My vegetarian friends, especially, aren't going to like this post, but the amount of soy in processed foods means that most Americans, vegetarian or not, eat a lot of soy. Soybean oil is extensively used, while textured vegetable protein (TVP), soy flour, and soy protein isolates can be found in all kinds of packaged foods.
But soy is just not meant for human consumption--unless it has been fermented (and tofu is not really in this category).
Wait, wait! you say. Hasn't it been found to be helpful in preventing heart disease? And aren't there other health claims made for it? And isn't it a great meat substitute, since it contains all the amino acids, which most legumes do not?
Yes, that's what we've been told, and have we ever. Thanks to a massive advertising campaign on the part of the soy industry, as well as to the FDA's 1999 allowing of claims linking soy consumption to a healthier heart, the years from 2000 to 2007 saw over 2700 new soy-containing foods appear on supermarket shelves (sorry, no link; registration and download required).
So what's wrong with soy? Let me count the ways ...
First, the very substances that have been touted as beneficial turn out to be harmful: the isoflavones, also called phytoestrogens.
Isoflavones are goitrogenic: they depress the functioning of the thyroid. Less than two glasses of soy milk, two servings of tofu, or a handful of roasted soy nuts per day can depress thyroid function in women. If you're eating soy meat-replacement products and drinking soy milk regularly, you may be at risk for depressing thyroid function.
Depressed thyroid function has a whole host of nasty consequences, including, in severe cases, mimicking Alzheimer's disease. It can also cause heart problems--the very thing that isoflavones are said to prevent. In fact,
no study has ever offered direct proof that soy can prevent heart disease and in most of the major studies in which cholesterol levels were lowered through either diet or drugs, a greater number of deaths occurred in the treatment groups than in controls, deaths from stroke, cancer, intestinal disorders, accidents and suicide.
Because phytoestrogens act like estrogen on the body, some researchers suggest that soy-based infant formula may account for the alarming growth in premature physical maturation of girls and deficient male hormone in boys.
There are other harmful substances in soy. One is phytic acid, which blocks the absorption of zinc, which is essential for mental functioning. Soy also blocks absorption of calcium and vitamin D, necessary for good bone health. Yet some soy proponents claim that soy helps prevent osteoporosis!
Enzyme inhibitors present in soy interfere with digestion and block the breakdown of protein. This probably accounts for the digestive problems and allergic reactions many people have to soy products.
Soy also contains hemagglutinin, which causes red blood cells to clump together and can cause blood clots. I wish I'd known this back when I was eating soy--I have suffered from blood clots, and it would have been prudent to avoid soy products.
All these and more occur naturally in soybeans. I haven't even talked about the processing of soy into its various forms, from oil to TVP. These processes are meant to get the toxins out of soy, but they're not fully successful. And the processes themselves have some nefarious effects: depending on the end product, aluminum is leached into the final product; high-temperature processing denatures the protein in the soy, so that, for example, lysine has to be added to soy-based cattle feed; nitrites, which are carcinogens, are produced. With soybean oil, hexane is used as a solvent, and some remains in the finished product. High temperatures and other steps in the process form free radicals, which, as we all know by now, are carcinogenic.
But haven't Asians eaten soybeans for thousands of years? Yes and no. Sally Fallon and Mary Enig write:
During the Chou Dynasty (1134 - 246 BC) the soybean was designated one of the five sacred grains, along with barley, wheat, millet and rice. However, the pictograph for the soybean, which dates from earlier times, indicates that it was not first used as a food; for whereas the pictographs for the other four grains show the seed and stem structure of the plant, the pictograph for the soybean emphasizes the root structure. Agricultural literature of the period speaks frequently of the soybean and its use in crop rotation. Apparently the soy plant was initially used as a method of fixing nitrogen.3 soybean did not serve as a food until the discovery of fermentation techniques, sometime during the Chou Dynasty. Thus the first soy foods were fermented products like tempeh, natto, miso and shoyu (soy or tamari sauce). At a later date, possibly in the 2nd century B.C., Chinese scientists discovered that a puree of cooked soybeans could be precipitated with calcium sulfate or magnesium sulfate (plaster of Paris or Epsom salts) to make a smooth pale curd - tofu or bean curd. . . . The increased reliance on bean curd as a source of protein, which occurred between 700 A.D. and the present time, has not necessarily been a beneficial change for the populations of the Orient and Southeast Asia.
Fermented soybeans don't contain the toxins and other harmful components of raw or cooked beans. And it should be remembered that the typical Chinese or Japanese diet utilizes fermented soybeans, as well as tofu, as condiments and flavorings, for the most part. When tofu is consumed along with meat or fish, the mineral-blocking properties of soy are reduced, and that is how it is generally consumed in Asia.
Don't take my word for any of this: look into it for yourself. I have never made a secret of the fact that I view the food industry with wariness and distrust, so I'll admit to having a very strong bias against industry claims. The food industry is driven by one thing and one thing only: profits. Here are some links--including to a couple of pro-soy articles--to check out (including the ones in this post); they contain numerous references to scientific studies:
What About Soy? (pro-soy)
A Sensible Part of Your Diet (pro-soy)