Soy milk is made from soybeans through processes such as soaking, grinding, and filtering. It not only possesses many of the nutritional advantages of soybeans but also surpasses soybeans in certain aspects.
Soy milk contains a large amount of soy protein, which is a high-quality plant protein containing various essential amino acids, particularly a high lysine content, which can compensate for the lysine deficiency in rice and flour. The digestibility of protein in soy milk is about 20% higher than that of raw soybeans. Soy milk is also high in fat and contains relatively rich essential fatty acids, which help promote growth and development and protect cardiovascular function. Additionally, it contains a considerable amount of calcium, iron, and B vitamins. Therefore, the nutritional value of soy milk is indeed very high.
In China, soy milk is often used as a breast milk substitute for infants over 3 months old, or as a nutritional supplement for those allergic to milk protein and for the elderly. However, some people who consume unboiled soy milk may suffer from food poisoning. What is the reason for this?
Soybeans contain saponins, which can cause nausea, vomiting, and indigestion. They also contain some enzymes and other substances, such as trypsin inhibitors, which can reduce the human body's ability to digest protein; lectins can cause blood clotting; and urease glycosides can interfere with iodine metabolism and inhibit the synthesis of thyroid hormones, leading to compensatory goiter. However, after being thoroughly cooked, these harmful substances are completely destroyed, making soy milk harmless to the human body. Iodine is now also added to the formulas of soy-based infant formula to mitigate the side effect of goiter.
Finally, it must be noted that when boiling soy milk, a "false boil" phenomenon often occurs. It is essential to stir it thoroughly with a spoon until it truly boils and is cooked through. Only then can it be fed to children to avoid soy milk poisoning.