Yes or no to soy?

Is All Soy Unhealthy?

The answer depends on the type of soy you choose: processed soy sausages or traditional miso soup made from fermented, organic soybeans. Isolated soy protein, found in many vegetarian convenience foods like sausages, burgers, and nuggets, is one of the most processed and unhealthy foods you can eat. Fermented soy, found in soy sauce, tempeh, and miso, is less unhealthy. While fermented soy is not health food, it is significantly better than edamame, soy protein, and soy sausages.

The History of Soybeans

The history of soy as a cultivated crop began as green manure in Asia several thousand years ago. The plant was grown for its nitrogen-fixing properties and plowed into the soil to improve its structure and nutrient content. Asians did not start eating the beans until much later, primarily in fermented forms.

In the Western world, cheap soy oil began production in the early 20th century. Today, it is found in countless products, from lecithin and “vegetable fat” in many foods to printing ink, paints, and cleaning agents. One issue is that traces of the extraction solvent (hexane) used in industrial oil pressing and protein extraction may remain in the final products, according to the Cornucopia Institute.

The surplus from oil production was initially used only as animal feed, but through an isolation process described below, isolated soy protein was developed. With the help of various additives such as flavorings, preservatives, sweeteners, emulsifiers, and synthetic nutrients, the unappealing mass was also made suitable for human consumption.

The soy many of us eat today is far removed from the traditional soy dishes once consumed in Asia. In the U.S., isolated soy protein is so common in various food products that Americans actually consume more soy than the Japanese and Chinese.

How Is Isolated Soy Protein Made?

The production of isolated soy protein, found in many vegetarian meat substitutes and protein supplements, takes place in food factories where soy is first mixed with an alkaline solution to remove the fibers. The mass is then placed in an acid bath, which is subsequently neutralized with a new alkaline solution. The acid wash is done in aluminum tanks, which means aluminum can leach into the soy mass. The mass is spray-dried at high temperatures and finally hot-pressed under high pressure. The high temperature causes the proteins to denature, making them harder for the body to digest. This is why animals raised on soy require supplements of the amino acids lysine and methionine for normal growth, according to the Select Committee on GRAS Substances (SCOGS).

Phytoestrogens and Isoflavones in Soy

According to Kwok MK, Leung GM, et al. and Miniello VL, Moro GE, et al., researchers discovered in the 1960s that soybeans contain antioxidants known as isoflavones. This sparked extensive research, resulting in tens of thousands of studies on soy and isoflavones’ potential health effects. An important finding was that some soy isoflavones have estrogen-like properties. Children who consumed large amounts of soy milk were found to have high levels of phytoestrogens, which have been linked to hormonal effects like early puberty, although definitive evidence is lacking (Kwok MK, Leung GM, et al., 2012; Miniello VL, Moro GE, et al., 2003).

According to Setchell KD, Clerici C., metabolizing these estrogen-like compounds requires specific gut bacteria, which are predominantly found in Asian populations; Westerners tend to have far fewer of them (Setchell KD, Clerici C., 2010). This raises the question of whether Asians benefit more from soy than Westerners. It is also worth noting that much of the soy research uses very high doses, sometimes focusing solely on soy protein or isolated isoflavones. This variability in methods has been highlighted as a problem, prompting the U.S. National Institutes of Health (NIH) to establish new guidelines for future soy research.

Antinutrients in Soy

One issue with soy is its high content of phytic acid, which binds to minerals and forms insoluble salts called phytates. Phytic acid is present in all fiber-rich foods, particularly whole grains and legumes, but it is especially abundant in soybeans. Normally, soaking and pressure-cooking grains or legumes can remove most of it, but the phytic acid in soybeans is unusually resistant.

According to Messina M, Redmond G., another drawback of soy is that it contains thyroid-disrupting substances, goitrogens, which may impair thyroid function. The risk appears to be greatest when consuming large amounts of soy while also having iodine deficiency (Messina M, Redmond G., 2006).

Like all beans, soybeans contain antinutrients called lectins, which are more or less toxic and serve as the plant’s defense against being eaten. Raw, mature soybeans are not safe to eat, but cooking eliminates most lectins. However, small amounts remain, and Cordain, L., warns that phytohemagglutinin (PHA) and soy lectin (SBA) can cause leaky gut by passing through the intestinal wall. The lectins in peas and lentils are less harmful but still not healthy (Cordain, L.).

According to Shrivastava A et al., another compound in soy that the body may react to is saponins. These antinutrients have soap-like properties and can create tiny holes in the intestinal lining, making it overly permeable. Unfortunately, saponins are not destroyed by cooking but are reduced through fermentation and sprouting. Soybeans have the highest saponin content of all beans, particularly in isolated soy protein (Shrivastava A et al., 2006).

How to Prepare Soy Properly

We do not recommend consuming unfermented soy at all. However, if you wish to do so, the best way to prepare soybeans is by soaking them in water with lemon overnight, discarding the water, pressure-cooking the soybeans, and fermenting them if possible. This is the traditional method used in Asia. Fermentation eliminates most of the phytic acid, lectins, and saponins, while also promoting the formation of beneficial lactic acid bacteria.

Soy Products, Japan, and Okinawa

On the Japanese island of Okinawa, residents are known for their healthy lifestyle and longevity. Their traditional diet includes meat, fish, seafood, and fresh or cooked vegetables. A significant portion of their plant-based diet consists of organic soybeans prepared traditionally through sprouting and/or fermentation. Over millennia, Okinawans have consumed one or two servings of soy daily, accounting for about 12% of their total caloric intake, according to the long-term Okinawa Centenarian Study by Suzuki M et al. (2001). Their traditional diet also includes other foods such as sweet potatoes, shiitake mushrooms, bitter melon, ginger, turmeric, and seaweed, as noted by Willcox DC, et al. (2009).

For a healthy person, occasional small amounts of soy dishes made from whole, organic, and fermented soybeans—such as miso, natto, tempeh, authentic tofu (most tofu today is coagulated rather than fermented), and “real” gluten-free soy sauce—should not pose a problem. However, it is worth noting that soy, especially tofu, is now a significant source of the toxic heavy metal cadmium, according to Adams SV, et al. (2011).

Products made from isolated soy protein and hydrogenated (hardened) soy oil should be avoided entirely. Some studies also suggest that common genetically modified soy, resistant to the herbicide RoundUp, may increase disease in lab animals, according to Séralini GE et al. (2014).

Protein

For those seeking plant-based protein without the issues mentioned above, non-GMO options with minimal antinutrients are recommended. You can find some of these proteins.

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