The light diet is a special diet for hematology, which is characterized by lightness but not low salt. The light diet is the most basic diet for patients with hematologic diseases, but the light diet required by patients with hematologic diseases has a very different understanding and usage of “light” than the “light” in normal people’s general diet. Before we talk about the light diet, let us first recognize salt. The National Standard for Table Salt (GB5461-2000) states that table salt is crystallized sodium chloride, which is used for food. The chemical index of refined salt is ≥99.1% wet basis sodium chloride. Dietary sodium mainly exists in table salt, salt salt salty taste mainly from sodium ions, the minimum requirement of sodium for the human body is about 200mg, equivalent to 0.5 grams of table salt (1 gram of table salt = 393mg of sodium). The sodium content of common table salt is about 40% by weight. Chlorine often exists in the form of chloride, in the form of sodium chloride (salt) intake, absorbed through the gastrointestinal tract, into the human body contains about 100 grams of chlorine, accounting for 0.15% of body weight. Sodium ions and chloride ions are mainly excreted through the kidneys via the urine, and the amount of sodium excreted by the kidneys is balanced with the amount ingested. Salt is the most important seasoning although its dosage is very small, but the role of the human body can not be ignored, maintaining the body’s acid-base balance. First of all, a light diet is not the same as a vegetarian diet (a complete vegetarian diet can lead to protein and fatty acid deficiencies). A light diet is a diet that is light in flavor and maintains the original taste of the food under the premise of a well-balanced diet. A light diet is also known as a “five low diet”, i.e. low salt, low sugar, low fat, low cholesterol and low stimulation. The light diet is also known as “four low diet”, i.e., low sugar, low fat, low cholesterol, low stimulation, but not low salt. Sodium is a component of salt, and normal people do not accumulate sodium in the body, so the diet is characterized by the need to add more salt (with the exception of those who have high blood pressure, dehydration, and abnormal renal function). After radiotherapy and hematopoietic stem cell transplantation, the vast majority of patients with poor appetite, dietary intake is greatly reduced, salt intake is even less, the maintenance of human blood sodium, salt is the only source of our patients can not consume salted and processed preparation of outsourced food, diarrhea, vomiting, fasting, poor diet, rehydration, diuretics, water retention, hypokalemia, aldosterone reduction and so on are all the cause of the human body’s blood sodium content lower or imbalanced, so a low-salt diet is not recommended. Low fat: Excess fat is the culprit of obesity, coronary heart disease, high blood pressure and certain cancers, but a low fat diet is the most basic diet for patients with hematologic diseases. Low cholesterol: chemotherapeutic drugs are easy to cause damage to liver and kidney function, eat less animal food containing high cholesterol, one egg per day is enough, choose lean meat for meat, do not eat animal offal, crab roe and so on. Low Sugar: Eat less refined sugar and sweets, and blood tumor advocates low sugar diet. Low stimulation: eat less spicy food, which is easy to cause gastrointestinal discomfort, and it is a kind of malignant stimulation for patients with oral rejection. Patients with hematological diseases have poor appetite, relatively low sodium intake, coupled with severe loss of sodium caused by diarrhea and other reasons, hyponatremia is easy to occur. For hematological patients with combined hyponatremia, high sodium vegetables such as rape, celery, fennel, coriander, radish, cabbage, spinach, etc., can be chosen, and more animal protein foods can also be chosen because the natural sodium content of animal protein is much higher than that of vegetables and grains. Although high sodium foods are the best preventive measure against low sodium, salt pickles are absolutely forbidden. Patients with hematologic disorders are in a unique situation, so the Nutrition Institute suggests a “four lows” light diet to avoid hyponatremia. When the patient appears lethargy, indifference, fainting when standing up, muscle cramps, nausea, vomiting and other clinical manifestations of hyponatremia, remember to consult a doctor in a timely manner, of course, salt intake is not the higher the better, in addition to the increase in blood pressure will lead to an increase in urinary calcium intake. Appropriate light diet can reduce the burden on the patient’s kidneys and lay the foundation for subsequent treatment, but a light diet is not conducive to the patient’s recovery, and will affect the patient’s digestion and absorption of food.