Low cholesterol is not necessarily healthy! Blood lipid management requires balancing two key factors.

Low cholesterol is not a prerequisite for health: High cholesterol levels in the blood can lead to atherosclerosis, a major risk factor for coronary heart disease, myocardial infarction, and stroke. Therefore, controlling cholesterol levels is essential. However, excessively low cholesterol levels can also be harmful, especially in the elderly.

Blood lipids, primarily neutral fats including cholesterol, triglycerides, and lipoids, are essential substances for the body. They not only participate in energy production and storage but are also raw materials for the synthesis of adrenal cortex hormones, androgens, and estrogens. If blood lipid levels are too low, some physiological functions will be affected. Studies show that low cholesterol is not always good for the elderly. For those over 70 years of age, cholesterol levels below 4.16 mmol/L pose a risk comparable to levels above 6.24 mmol/L. Although the incidence of cerebral hemorrhage decreases with decreasing serum cholesterol levels, the incidence is actually higher when serum cholesterol levels are below 3.64 mmol/L. Therefore, low cholesterol is not necessarily a prerequisite for health.

The Function of Very Low-Density Lipoprotein (VLDL)
The primary function of VLDL is to transport endogenous triglycerides synthesized in the liver. Whether fatty acids transported from the blood to hepatocytes or those formed from glucose metabolism, triglycerides can be synthesized in hepatocytes. Within hepatocytes, triglycerides bind with apolipoprotein B100 (AB100), cholesterol, and other components to form VLDL, which is then released into the bloodstream. During a low-fat diet, the intestinal mucosa may also secrete some VLDL into the bloodstream. Most of the VLDL metabolized after entering the bloodstream is converted into low-density lipoprotein (LDL). Because these lipoproteins carry relatively little cholesterol and their particles are relatively large, they do not easily pass through the vascular endothelium. Therefore, normal VLDL does not contribute to arteriosclerosis and is not a major risk factor for coronary heart disease. However, since triglycerides account for 50%–70% and cholesterol for 8%–12% of VLDL, a significant increase in VLDL levels will lead to an increase in both triglyceride and cholesterol levels in the blood plasma.

Low-density lipoprotein (LDL) is derived from very low-density lipoprotein (VLDL). Its main function is to transport cholesterol to cells throughout the body, primarily to the liver for bile acid synthesis. While all lipoproteins carry a certain amount of cholesterol, LDL carries the most. Two-thirds of LDL in the body is absorbed into the liver and extrahepatic tissues via receptor-mediated pathways and then cleared through metabolism. The remaining one-third is cleared through a "scavenger" pathway. In this non-receptor pathway, macrophages bind to LDL and absorb the cholesterol within it, causing the cholesterol to remain inside the cell, creating "foam" cells. Therefore, LDL can enter arterial wall cells and carry cholesterol. Consequently, excessively high LDL levels can lead to atherosclerosis, putting individuals at risk of coronary heart disease.