Getting Pregnant in Japan – Part Four: Do Japanese Mums need less Calcium?

Japanese Calcium IntakeCall me paranoid, but I’m really worried about what my wife eats these days. This is the fourth installment in a series about my personal experience of being pregnant in Japan (or perhaps I should say, of my wife being pregnant). Although I hope that some of the observations have value for gaijin of both sexes, I’m intentionally writing this series from my own perspective – a Gaijin Father / Japanese Mother. There is no topic better than pregnancy for old wives tales to prevail and it seems that the topic of food – what you can, can’t or shouldn’t eat – really takes the cake when it comes to misconceptions in not only Japan but every country in the world. Especially when it comes to something as important as the health of your (or your wife or your baby’s) body, these stories really play on your conscience. But surely there must be one single, factual answer out there? I really wish that there had been a resource out there to tell me at the beginning what was right and what was wrong. I don’t necessarily achieve that here, but hopefully I can shed some light on the contradictions you will run up against when comparing notes with your Japanese partner. (Before going ahead you might like to read the first, second and third installments of this series first.)

One of the things that has consistently surprised me is the huge difference in nutritional information found in Japanese books vs. English books. I’m a firm believer that all human beings are the same and that we all require the same fundamental building blocks of life. While recommended intake for normal (non-pregnant) people differ from person to person a little bit according to your BMI, I personally have been amazed at the sheer scale of the difference in recommendations between our two cultures. According to Wikipedia, the average height of Japanese women is about 8% smaller than in the West (US, UK, etc). There is even some research out there suggesting that Asian babies weigh 6% less than Western babies when born. But does a 6-8% difference justify a vastly reduced vitamin intake?

So for those of you who are wondering what on earth I’m talking about. Take a look at the chart below. I put together these “recommendations” from comparing about half a dozen books in each language. Almost every book of the same language had pretty similar recommendations so I’m quite confident with the figures.

Daily recommended intake of Japanese Book English (US centric) Book Difference
Calcium 900mg 1200-1500mg 50%
Iron 20mg 30mg 50%
Magnesium 300 mg 320mg 7%
Protein 65g 75-100 grams 30%
Zinc 10mg 15mg 50%
Vitamin A 0.6 mg 0.8 mg 33%
Vitamin B1 (thiamine) 0.9 mg 1.5mg 67%
Vitamin B2 (riboflavin) 1.2 mg 1.6mg 33%
Vitamin B6 1.7mg 2.2mg 30%
Vitamin B9 (Folic Acid) 0.44mg 0.4mg -10%
Vitamin C 110 mg 85mg -25%
Vitamin D 7.5 micrograms 10 micrograms 33%
Vitamin E 10 mg 10mg Same

As you can see, there is only one vitamin (vitamin E) that has a common “recommended intake.” How can this be? It turns out that most countries around the world have specified limits and guidelines set by their local health authorities for both normal intake and for pregnant women. In Japan it is the MHLW (Ministry for Health, Labour and Welfare, 厚生労働省). I didn’t learn all of the answers that I wanted reading their homepage, but I did get a little bit closer to understanding some of the differences.

I tried to focus my study on one of the bigger, easy to understand vitamins. Let’s be honest, are we ever going to know whether there was 1.2 mg or 1.6 mg of Vitamin B2 in the Okra we had for okazu with our rice tonight? But, I figure that something as in your face as Calcium must be important enough (and easy enough to measure) to make it worthwhile looking into in a bit more detail.. At the end of the day, the baby will suck its calcium needs from the maternal skeleton if it’s mother’s intake is inadequate so you don’t have to worry about the baby, but if you’re worried about osteoporosis (骨粗しょう症, kotsusoshosho) in the Mother then this is a good time to be drinking a lot of milk (and reading this article). One of the reasons why women are more prone to osteoporosis than Men is because they never really make up the calcium that they lost during pregnancy.

At the end of the day, all I really wanted to know was how many kire (servings) of Tofu should my wife be eating every day. Could it be true that Japanese women needed less calcium than Western women? Well, according to research published by the MHLW (link), the average intake of calcium for a typical Japanese female is a mere 528 mg. Unfortunately, Calcium is quite difficult for the body to absorb and depending on your intake of Vitamin D and magnesium, on average only 10-50% is absorbed by the body – leaving you with less than 250mg/day. But wait, there’s more. The average person loses another 200-300mg of Calcium every day through their urine and sweat meaning that the average Japanese person’s Calcium intake is looking about as healthy as the national budget deficit.

Bean KnowledgeTo cut to the chase, Japanese people are not taking anywhere near enough calcium. The odds are that your wife wasn’t even taking enough to supply her own needs before getting pregnant. I’m guessing that the Japanese text books write 900mg there as a target knowing that even that will be hard for the average Japanese person to meet following a standard washoku (和食, Japanese food) diet. I guess the last thing you want is your pregnant wife stressing out about her diet as well. The best first step is to encourage her to eat as much as possible – is there any such thing as too much calcium? Anything with bones is good so bite your tongue, close your eyes and pick up half a dozen shishamo next time you’re shopping at the local Jusco.

