Oct 13 2009

Always Check Your Assumptions

One of the cornerstones of faith in the low-fat diet for a long time has been the low prevalence of heart disease among Japanese people.  Way back when Ancel Keys did his famous Seven Countries study, and picked seven countries out of a bunch more that supported his thesis, one that stuck out was Japan.  Traditional Japanese at the time ate a high-carb, fairly low-fat diet based on a ton of rice and some fish, and they didn’t have much heart disease, and they got more of it when they moved to America.  Keys jumped on this as proof that fat causes heart disease, and we’ve been repeating it ever since.  You’ve probably heard it many times, maybe even repeated it yourself: if you want to be healthy and thin, eat broiled fish and rice like the Japanese.  (The reasoning behind the Mediterranean diet is much the same.)

Well, someone decided to dig further through the information and see what really accounted for the difference.  After all, there were many more differences between the Japanese and the Western world than diet, especially back in the 1950s.  To do so, they looked at Japanese Americans, and divided them into groups based on whether they followed a Japanese or American diet, and also on whether they followed a Japanese or American lifestyle (based on things other than diet, like religion, time spent in Japan, which language they spoke the most, whether they married a Japanese person, etc.).  Hyperlipid talks about the results, but I think the graphs from the study are a little confusing, so I made a simpler one of my own.

Japanese/American Diet/Lifestyle

Japanese/American Diet/Lifestyle < 45 years old

The abbreviations are Japanese lifestyle (JL) or American lifestyle (AL) and Japanese diet (JD) or American diet (AD).  You can see the four combinations of those two factors above.  The people with the lowest rate of heart disease were the ones who followed a Japanese lifestyle and an American diet—much lower than those who followed a Japanese lifestyle and a Japanese diet.  The worst was those following an American lifestyle and a Japanese diet.  Whichever lifestyle they followed, the Japanese diet pushed their heart disease numbers up.

So after all these years of people eating rice cakes and dry white fish in an attempt to be healthy, it seems they should have been eating a burger and learning to speak Japanese!

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