Soy products have been heavily marketed in North America as safe and nutritious alternatives to animal-based protein products since the early 1990s. Soy protein powder is often used as a supplement by active people to maintain or build muscle. Most soy products and powders are made with soy protein isolate, or SPI, which is a protein-rich powder extracted from the waste product of soy oil manufacturing. SPI contains numerous compounds that are thought to be harmful to human health. The potential dangers of soy protein powders and products are becoming better understood.
Soy Protein Contains Phytic Acid
Although much has been said about soy in the Asian diet, historically and in modern times, Chinese and Japanese people consume soy products more as a condiment, and usually only fermented soybean products, such as tempeh, natto, miso and soy sauce. Unfermented soybean products, such as tofu, soy milk and soy protein supplements, contain large quantities of natural toxins.
Soy products contain high levels of phytic acid, which can block the uptake of essential minerals, such as calcium, magnesium, copper, iron and zinc, according to "Biochemical, Physiological and Molecular Aspects of Human Nutrition" (Reference 1). Thus, high consumption of soy protein powder could lead to mineral deficiency and potentially growth problems in children. Phytates found in soy powders interfere with zinc absorption most dramatically, which could negatively impact the immune system. Phytates are highly resistant to normal phytate-reducing techniques such as long, slow cooking.
Soy Protein Contains Trypsin Inhibitors
Other toxic substances in soy protein powder are enzyme inhibitors that block the action of trypsin and other enzymes needed for protein digestion. According to "Biochemistry of Human Nutrition," these trypsin inhibitors can produce serious gastric distress, reduced protein digestion and deficiencies with amino acid utilization. Some of the trypsin inhibitor content within SPI can be removed through high-temperature processing, but not all. In addition, trypsin inhibitor content of SPI, and therefore soy protein powder supplements, can vary as much as five-fold. Further, high-temperature processing used to reduce trypsin inhibitors has the side-effect of denaturing other proteins in soy, rendering them unsuitable for human digestion.
Soy Protein Contains Phytoestrogens
Soy protein powders also contain plant estrogens, called phytoestrogens, which disrupt the normal functioning of endocrine glands that produce hormones. According to "Nutrition and Public Health," phytoestrogens have the potential to cause infertility and hypothyroidism, in addition to promoting breast cancer in women. Men who take soy protein powders are especially sensitive to the hormonal effects of phytoestrogens, which suppress the production of testosterone and reduce the sex drive. The dramatic increase in gynecomastia, or breast enlargement, in boys and young men is thought to be partly related to estrogen mimicking hormones in soy products.
Soy Protein Contains Aluminum and Lysinoalanine
The production of SPI, found in many soy products, involves acid washing in aluminum tanks, which leaches aluminum particles into the final product. Aluminum is considered toxic to nerve tissue and possibly related to dementia-related diseases, such as Alzheimer's.
The processing of soybeans into SPI also produces a toxin called, lysinoalanine. According to "Contemporary Nutrition," it was concerns over lysinoalanine that led to the U.S. Food and Drug Administration's decision not to classify SPI as "Generally Recognized as Safe" for use as a human food additive.
References
- "Biochemical, Physiological and Molecular Aspects of Human Nutrition"; Martha Stipanuk; 2006
- "Biochemistry of Human Nutrition"; George Gropper; 2000
- "Nutrition and Public Health"; Sari Edelstein; 2006
- "Contemporary Nutrition"; Gordon M. Wardlaw; 2010
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