn, “is that most people can improve their B12 status by eating more fortified cereals and dairy products. Dr. Tucker’s findings show that these foods were nearly as effective as supplements containing B12 for getting people’s blood levels above the danger zone.”

    My guess is that B12 aware vegans have hence the lowest risk of deficiency. We should warn our meat-eating and B12 ignorant friends that they are at risk and that animals cannot necessarily save them.

    Just like the omega 3 hype by the seafood lobby – the meat lobby is doing a lot of damage with their “only vegans are at risk of B12 deficiency” reporting. I don’t mind personally because, as Jack, I can sit back, relax. We know that our B12 levels are good. But there are meat-eating pregnant women out there who think that they should be fine too and they might not be.

  5. Jack Norris RD Says:


    I think you make an excellent point – that vegans who are aware of the need for B12 are probably less likely than meat-eaters to suffer from B12 deficiency (especially mild B12 deficiency). I do know of many vegans, and many others are reported in the scientific literature, who have come down with very serious B12 deficiency because they did not supplement and their body ran out of their previous stores.

    > Insects are rich in B12.

    I think this is a possibility, but when I looked at the research I actually was surprised at how little B12 was in the insects that had been measured.

    > These days we wash off everything that might carry B12 producing bacteria or the vitamin itself.

    I have also not seen any good evidence of B12 occurring in soil or water in any measurable amounts. It does, however, occur in feces in large amounts.

  6. Hugo Pottisch Says:

    Apes eat mostly termites. It is interesting to note that most scientific research that I could find indicates that termites are rich in B12. E.g. USDA scientists on: Vitamin B12 levels in selected insects

    Here an the abstract:

    Vitamin B12 concentrations were determined by radioassay in the housefly, five species of termites, and 17 other phylogenetically diverse insect species. Vitamin B12 was not detected in the housefly Musca domestica, which apparently cannot interconvert propionate and succinate. In contrast, the termite Zootermopsis angusticollis readily interconverts succinate and methylmalonate, and contains high amounts of vitamin B12 (940 pg/mg dry tissue), as do four other species of termites. Experiments involving selective elimination of either gut tract protozoa or bacteria in Coptotermes formosanus indicate that intestinal bacteria are the major source of vitamin B12 in this termite. The other insect species examined have undetectable to moderate amounts of vitamin B12.

    I would not be surprised if ants had B12 as well… And here we go with our washing and making sure we kill and remove all B12 sources that voluntarily enrich our foods in the kitchen 😉

  7. Kostas Says:

    About Vitamin B12 Recommendations in pregnancy. Is it safe the dosage of 1000μg two times a week?

    Are there any official recommendations or studies about supplements of B12 in pregnancy?

    1000μg sounds too much for pregnancy (two dosages/week). Are there any studies to confirm the safety? Are the frequent smaller dosages safer for pregnancy than the 1000μg or it does not matter due to the smaller absorption?

    For a pregnant vegetarian (not vegan) woman, that starts pregnancy with levels below 350, which should be the initial dosage and for how long (in your book you suggest 2 weeks daily for someone that has not frequent dosage).

    Thank you for your time!

  8. Jack Norris RD Says:


    > For a pregnant vegetarian (not vegan) woman, that starts pregnancy with levels below 350, which should be the initial dosage and for how long (in your book you suggest 2 weeks daily for someone that has not frequent dosage).

    I don’t know how far below 350 her levels are. But if she’s vegetarian, rather than vegan, without knowing her exact levels I’d say that she doesn’t need the two weeks of daily 2,000 µg doses.

    > 1000μg sounds too much for pregnancy (two dosages/week). Are there any studies to confirm the safety?

    I’m not aware of any studies but based on typical absorption rates, it shouldn’t be a problem.

  9. Kostas Says:

    Thank you Jack for your time,

    295 are the levels, the doctor suggested a prenatal supplement with 2.5μg and she consumes daily 3 dairy (1μg B12 each). Should the recommendations for 2000μg cyanocovalamin per week be followed despite the fact that she eats dairy and consumes 2.5μg B12 from the prenatal?

    Your book, is the only one that has specific recommendations for all the nutrients and for all life stages. Great Work!

    Thank you again!

  10. Jack Norris RD Says:


    There should be no need for her to supplement with 2,000 µg per week.

Leave a Reply