Writings about the soybean date back to 3000 B.C., when the Emperor of China listed the virtues of soybean plants for regenerating the soil for future crops. His praises centered on the root of the plant, not the bean. These ancient writing suggested that the Chinese recognized the unfitness of soybeans for human consumption in their natural form. Now 5000 years later, we are once again catching on to the anti-nutritive qualities of the soybean, and realizing that the only soybean worth eating is one that has been fermented.
The key to releasing the nutrients of the soybean has been known for thousands of years
About 1000 B.C. some smart person in China discovered that a mold, when allowed to grow on soybeans, destroyed the toxins present and made the nutrients in the beans available to the body. This process became known as fermentation and led to the creation of the still popular foods tempeh, miso, and natto.
A few centuries later, a simpler process was developed to prepare soybeans for consumption. After lengthy soaking and cooking, the beans were treated with nigari, a substance found in seawater. The end product was tofu. During the Ming dynasty, fermented soy appeared in the Chinese Materia Medica as a nutritionally important food and an effective remedy for diseases.
Unfermented soybeans contain potent anti-nutrients
These anti-nutrients are the way nature protects the soybean plant so that it can live long enough to effectively reproduce. They function as the immune system of the plant, offering protection from the radiation of the sun, and from invasion by bacteria, viruses, or fungi. They make the soybean plant unappetizing to foraging animals. All plants have some anti-nutrient properties, but the soybean plant is especially rich in these chemicals. If they are not removed by extensive preparation such as fermentation or soaking, soybeans are one of the worst foods a person can eat.
Unfermented soy has been linked to digestive distress, immune system breakdown, PMS, endometriosis, reproductive problems for men and women, allergies, ADD and ADHD, higher risk of heart disease and cancer, malnutrition, and loss of libido.
Groups most at risk of experiencing negative effects from the anti-nutrient properties of soy are infants taking soy baby formula, vegetarians eating a high soy diet, and mid-life women going heavy on the soy foods thinking they will help with symptoms of menopause.
Soybeans contain high levels of phytates
All legumes contain phytate (also known as phytic acid) to some extent, but the soybean is particularly rich in this anti-nutrient. Phytate works in the gastrointestinal tract to tightly bind minerals such as zinc, copper, iron, magnesium and calcium. It has a particularly strong affinity for zinc, a mineral that supports wound healing, protein synthesis, reproductive health, nerve function, and brain development. It is believed that people living in developing countries are shorter than those in developed countries because of zinc deficiency caused by eating too many legumes. There is also evidence that mental development can be negatively impacted by a diet high in phytate.
In most legumes such as other varieties of beans, soaking is enough to break down most of the phytate content. However the soybean requires that the enzymes be released in the fermentation process to reduce its phytate content to the point where it becomes fit for consumption. This means that fermented soy foods like miso and tempeh have the lowest levels of phytate and are the best choices for anyone wishing to eat soybean products. Tofu is also a good choice, as long as care is taken to replenish loss nutrients.
Whole soybeans, soy milk, soy chips, soy protein isolates, soy flour and all the other myriad of products made from processed soybeans and advertised as health foods have much higher levels of phytate and are not worth eating.
Unfermented soy products are rich in enzyme inhibitors
When food is eaten, digestive enzymes such as amylase lipase and protease are secreted into the digestive tract to help break it down and free nutrients for assimilation into the body. The high content of enzyme inhibitors in unfermented soybeans interferes with this process and makes carbohydrates and proteins from soybeans impossible to completely digest. When foods are not completely digested because of enzyme inhibitors, bacteria in the large intestine try to do the job, and this can cause discomfort, bloating, and embarrassment. Anyone with naturally low levels of digestive enzymes such as elderly people would suffer the most from the enzyme inhibiting action of soy.
