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

Japanese Calcium Intake Call 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 Knowledge To 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.

Vitamin 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.