According to data provided by the U.S. Food and Drug Administration (FDA), the safe intake of melamine is closely related to body weight. Therefore, larger adults who drink liquid milk containing melamine face a significantly lower risk of developing stones compared to infants and young children.
In the liquid milk found by the General Administration of Quality Supervision, Inspection and Quarantine of China (AQSIQ) to contain melamine, the melamine content was relatively low, with the highest being 8.6 milligrams per kilogram in Guangming Yogurt and Plain Yogurt. Guan Zhichen, director of the Department of Urology at Peking University Shenzhen Hospital, said: "Based on the standard that 37.8 milligrams of melamine per day is safe for a 60-kilogram adult, consuming the liquid milk found by AQSIQ to contain melamine, if not more than 2 liters per day, is relatively safe for the human body."
"If there are no symptoms such as difficulty urinating or back pain, adults do not need to worry excessively," Guan Zhichen said. He further explained that after the chemical melamine enters the human body, it is primarily excreted in three forms: directly through urine; forming a dihydrate compound; and forming stones with uric acid.
"Most of them are very small crystals," Guan Zhichen mentioned. If adults do not exhibit the aforementioned symptoms, there is no need to worry excessively; drinking more water in daily life is sufficient. However, if the body feels unwell, one should seek medical attention promptly. Doctors can confirm the diagnosis through an ultrasound examination and provide symptomatic treatment by adjusting the pH of the urine.
Generally speaking, adults can metabolize small amounts of melamine naturally through the kidneys, eliminating these trace toxic substances. However, Shenzhen is located in the subtropics with high temperatures year-round, so the body's moisture is mainly expelled through sweat, resulting in relatively less urine and a higher chance of developing kidney stones. Therefore, Guan Zhichen reminded the public that the simplest way to prevent urinary system problems is to drink more clear water.