Soybeans can block production of thyroid hormone
Soybeans have a high content of goitrogens, substances that can block the production of thyroid hormone as well as cause goiter formation. Low thyroid activity plagues women in America, particularly middle-aged women. Thyroid hormone stokes the cellular furnaces, known as mitochrondia. When thyroid production is low, energy levels as well as body heat are also low. Low thyroid level is what makes old people move so slowly and seem like every action is a huge chore. Low thyroid means the action of the heart is reduced, resulting in lack of oxygen to the cells, a prime condition for cancer.
Genistein, an isoflavone found in soybeans, can also block thyroid production. Phytate can accentuate these effects because it binds up zinc and copper, leaving little of these important minerals available to make thyroid hormone.
A transport protein called GLUT1 is shut down by genistein. This protein sends glucose into the cells where it is used to generate energy. Slowing the transport of glucose means less energy production not only of thyroid hormone, but of every other action in the body.
Another way in which soy isoflavones reduce energy in the body is by inhibiting tyrosine kinases, enzymes involved in the transfer of energy from one molecule to another. These enzymes drive cell division, memory consolidation, tissue repair, and blood vessel maintenance and regeneration.
It is this action of regulating cell division that made genistein a popular substance for fighting cancer. When research on this anti-cancer effect of genistein became know, the soy industry feverishly developed products that would appeal to Western women looking for genistein. In the middle of all this excitement, little attention was paid to how the energy reducing effects of genistein lowered cellular energy in normal cells.
The benefits of genistein come at a high cost
Women have been encouraged to use high genistein soy products to alleviate symptoms of menopause and as a guard against bone loss and breast cancer. But given the full range of effects of genistein in the body, high consumption could result in age-related memory loss. Commercial soybean products offer genistein levels as high as 20 to 60 mg per serving. Asians are presented as an example of the benefits of eating soybean products because their incidence of breast cancer and osteoporosis is low. However, the Asian diet of fermented soybean products such as miso and tempeh includes only around 5 mg of genistein a day.
Genistein slows the growth of blood vessels to tumors, another action that makes it popular as a cancer fighter. However, it has the same effect on blood vessels serving normal cells. Eating a regular diet high in genistein could result in the starvation of healthy blood vessels, resulting in a reduced supply of oxygen to cells, setting up a cancer promoting situation.
In a graphic example of how genistein slows cellular energy, a study found that eating high levels of it slowed hair growth by 60 to 80 percent
A decade ago a study of 8,000 Asian men showed that those consuming the highest amounts of tofu had smaller brain size and nearly three times the rate of senile dementia as those who ate the lowest amounts. These results suggest that eating foods high in isoflavones such as soy protein isolates may accelerate the aging of the brain.
Fermentation releases nutrients and transforms soybeans into nutritious food
People filling up their shopping carts with raw or cooked soybeans, soy milk, and other non-fermented soybean products do not realize that the isoflavones they contain will not be available to their bodies. Most of the isoflavones in soy products are bound to carbohydrate molecules called glucosides. In this form genistein is actually called genistin. It is fermentation that transforms genistin into genistein. Many products in the U.S. do not distinguish between genistin and genistein on their labels.
Even with fermented soy foods, a little goes a long way. The nutrients found in miso, tempeh, and natto can be beneficial in the moderate amounts found in the typical Asian diet, but have the potential to do harm in higher amounts. In China and Japan, about an ounce of fermented soy food is eaten on a daily basis.
When fermented soy foods are used in small amounts they help build the inner ecosystem, providing a wealth of friendly microflora to the intestinal tract that can help with digestion and assimilation of nutrients, and boost immunity.
Dr. John Lee, author of several books on the health of women, recommended that women wishing to consume soy production eat only miso, tempeh, natto. Tofu can also be eaten provided it is accompanied by fish or some other protein source and some seaweed or kelp to replenish bound minerals. Eating small amounts of these foods will provide the cancer protective effects of genistein without causing the other potential problems of genistein. Dr. Lee recommended avoiding genistein and isoflavone supplements, and soy protein isolates.
Barbara L. Minton
Dr. John Lee, What Your Doctor May Not Tell You About Breast Cancer, Warner Books.
How Fermenting Takes the Allergy Out of Soy and Other Foods, bodyecology.com.