Tofu and Soy Beans

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).

Protein

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) adsorbed 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.[4] 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."[5]

Isoflavones

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. [7]. Nevertheless, this is a single study and by itself, does not show conclusively that soy isoflavones causes 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."

A possible reason behind the correlation between brain atrophy and tofu consumption in L.R. White's study is that the individual subjects in the study have consumed tofu from the same source, a local tofu manufacturer in Hawaii that processed the tofu in heated aluminum containers. The aluminum that was released from the containers may have been a significant contributing factor to the brain atrophy of these individuals.

Choosing Tofu

Unless one purchases it in sterilized containers, tofu does require some choosing when purchasing and some care while storing:

Tofu can easily be spoiled if not refrigerated properly during transportation; any trace of sour odour or taste is a tell-tale sign of staleness or spoilage.
Smaller supermarkets may sell sour tofu because some do not use refrigerated trucks for delivery.

Once purchased, unpackaged tofu should be kept in the refrigerator. The water in which the tofu is kept should be changed on a daily basis and the tofu should be consumed or cooked within several days. Tofu in sealed packages can be kept from one to several weeks in the refrigerator. Tofu packaged in aseptic Tetra Brik containers have a shelf life of one year if unopened.

Information courtesy of Wikipedia