There’s no point telling you about the obvious sources of calcium (milk, cheese and yogurt) because (a) their probably written up in your English books and (b) a lot of Japanese people just don’t like eating huge quantities of dairy products. Thankfully, there are a bunch of sources out there that you might find lined up on the shelf next to that shishamo (シシャモ, Japanese long-fin smelt) you bought at Jusco. Jako goes great on a daikon (大根, radish) salad (both good sources) especially with some goma (ゴマ, sesame seeds) sprinkled on top. and if you are tempted to cook a tuna pasta, make sure you chose the bones-and-all version. Everyone knows that tofu is a good source, but you might be pleasantly surprised to find out that seaweed (Wakame, Konbu, Hijiki etc.) is also an ally.

Anko - Sea ToadVitamin D is important for absorption and some of the great Japanese mushrooms (not the magic ones) will do the trick: Shiitake, Kikurage, etc. It’s also present in a lot of fish, but unfortunately they are generally big ones (like Swordfish and Tuna) that you will want to avoid. Some of the safer options are sardine and mackerel. If you’re really adventurous then I hear that the liver of sea toad (あんこうの肝) is high in Vitamin D, too. hmmm…

The other thing you want to take together with Calcium (at a ratio of about 1:3) is Magnesium. It acts as natures glue for the Calcium when it enters your system. If you eat 玄米 (genmai, whole grain rice) at home then you probably won’t have much of a problem but otherwise there probably isn’t that much in your diet if you eat Japanese food at home. In the West the most popular source is Nuts. Soy beans are alright so try Tofu and Miso Soup. There is also magnesium in Katsuo so maybe throw a bit extra Katsuobushi in your dashi (broth) next time, too.

27 thoughts on “Getting Pregnant in Japan – Part Four: Do Japanese Mums need less Calcium?”

  1. is it just a big circle? japanese are smaller and therefore eat less, japanese eat less and are therefore smaller…

  2. Get some folic acid supplements, those are very important for a developing fetus and I found it can be difficult for a woman in Japan to get folic acid from their daily diet. For calcium, fish is great but like you said you need to stay away from the bigger fish like tuna. They sell these little dried baby sardines that look like white rice. You can buy them at any supermarket. They have a great amount of calcium and she can use them as a tasty topping!


  3. As you alluded to, whatever your reservations are about a possible lack of nutrients, don’t stress (her) out on every little thing. Japanese food is far healthier than typical Western food, and given the variety of stuff at the supermarket, and a relatively balanced diet, I doubt you’re missing much (except maybe folic acid). It’s actually pretty easy to get enough calcium with fish, eggs and dairy stuff.

    I found smoothies are great to get the last bit of vitamins. Milk base, throw in bananas, other fruit and maybe a little carrot – yum.

    Oh, and babies with gaijin blood are huge. Both my kids were over 8 lbs at birth – and I’m only 5’9″.

  4. I agree that the Japanese diet is generally much healthier than the American one so I wouldnt worry too much about measuring nutrient intakes. Japanese comsume far less processed sugar than westerners. Eating lots of sugar causes your body to send more calcium to the blood and leads to more being lost in sweat and urine. If you eat a lot of sugar you of course need to eat more calcium but the opposite also applies.

    I wouldnt depend on mushrooms for vitamin D. Seafood (esp deep sea fish) and eggs are far better sources. Eggs in fact contain a good amount of all the necessary vitamins and nutrients you need so learn how to cook some great Okonomiyaki or mix in a raw egg with rice for breakfast.

  5. There’s also good reason to doubt the USDA guidelines, though you didn’t say whether or not your books took their figures from the US Dept. of Ag. After all, they are promoting US agricultural products.

    Jared Diamond, MD, anthropologist, and all-round smart guy recommends ANY traditional diet rather than the crappy processed food found in developed countries. So if your wife’s diet is pretty traditional Japanese, I wouldn’t worry.

    But my wife and I take a multivitamin everyday just to make sure.

  6. Hi, I’m a gaijin pregnant mom but thought I’d write to offer you some more information about tofu. Up until very recently I ate it a lot thinking it’s very healthy but after doing a fair bit of research I’ve changed my opinion and cut it out of my pregnancy diet. Check this out for the less publicized side of the soy story. Do a google search typing in the words “tofu, unhealthy” and you will find a lot more. Make up your own mind of course but I thought I would put it out there.

  7. Unfortunately, as with all things medical, its a little more complicated than this (and truth be told we still don’t know as much as we would like to). But a few points to consider

    1) Calcium is actually really complicated. It’s hard to define an RDI because there is no clinical syndrome (except maybe osteoporosis to an extent, see below) or biochemical test that purely reflects low Calcium intake.
    During pregnancy, there is increased calcium absorption in the mother’s intestines to supply calcium to the fetus. Also, excessively large intake of Calcium (eg “OD’ing” on supplements) can result in raised Calcium in the blood and urine, Kidney stones, and constipation. So as with all things, sensible moderation is the key

    2) We aren’t all the same
    e.g. Asians have far higher rates of Lactose Intolerance (making dairy products inappropriate sources of Calcium in many instances)
    Different ethinicities (esp skin colour) have different rates of Vit D production
    While I’m not sure about Vit metabolism, I know drug metabolism varies between ethnicities (so its not unreasonable to assume the same for Vits)
    – Having said that, I do agree that Japanese perceptions (esp lay perceptions) of inter-ethnic differences are not usually based on hard science (eg I’ve never seen any studies that show Japanese intestines are different in length to gaijin intestines!!)

    3) Wrt osteoporsis in women, I think the main influence is the loss of oestrogen’s protective effects on bone after menopause. It is also related to (under-) activity in older life (mechanical forces assist with bone remodelling) and as you eluded to, a lack of “laying down” of Calcium in younger years. Osteoporosis is a big problem in Japan (and other countires with aging populations as well). The main point here is that its an old person’s problem (rather than pregnant women)

    4) Yes, Folate is VERY IMPORTANT. Women planning to get pregnant should be taking Folate both before (for about a month) and during (esp first trimester) pregnancy.

    Lastly if you have any worries, then SEE A DOCTOR. That’s what they’re for. Even if they’re not sure, they should be able to put you onto someone (eg Dietician) that does know. If you can’t find a Doctor, access REPUTABLE websites (ones run by government departments or well-established professional bodies, as their information is usually evidence-based)

    Hope this helps.

  8. A friend of mine (who is a nurse) was saying that in the West you are told not to eat any kind of liver (and pate etc) because it has Vitamin A which is bad for your baby. I have no idea what that means for liver of sea toad but as far as I know liver is recommended to most Japanese Mums as a great source of iron. Apparently they used to do the same in the West until about 20 years ago when they discovered the negative side effects of Vitamin A on the fetus. Scary stuff really.

  9. Yes, calcium is very important during pregnancy, but it’s not the only thing and it all starts to get rather complicated….

    As a few people mentioned folic acid is vital and so is zinc and iron.

    A number of years ago, I had a Japanese student come to me looking terrible. I was worried if I breathed on her she’d fall over she was so thin, and she was as pale as a ghost. She told me that she was pregnant and her doctor had told her she was highly anemic. Horrified I asked if they had put her on iron suppliments, she said they hadn’t, but she’d been told to drink more milk.

    What the!!!

    While calcium is important, it’s consumption should be isolated to different times of the day and iron-rich food should be eaten at others. Calcium inhibits the absorbtion of iron. Sadly, a few weeks later, she lost the baby.

    Having said all that, I believe that some gentle suggestions are good while a woman is pregnant, but not stressing her out is also very important.

    Good luck with it all and I’m sure you’ll have a beautiful, healthy baby before you know it.

  10. While it’s not exactly the same theme as you’re refering to Melanie, there are definately some interesting things being recommended by Japanese Doctors at the moment. Apparently it is a “trend” to have a small baby these days. They say “give birth to a small baby and it will grow up to be a big one”. Whereas most cultures talk about putting on anywhere between 10-20kg during pregnancy (and not feeling guilty), you are actively made to feel guilty in Japan if you breach 10kg. Apparently the rationalization is that the smaller the baby, the easier it is to go through the birth canal. If it is easy to go through the birth canal then there will be less stress on the baby during birth and so it will be more genki. To top it all off there seems to be some stigma attached to large baby. Anything over about 3,500g is referred to as a kyodaiji (giant baby) and is deemed to be bad (generally the assumption is that the baby will have a high risk of mental problems).
    I’m not sure where the rationalization comes for that one but it just seemed like another way of adding to the stress of a first time Mother. It’s hard to please your Doctor with such high standards. Just remind your wife that whatever she does, how ever big the baby is, she’ll be alright and the baby will be alright. It’s hard to mess up a baby – evolution has made sure of that.

