WHAT IS TOFU?
Tofu (the Japanese Romaji spelling), also called doufu (the Chinese Pinyin spelling often used in Chinese recipes) or bean curd (the literal translation), is a food of Chinese origin, made by coagulating soy milk, and then pressing the resulting curds into blocks. The making of tofu from soy milk is similar to the technique of making cheese from milk. Wheat gluten, or seitan, in its steamed and fried forms, is often mistakenly called "tofu" in Asian or vegetarian dishes.
Tofu is made by coagulating soy milk and pressing the resulting curds. Although pre-made soy milk may be used, most tofu producers begin by making their own soy milk, which is produced by soaking, grinding, boiling, and straining dried (or, less commonly, fresh) soybeans.
Coagulation of the protein and oil (emulsion) suspended in the boiled soy milk is the most important step in the production of tofu. This process is accomplished with the aid of coagulants. Two types of coagulants (salts and acids) are used commercially. The third type of coagulant, enzymes, is not yet used commercially but shows potential for producing both firm and "silken" tofu.
NUTRITION AND HEALTH INFORMATION
Tofu is low in calories, contains beneficial amounts of iron (especially important for women of child bearing age) and has no cholesterol (a risk factor for heart disease). Depending on the coagulant used in manufacturing, the tofu may also be high in calcium (important for bone development and maintenance), and magnesium (especially important for athletes).
Tofu is relatively high in protein, about 10.7% for firm tofu and 5.3% for soft "silken" tofu with about 2% and 1% fat respectively as a percentage of weight.
In 1995, the New England Journal of Medicine (Vol. 333, No. 5) published a report from the University of Kentucky entitled, "Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids." It was financed by the PTI division of DuPont, The Solae Co. St. Louis, Missouri. This meta-analysis concluded that soy protein is correlated with significant decreases in serum cholesterol, Low Density Lipoprotein LDL (bad cholesterol) and triglyceride concentrations. However, High Density Lipoprotein HDL (good cholesterol) did not increase. Soy phytoestrogens (isoflavones: genistein and daidzein) absorbed onto the soy protein were suggested as the agent reducing serum cholesterol levels. On the basis of this research PTI, in 1998, filed a petition with Food and Drug Administration for a health claim that soy protein may reduce cholesterol and the risk of heart disease.
The FDA granted this health claim for soy: "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease." One serving, (1 cup or 240 mL) of soy milk, for instance, contains 6 or 7 grams of soy protein.
In January 2006 an American Heart Association review (in the journal Circulation) of a decade-long study of soy protein benefits cast doubt on the FDA allowed "Heart Healthy" claim for soy protein. Among the conclusions the authors state, "In contrast, soy products such as tofu, soy butter, soy nuts, or some soy burgers should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health."
Soy isoflavones have not been shown to reduce post menopause hot flashes in women and the efficacy and safety of isoflavones to help prevent cancers of the breast, uterus or prostate is in question. Thus, soy isoflavone supplements in food or pills is not recommended. The original paper is in the journal Circulation: January 17, 2006.
A study done by the Pacific Health Research Institute followed over 3000 Japanese men between 1965 and 1999, which showed a positive correlation between brain atrophy and consumption of tofu. Nevertheless, this is a single study and by itself, does not show conclusively that soy isoflavones cause brain atrophy.
This study by L.R. White, et al., from the National Institute of Aging, NIH, was rejected as not credible by the Food and Drug Administration when it issued its health claim for soy: "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease."