The Archer Daniels Midland Company one of the leading producers of soy products asks on their website, "Why do the Japanese have 1/8th the incidence of prostate cancer? And few symptoms of menopause? Is it a diet rich in soy?" With 350 factories worldwide, 23,000 employees, and $18 billion in annual net sales, this agricultural powerhouse wishes good health was as simple as eating soy. However, there is very weak scientific support for the idea that the phytoestrogens in soy products can ease the symptoms of menopause, let alone reduce the risk of prostate cancer. There are a host of reasons for Japanese good health and longevity, yet Archer Daniels is ignoring sound science to support their own goals and increase sales.
Could the differences in health between the Japanese and Americans be a result of soy consumption? Cardiovascular disease, which includes heart disease, hypertension, and stroke, is the leading cause of death in the United States. For 1999, death from heart disease in U.S. was 265.8 per 100,000 and for Japan only 120.4 per 100,000. And there is some evidence supporting the beneficial effects of soy on the heart. A 1995 study in The New England Journal of Medicine compared the data from 38 clinical trials performed over 25 years and concluded that plasma cholesterol can be reduced 9.3 percent by soy protein consumption. As a result, in 1999, the Food and Drug Administration authorized the labeling of foods containing soy protein as potentially reducing the risk of coronary heart disease (CHD). By including 25 grams or 4 daily servings of soy protein in a diet low in saturated fat and cholesterol, individuals may be able to decrease their level of LDL the bad form of cholesterol.
However, the evidence supporting soy's ability to prevent cancer and osteoporosis and to ease menopausal symptoms is inconclusive. At last year's Fourth International Symposium on the Role of Soy in Preventing and Treating Chronic Disease, findings were presented from a number of studies done on the topic, but much of the data was "frustratingly inconsistent." While it would be wonderful if something as simple as soy could prevent disease, there are in reality any number of reasons for the differences in health between Japan and the United States. Yes, Japanese women eat more soy, but they also eat more fish and less fat than American women do. The lifestyles and overall diets in Japan differ considerably from those found in Western countries, and the lower daily caloric intake and/or higher activity levels of the Japanese may well account for the differences.
While the Japanese have increased longevity and lowered incidence of cardiovascular disease, breast cancer, prostate cancer, and colon cancer, they also have higher rates of stomach and liver cancer and comparable total cancer mortality rates. Yet, Archer Daniels isn't promoting this information on its website. Perhaps they should ask, "Why do more Japanese die of stomach and liver cancer? Is it a diet rich in soy?"
Similarly, the company isn't asking, "Are the long life expectancy and low disability rate of people in Okinawa caused by consumption of the Satsamu sweet potato, which accounts for the largest part of their energy intake?" After all, Archer Daniels doesn't have a vested interest in promoting Satsamu sweet potato consumption.
In this age of instant gratification, consumers are not willing to accept the answer "we just don't know" and are eager to find simple explanations. Archer Daniels and other purveyors of quick health fixes are happy to supply them.
August 23, 2002
Thank you, Ms. Strazik, for bringing some balance to the soy issue. I graduated from the Natural Gourmet in NYC, a "health-supportive" cooking school that surprisingly has the same ideas about soy as your article. There are so many different factors to look at when comparing populations that taking one factor, such as soy, and drawing sweeping conclusions is absurd. (Although at school, one of the instructors read some information about soy being toxic to the thyroid, so eating four servings a day might do some damage.) I believe much of the info given to us at school was from Sally Fallon's research.
A food historian told us soybean plants were used mostly to fix nitrogen in the soil as crops were being rotated. Until fermentation methods were discovered, soy beans were not a staple food, but lentils and other pulses were. Soybeans contain large amounts of enzyme inhibitors and phytic acid, which block absorption of nutrients and enzymes needed for protein digestion. Fermentation greatly reduces these harmful substances. If soy is eaten in an unfermented form, like tofu or soy protein isolate, these harmful substances can also interfere with digestion. There could be a link to the high rates of stomach cancer in Japan.
Many studies on soy health effects are done using soy protein isolate (SPI), which is a substance so far from the soy that Asian populations are eating that I cannot believe these studies can be considered useful yet many health foods contain SPI.
One has to wonder about any "superfoods" being marketed the way soy is.