  11. its amazing that any of us are here today! if our mothers or grandmothers didn’t have all this infomation and vitamin RDIs and supplements how o gods earth did any of us survive?! eat “healthy”, have a “balanced diet” and cut down on the boxing…
    from Gaijin dad to be

  12. I know this post is old but..
    I am a gaijin Mum, husband is Japanese
    we have a very healthy toddler
    I ate only Japanese diet during pregnancy, for several reasons
    Me and my siblings are always sick and prone to colds etc
    My husband and his 4 siblings are always healthy
    Yes his Mum had 5 kids! She only ate Japanese food and when I was pregnant stipulated I did too, crunchy little fish, tofu, natto, miso soup with the wakame in it, She said the wakame helps to bring in the milk too for breastfeeding
    It also cleanses your body of toxins to eat some type of seaweed everyday (thats why the people who ate such a diet after the Nagasaki bombings didnt get as sick as mainland people)
    Although there are studies showing negative results from soy, I just think that Japanese and indeed Chinese have a much longer history than ours and a much longer life expentancy also…..

    The most important thing is to have a balance and also remember your rainbow of colours in your diet, purple, orange, red, yellow, green etc,,,,

  13. Just get your wife to take a pregnancy vitamin supplement, like Blackmores Breastfeeding and Pregnancy Multivitamin.

  14. I wouldn’t be too worried about most of those vitamins as we’re looking at less than several milligrams of difference in most of them. As mentioned above, a multi-vitamin sounds like a good idea, and Japan has more multi-vitamin gel drinks that I know what to do with.

    I think you touched on a good point, though — the calcium difference, even percentage-wise, is troubling. I would agree that Japanese people as a whole do not get enough calcium, and it is very commonly said that there is no such thing as too much calcium. In the end, my opinion is that no one deserves to become bent at 90 degree angles like a significant portion of the Japanese elderly.

  15. You might also want to check out this note from the US Embassy in Japan:

    What About Having a Baby in Japan?

    One resource you may wish to look into is “From Pregnancy to Childcare: How to Prepare for Childcare in Japan,” available as a video (Y3000; 30 minutes, available in Japanese, English, Spanish, Portuguese, Chinese, Korean, Thai and Vietnamese) or in text form (Y1500; English, Spanish, Portuguese, Chinese, Korean, Thai and Vietnamese versions available, 50 pages including Japanese translation) from the AMDA International Medical Information Center.

    See for more details, or call AMDA International Medical Information Center Tokyo at 03-5285-8086 or AMDA International Medical Information Center Kansai at 06-4395-0555.

  16. im a gaijin mom also during my pregnancy in my 3kids i eat nato rice..during snack time.its best !4 pregnancy diet.

  17. URM. whilst ur post is good in the sense u talk about which foods contain loads of calcium.. You seem to imply that japanese ppl and japanese babies are smaller sized than caucasians due to their diet. Like duh.. what abt genetics…????!!!

  18. I am pregnant also. And I’m Gaijin live in Japan.

    I feel bad to be careful about my nutrition & weight. From Japanese Book said I have to control weight up only 8-10 Kgs until delivery.
    While other countries allow up 12-15 Kgs.

    And my HB’s mother wants me to use OBI wrap around my Tummy for controlling baby’s size!!

    What I should do??

  19. Patch,
    Actually I’ve been doing quite a bit of research into the whole weight gain issue and was thinking about writing a follow up article in this series about it – you’ve motivated me to get pen to paper. In short ignore what the Japanese books say and I will hopefully have some concrete evidence to arm you with for next time you speak with your hubby’s mother. I don’t know much about the OBI issue yet so if any other readers can comment that would be great.

  20. Thanks RED,

    I will try my best to keep healthy… I care only my & my baby health.
    I won’t wrap my tummy for sure…that’s weird.
    Anyway, I found that issue in a new mother book also.
    (Hajimete no Ninshin to shyussan of Saitoushya company)

    (^_^) Tc

  21. Thank you for this useful information.
    I want to ask if anyone is taking spirulina. I have been taking spirulina for couple of months, and I find it doing well to my body. Now I’m trying to get pregnant and starting to take pre-pregnancy pills too (Elevit)
    I don’t know if it is safe to continue to take both spirulina and Elevit together.
    Thanks in advance for any comments and advise.

  22. Also different nutrients are absorbed differently, depending on the source. I’ve heard that calcium is not absorbed as easily from dairy products as from other sources. In general, japanese seem to do well even with different nutritional guidelines so if your wife eats a good variety of foods and traditional japanese, she’s most likely all good.

    We do not know all about nutrition, so concentrating on specific amounts of specific stuff is most likely to get thrown off the good nutritional track.

    Oh, and about vitamin d: that’s probably ok with the japanse fish-based nutrition, and simply stay 10 minutes in the sunlight daily during summer….that’s enough to load day’s intake and more.

  23. I found some of what you wrote informative.

    I am not interested in reading baby books as what info I’ve gotten is from the net and the watching other people.

    About nutrition, well, I was all over my Japanese wife about this from day one and got her on folic acid and an excellent organic multi. I am not a harsh person but the baby will be mine too and my wife (thank god!) is a real team player. She can speak fluent English which also helps when we talk baby stuff.

    Baby is 27 weeks.

    Good luck to me 😉

    Good website.

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