Sally Fallon is one of the most outspoken anti-soy personalities. One of her recent articles begins: “The propaganda that has created the soy sales miracle is all the more remarkable because, only a few decades ago [sic], the soybean was considered unfit to eat – even in Asia.” I assume “decades” should be replaced with centuries or millennia because it is an ancient plant. And, as befits an ancient plant, there are many, many different stories about its history. One says that Samuel Bowen brought the soybean to the US in 1765 and exported soy sauce and soy noodles to England. Large-scale production of soy in this country began around 1850.
The history of soy in China and its spread through Asia date much further back in time. According to the James Beard website, soybeans have been cultivated in China since 1000 B.C. and soy sauce as we know it did not come about until the 6th century. Prior to that time, soy sauce apparently was a runny, whole bean sauce used as a preservative. Another source tacks on almost 2000 more years, reporting that first written record of soybean cultivation is from China in 2838 B.C. In contrast to Fallon, this source claims that Chinese farmers fed soy to their families as well as to their livestock rather than simply using it as a nitrogen-fixing crop. As botanical, archaeological, and linguistic research are integrated, it appears that the domestication of soy by trial-and-error began around 1600 BC and it was a successful agricultural crop by the eleventh century B.C.
Ultimately, the plant has such a long history with man that it no longer grows in the wild. In my opinion, a long history of use of a plant by man, especially as a food, provides significant evidence of safety and compatibility. I think it is something worth remembering as we go through these anti-soy positions.
The Fallon article claims that it took a long time for soy to become a food because it contains potent enzyme inhibitors that block enzymes needed for protein digestion. “They can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer.”
Soy certainly does contain trypsin inhibitors that are reduced by heat and fermentation but not entirely removed. They can act as anti-nutrients but also may provide an anti-cancer benefit. As one review concludes: “Whether there are adverse or beneficial effects of residual inhibitors in food is not known.”
But what about the risk of pancreatic cancer Fallon mentions? That comment is based on rodent studies. Rodents developed pancreatic issues when fed a diet of raw soybean flour. Of course, when we discuss soy in the human diet, we are not talking about people habitually eating raw, uncooked, ground soybeans. Moreover, raw soybean flour fed to monkeys for 4 years and baboons for 4 months (yes, a ridiculous, pathetic use of primates in research given that we have tens of millions if not billions of people voluntarily eating soy to study) developed no pancreatic problems. And no epidemiological data has surfaced suggesting that residual trypsin inhibitors are an issue in humans, let alone something as serious as a likely cause pancreatic cancer.
The biggest problem with soy is that it is a huge crop and is butting heads with some other big food giants: Dairy and meat. There are thousands and thousands of studies of varying quality and with varying indications of bias on both sides of this fence. I cannot provide the definitive word on the anti-trypsin effect of soy foods but I do have two studies that I believe should have the last word on the question of the dangers of soy trypsin inhibitors: The first reports that in areas of Japan where more soybean products are consumed, the incidence of cancer is low, a factor attributed to the anti-trypsin effects of soy. The people in the Okinawa Prefecture eat almost 83 grams (about 3 ounces) of soy a day, and eat trypsin inhibitors daily. The study noted that the local people have been ingesting a measurable amount of active trypsin inhibitor “for many years without adverse effects.” The second is a large dietary study on colorectal cancer. In this prefecture, eating patterns settled in to three types. One of those, “the prudent diet” came with a reduced risk of colon cancer. This diet contains large amounts of fruits and vegetables, soy, and seafood.
I am not a soy advocate and I think it is fine to live a life without soy. At the same time, I am absolutely not impressed by the anti-soy movements arguments. There is much evidence that traditional soy foods (as opposed to soy lecithin and soy protein isolate) can be a very good component of a healthy diet and, as part of a healthy, whole foods diet, soy trypsin inhibitors are not something to worry about. Especially because soy is not the only food with trypsin inhibitors. They are common in seeds and legumes. Spinach, broccoli, cucumbers, Brussels sprouts and radishes, potatoes, and corn also have them.
Next, I will be looking into the purported dangers of soy’s phytoestrogens.
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