Soy Health: Tofu and Isoflavones

Image Gallery Soybeans arrived in the United States in the 1880s and quickly became a major U.S. crop. Today, the United States grows 49 percent of the world’s soybean crop. Photo courtesy of ADM

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Remember Johnny Carson? Back in the 1970s and ‘80s, when “He-e-e-e-re’s Johnny” reigned as king of late-night television, he often poked fun at health foods, in particular, tofu. Such comments resonated with meat-and-potatoes Americans, who loved to hate the bland, spongy, soy blocks.

Carson’s successor, Jay Leno, doesn’t put down tofu. During the 1990s, the nation’s relationship to soy foods changed dramatically. Tofu hasn’t exactly replaced burgers and pizza as the nation’s favorite foods, but the jokes have largely ceased. Tofu and other soy foods have become as mainstream as McDonald’s—only they’re lower in fat, much more nutritious, and appeal to a growing number of Americans committed to eating a healthier, more plant-based diet.

Today, more than 300 companies produce soy foods, according to the U.S. SoyFoods Directory. In fact, so many soy products now line the shelves and refrigerated cases of health-food stores and supermarkets that it probably won’t be long before someone opens a store that stocks only soy foods.

The bean grown round the world

Soybeans (Glycine max) were first cultivated in China as early as 2800 b.c., serving as a key source of protein for a culture that was largely vegetarian. The Chinese developed tofu around 200 b.c.

The ancient Japanese adopted soybeans and tofu. During the eighteenth century, soybeans were introduced into Europe, but they didn’t arrive in the United States until Chinese immigrants introduced the bean in the 1880s. Soybeans quickly became a major U.S. crop, raised almost entirely as cattle feed and for export to Asia. Today, the United States grows 49 percent of the world’s soybean crop.

Until the late 1960s, tofu was a curiosity in the United States, served only at Asian restaurants and in Asian American homes. Then the counterculture generation adopted it, and tofu found its way into health-food stores. More than thirty years later, soy foods are as American as Kellogg’s, the cereal company whose Worthington Foods subsidiary sells Morningstar Farms soy franks, soy breakfast links, and soy-based Harvest Burgers.

The soy-health connection

The health benefits of soy come, in part, from a group of compounds known as isoflavones. The two most prominent isoflavones are genistein and daidzein. All soy foods contain varying amounts of isoflavones. Here’s how the various types of soy foods stack up for isoflavones:

Raw soybeans (½ cup): 34 g soy protein, 176 mg isoflavones
Roasted soybeans/soy nuts (½ cup): 30 g, 167 mg
Tempeh (4 ounces): 19 g, 61 mg
Soy protein (1 ounce): 26 g, 57 mg
Soy flour (¼ cup): 8 g, 44 mg
Tofu (4 ounces): 18 g, 38 mg
Textured soy protein (¼ cup): 18 g, 28 mg
Soy milk (8 ounces): 10 g, 20 mg

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