Because of its connection to cardiovascular disease, cholesterol has developed a bad reputation. Many physicians, patients and pharmaceutical advertisements speak of lowering cholesterol, and some people may even believe that the lower their cholesterol levels, the better. The truth is that cholesterol has several important functions in the body, and a careful balance must be maintained for good health.
Component of Cell Membranes
Cholesterol forms part of cellular membranes and, in this capacity, affects the permeability and function of these membranes. Because the cell membrane acts as a gatekeeper for the cell, cholesterol is involved in allowing or preventing critical nutrients from entering the cell, and this in turn affects cellular function. It is worth noting that myelinated components of the brain and central nervous system are particularly abundant in cholesterol.
Precursor for Bile Acids
Bile acids are synthesized from cholesterol in the liver and facilitate the absorption of dietary fats and fat-soluble vitamins.
Precursor for Steroid Sex Hormones
Although they have very different functions, the sex hormones progesterone, estrogen and testosterone all are derived from and structurally related to cholesterol. Cholesterol, then, is indirectly involved in the many actions of these hormones, including regulation of metabolism and synthesis of protein and body tissue, as well as regulation of the menstrual cycle, improvement of skin tone, prevention of bone loss and reduction of heart attack risk in women.
Precursor for Other Hormones
Several other hormones are synthesized from cholesterol. In addition to small amounts of sex hormones, the adrenal glands produce corticosteroids (including cortisol and cortisone) as well as mineralcorticoids (such as aldosterone) from cholesterol. Cortisol exerts several functions within the body: It increases blood glucose levels by stimulating glucose formation from non-carbohydrate precursors; it inhibits immune and inflammatory responses throughout the body; and it decreases calcium levels in the blood, among other things. Aldosterone is the hormone largely responsible for fluid balance in the blood via sodium retention and, to a lesser degree, potassium and hydrogen loss. The production of these hormones depends on cholesterol.
Raw Material for Vitamin D
Cholesterol is also a precursor for vitamin D within the human body. Ultraviolet light from the sun converts a form of cholesterol in the skin into a form of vitamin D. Cholesterol therefore is implicated in the many roles of vitamin D in the body, including maintenance of calcium balance, regulation of cell differentiation and proliferation and regulation of immune function.
References
- "Advanced Nutrition and Human Metabolism;" Sareen Gropper, Jack Smith and James Groff; 2005
- "Alternative Medicine, The Definitive Guide;" Burton Goldber; 2002
- "Biochemistry with Clinical Correlations"; Thomas Devlin; 2002
