The Chinese have recognized the health benefits of soybeans - known as "the greater bean" - for over 5,000 years. In general, Asian cultures have lower rates of heart disease, prostate and breast cancer than Americans, perhaps because of their diet.
Following this example, soy has recently become a popular meat alternative for many health-conscious Americans. "As an alternative to some of the greasy foods at the dining hall, I like to snack on soy nuts and power bars [with soy], and toss tofu on my salads. The benefits of soy in the news got me started on these," senior Katy Decelles said.
Soy is eaten by two-thirds of the world's population; over 2,000 products on the market contain soy. According to the National Soy Council, consumers spent almost $2 billion last year on soy foods such as soy sausage, "not" dogs, "sham" burgers, soy cheese, yogurt, ice cream, and tofu. There are even soy nuts and soy schnitzels! But why this craze for soy?
"Nutritionists think [soy] is the best thing since whole-grain sliced bread," said Dr. Lon White, a soy investigator at the Pacific Health Research Institute, in an interview with the Los Angeles Times.
In general, soy is a versatile food, dense with lots of nutrients. Soy is high in polyunsaturated fatty acids (PUFA), the good fat; low in saturated fat and cholesterol; full of the essential amino acids; and is a good source of B vitamins. Soy protein contains a high quality vegetable protein that has a lot of phyto (plant) chemicals, which help to reduce the risk of disease. Furthermore, tofu (soy curd) is an excellent source of calcium.
In Nov. 1999, the US Food and Drug Administration (FDA) gave soy its official seal of approval by allowing soy food manufacturers to place a health claim on their products. Any soy item that contains at least 6.25 grams of soy protein, with less than three grams of fat and one gram of saturated fat, may bear the following health claim on the product label: "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."
Soy: The Good and The Bad
Twenty years ago, research showed that the isoflavones, called phyto-estrogens, in soy actually suppressed breast tumor growth in rats. Isoflavones are very similar to the human hormone, estrogen. The similarity in these two compounds causes scientists to believe that soy may curb tumor growth by inhibiting the action of human estrogen, which contributes to the growth of cancer cells.Similarly, studies have shown that women who eat soy during their youth have a decreased risk for breast cancer later in life. Also, in examining medical records from Asia, epidemiologists found that Asian women are two-thirds less likely to develop breast cancer than are American women.
Even in light of these studies exhibiting the benefits of soy in terms of breast cancer, some conflicting experimental results surface as well. For example, a clinical study showed that women who took soy supplement pills were at a greater risk for breast cancer than were the women who took the placebo (sugar) pills.
In animal studies, researchers have found that in the presence of tumors, when the animals were fed soy isoflavones, the cancer cells reproduced. Experts warn women who have had breast cancer, or those who are high risk for the disease, not to include a large amount of soy in their diet.
More than 2,000 scientific papers were published last decade on the association between soy and cancer, but confusion remains because cancer is a complicated disease and plants, such as soy, are complex organisms. However, despite the lack of conclusive answers in this area of research, the overall consensus is that the benefits of soy far outweigh the risks.
To further confuse the consumer about soy, a study published in April 2000 showed "accelerated brain aging" and increased signs of Alzheimer's disease in men who ate tofu at least twice a week. However, this same study concluded that the men who ate tofu had a 65 percent lower incidence of prostate cancer than their anti-soy counterparts. Scientists could argue that if a causal effect existed between soy and Alzheimer's or increased brain aging, a greater incidence of Alzheimer's should exist in Japan and China, where tofu is eaten regularly. However, there is no argument.
Most scientists agree that 100 milligrams of isoflavones is the upper limit a person should eat daily. Eating 100 milligrams of this plant estrogen is fairly difficult in the average diet. A person would have to consume soy protein powder or pill supplements to reach this unofficial upper limit - but experts warn consumers to use caution when it comes to soy supplements, because there is no guarantee that the amount of isoflavones in these supplements is beneficial or safe. To get the heart healthy benefits of soy, 25 grams of soy protein is a safe amount, as stated by the Food and Drug Administration.
As soon as any positive scientific finding is released on a nutrient or food, the average health-conscious American runs to the nearest General Nutrition Center (GNC) to purchase the most potent and condensed form of that "miracle food." But nutritionists warn against eating large amounts of any one food - the way to keep healthy is a well-balanced diet full of plant-based foods like fruits, vegetables, and whole grains and combined with a physically active lifestyle. Soy, in moderation, should be a part of this complete and healthy diet.
