Soy in Okinawa: Separating Myth from Fact

How much soy do Okinawans really eat?

The “average” consumption of soy foods in Asia is not as high as many people think so soy proponents have been trying their best to turn our attention instead to soy consumption in Okinawa, an island with some of the healthiest seniors and most numerous centenarians in the world.

One of the first was vegan John Robbins, author of Diet for a New America, Healthy at 100 and other books, who suggested in an April 2004 letter to Mothering magazine that the levels of soy consumption throughout Asia are largely irrelevant, and we really need to look at the level of soy consumption “in those parts of Asia which demonstrate the highest levels of human health.”   Robbins then asserted that that “there is no question about where that is” and pointed to Okinawa as having “the best health and greatest longevity on the planet.”

Why might that be?   Robbins’ view is the Okinawans live better longer because they eat two servings of soy foods per day, with soy constituting 12 percent of their calories.  He bases these figures on the Okinawa Centenarian Study, as reported in the best-selling books The Okinawa Program and The Okinawa Diet Plan by Bradley Willcox, D. Craig Willcox and Makoto Suzuki.   To this day people repeat these figures like gospel in books, articles, blogs, YouTubes and Facebook postings.

How much soy Okinawans eat, however, is not at all clear in these two books. The authors say that the Okinawans eat “60 to 120 grams per day of soy protein,” which means, according to the books’ context, soy foods eaten as a whole food protein source. But the authors also include a table that lists total legume consumption (including soy) in the amounts of about 75 grams per day for the years 1949 and 1993. On yet another page, we learn that people eat an average of three ounces of soy products per day, mostly tofu and miso. And then we read that the Okinawans eat two servings of soy, but each serving is only one ounce.  As for soy making up 12 percent of the Okinawan diet, Robbins pulled that figure from a pie chart in which the 12 percent piece represents flavonoid-rich foods, not soy alone. Will the correct figures please stand up?

There are other credibility problems with the Okinawa Centenarian Study, at least as interpreted in the author’s popular books.  In 2001, Dr. Suzuki reported in the Asia Pacific Journal of Clinical Nutrition that “monounsaturates” were the principal fatty acids in the Okinawan diet.  In the popular books, this was translated into a recommendation for canola oil, a genetically modified version of rapeseed oil developed in Canada that could not possibly have become a staple of anyone’s diet before the 1980s. According to gerontologist Kazuhiko Taira, the most common cooking fat used traditionally in Okanawa is a very different monounsaturated fat-lard.  Although often called a “saturated fat,” lard is 50 percent monounsaturated fat (including small amounts of health-producing antimicrobial palmitoleic acid), 40 percent saturated fat and 10 percent polyunsaturated. Taira also reports that healthy and vigorous Okinawans eat 100 grams  each of pork and fish each day. Thus, the diet of the long-lived Okinawans is actually very different from the kind of soy-rich vegan diet that Robbins recommends.

Finally, the longevity of Okinawans has been attributed to many factors besides soy consumption. Indeed the three authors of the Okinawa Centenarian Study name caloric restriction as “the key to eating the Okinawa way.” And although they share the good news that diet, not genes, is the key to longevity — meaning we too can live long and well if we follow their plans — Dr. Suzuki has reported elsewhere that the genes of Okinawan centenarians actually do differ from those of normal individuals and are a factor in their superior longevity.

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This blog is excerpted from my book The Whole Soy Story: The Dark Side of America’s Favorite Health Food, which discusses soy consumption worldwide and its implications for health and longevity.

ENDNOTES

1.  Suzuki M, Wilcox BJ, Wilcox CD. Implications from and for food cultures for cardiovascular disease and longevity. Asia Pac J Clin Nutr, 2001,10,2, 165-171.

2. Taira, Kazuhiko. In Franklyn, Deborah. Take a Lesson from the People of Okinawa, Heath, September 1996, 57-63.

3. Akisaka M, Suzuki M. Okinawa Longevity Study. Molecular Genetic Analysis of HLSA Genes in the Very Old. Nippon Ronen Igakkai Zasshi, 1998, 35, 4, 294-298.