Because raw soy milk contains a substance called saponin, if consumed uncooked, it can irritate the gastrointestinal mucosa and lead to poisoning symptoms: nausea, vomiting, abdominal pain, diarrhea, loss of appetite, and fatigue.
When raw soy milk is heated to 80°C~90°C, a large amount of white foam will appear. This is a "false boiling" phenomenon, and at this temperature, the saponin in the soy milk has not yet been destroyed.
The correct method for boiling soy milk is: after the "false boiling" phenomenon appears, continue heating for 3-5 minutes until the foam completely disappears.
Because soy milk is considered "cool" in nature, people with a "cold stomach" constitution, such as those who often belch or burp after meals, and those with a "spleen deficiency," such as those with diarrhea or bloating, should not drink it. During its metabolic process in the body, soy milk produces nucleic acids and uric acid, so patients with increased uric acid should not drink it. Furthermore, patients with poor kidney function, renal failure, or uremia should also avoid soy milk, as the plant protein in it can increase the burden on the kidneys. Soy milk should also not be taken with medicine, especially not with antibiotics, because some antibiotics can destroy the nutritional components of soy milk, and the iron and calcium in it can reduce or neutralize the effectiveness of the medication.
Additionally, soy milk should not be stored in a thermos, as this can promote bacterial growth and cause the protein in the soy milk to denature. Also, adding sugar while boiling soy milk will cause precipitates to form, so sugar should be added after removing it from the heat. It is particularly important to note that brown sugar should absolutely not be added to soy milk, because the organic acids in brown sugar will bind with the protein to form precipitates, which not only deprives the soy milk of its nutritional value but is also detrimental to health.