(1) The importance of nutrition to the cardiovascular system It is of great importance in maintaining the structure and function of the cardiovascular system. (1) Nutrition is an important source of energy: any mechanical work requires energy, and the heart has an extremely heavy and complex task, so it must convert the chemical energy in food into mechanical energy. The most important nutrient that normal cardiomyocytes take from the blood is free fatty acid (FFA) (about 67%), followed by glucose and lactate (about 17% each), in addition to amino acids, ketone bodies and pyruvate. If weighed by body weight, a normal human heart requires about 18g of fatty acids, 11g of glucose, 10g of lactic acid and 0.6g of pyruvate per day. This shows that the amount of nutrients taken in is considerable. The uptake and utilization of nutrients by cardiac muscle cells are influenced and regulated by various factors. The most important of these is the absolute concentration of nutrients in the blood. The higher the concentration, the greater the amount of uptake. For example, during fasting, glucose and insulin levels in the blood are low and adipose tissue releases large amounts of FFA, causing its concentration in the blood to increase. As a result, the uptake and utilization of FFA by cardiomyocytes is also significantly higher during fasting. Conversely, postprandial blood levels of glucose and insulin increase, while the level of FFA decreases, so that the myocardium mainly takes up and utilizes glucose. On the other hand, the lactate level in blood increases significantly during strenuous exercise, when it becomes the main energy supply substance. It can be seen that normal myocardial cells are highly adaptable to the uptake and utilization of various nutrients. However, in pathological conditions, for example, acute myocardial infarction, the adaptive capacity of ischemic cardiomyocytes to nutrients is significantly reduced. At this time, FFA is a harmful substance for it, while glucose becomes a good substrate for it. Therefore, in acute myocardial infarction, a drip of glucose and polarizing fluid (glucose with insulin and potassium) is beneficial. Like myocardial tissue, the arterial wall requires a constant supply of various nutrients from the blood, including proteins, glycolipids and cholesterol. Of these, cholesterol (including some triglycerides and phospholipids) enters the arterial wall in the form of lipoproteins (mainly LDL) and then enters the cell via the cell surface receptor pathway, where it is utilized as a structural component of the cell. This may also be one of the ways in which dietary cholesterol is removed. ② Nutrients are involved in several important physiological and biochemical processes in the cardiovascular system: In addition to a certain amount of energy, the diastole of the heart muscle requires the participation of certain metal ions, such as potassium, sodium and calcium. In addition, some vitamins and trace elements in food are also cofactors of several important enzyme systems in the metabolism of myocardial tissue and arterial walls. (2) Nutritional deficiencies or excesses on the cardiovascular system The normal structure and function of the cardiovascular system can be damaged by nutritional deficiencies or excesses, resulting in cardiovascular disease. Malnutrition, for example, foot disease caused by vitamin B1 deficiency, has been known for a long time. Some animal experiments in recent years have shown that dietary potassium, magnesium and chloride deficiencies can increase the susceptibility of cardiomyocytes to pathogenic factors, thus inducing primary necrotizing cardiomyopathy. Keshan disease, which occurs locally in China, is a cardiomyopathy of unknown cause and may be related to dietary deficiencies of certain trace elements, such as selenium, magnesium, and molybdenum. Magnesium deficiency can cause electrocardiographic abnormalities, promote selective myocardial calcification, and induce lethal myocardial spasm and tachyarrhythmias. Vitamin B6 and C deficiency can affect the structural integrity of the arterial wall. Dietary fiber deficiency is strongly associated with increased incidence of cardiovascular disease, diabetes and tumors. The cardiovascular system is more severely and commonly compromised by overnutrition than by deficiency. Excess intake of total calories, saturated fatty acids, cholesterol, and refined sucrose predispose to obesity, hyperlipidemia, and atherosclerosis, as described above. Excessive sodium intake is associated with the development of hypertension. In addition, in recent years, certain specific food components have been found, for example, excess erucic acid (22-carbon – enolic acid) can cause myocardial damage in animals. Individual vegetable oils also contain certain toxic substances that inhibit the activity of cholesterol ester hydrolase in the arterial wall, thus inducing atherosclerosis.