Soy beans - healthy or harmful?

Soy beans were not too long ago touted as a ‘miracle food’ that can prevent cancer, the ideal substitute for meat.

Today, a number of respected health writers are advising – even warning – against the consumption of soy. They include Dr Joseph Mercola, who runs probably the most widely read health website on the Internet, as well as Sally Fallon and Dr Mary Enig from the Weston Price Foundation, which promotes traditional foods and diets.

These warnings are a bit hard for Asians to swallow, since soy products like tofu are very much part of the regular Asian diet. This article will put some of the soybean warnings in perspective and examine to what extent soy products are, indeed, harmful to health.

Soy consumption started in China and during the Zhou Dynasty (1134 to 246 BC) the soybean was regarded as one of the ‘five sacred grains’. The rest were millet, rice, barley and wheat.

Historical evidence suggests, however, that soy beans were not used as food before the Zhou dynasty. Instead, soybeans were used mainly in agriculture, as part of crop rotation. Farmers planted soy beans to enrich the soil.

During the Zhou Dynasty, fermentation of soybeans was discovered and this led to the production of foods like soy sauce, miso and douchi (Chinese fermented black beans). Tofu or bean curd came later, probably around the 2nd century BC.

The use of soy products later spread across Asia. Natto, a form of fermented soybeans popular in Japanese cuisine, is believed by some food historians to have also originated from China during the Zhou period. Tempeh, also made from fermented soybeans, originated in Indonesia.

Thus, the first soy products to be eaten were made fermented – not from regular beans.

And even when Asians ate non-fermented soy products like tofu, these were eaten as side dishes. The main food in traditional Asian diets has always been grains – such as rice, millet, barley or wheat.

And the second main food has always been vegetables. Beans, including tofu and fermented soy products, never formed the main part of typical Asian diets.

There is debate, however, about exactly how much soy products do Asians eat. Some studies indicate that the amount is very little.

For example, a 1998 study by Japanese researchers, published in the Journal of Nutrition, suggested that the average Japanese consumes only about 8 +/- 4.95 grams of soy beans and soy products per day for men, about 6.88 +/- 4.06 grams per day for women. (Nagata C, Takatsuka N, Kurisu Y, Shimizu H; J Nutr 1998, 128:209-13).

In their article warning against soy, Sally Fallon and Mary Enig cites KC Chang, editor of Food in Chinese Culture, saying that soy products made up only 1.5 percent of total calorie intake of the Chinese during the 1930s, compared with 65 percent of calories from pork.

Critics of these statistics argue, however, that the average soy consumption is not as relevant as the amount of soy products consumed by those groups of Asians known for their good health and longevity – particularly the people of Okinawa.

Okinawans are said to have the highest rate of soy consumption in the world, eating about 20 times more soy beans and soy products than the average Asian.

Even then, however, the Okinawans do not eat things like tofu steak and tofu burgers, nor do they drink a few glasses of soy milk every day, which is what some health-conscious Westerner vegetarians do.

This is food for thought. In the next article, we look at some of the scientific claims about the harm of soybeans and soy products.

Click here to read about aduki, soy beans and other bean products in the marcrobiotic diet.

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