Cholesterol: A FastFacts Look At An Essential Substance
How much do you know about cholesterol?
Though much-maligned by Big Pharma, cholesterol is essential to our life and health.
Cholesterol is a fatty, waxy substance found in the cell membranes and transported in the blood plasma of all animals.
- It is an essential component of our cell membranes where it builds and maintains cell membranes and establishes proper membrane permeability and fluidity for normal cellular function.
- It plays a central role in many biochemical processes, such as the synthesis of steroid hormones.1
- Cholesterol is synthesized in virtually all cells, and it is possible for significant amounts to be absorbed from the diet. In practice, most of the cholesterol in the body is synthesized internally; only some is absorbed in the diet.
- Cholesterol is more abundant in tissues which either synthesize more, or have more abundant, densely-packed membranes, for example, the liver, spinal cord and brain.
- About 20–25% of total daily production of cholesterol occurs in the liver which produces about 1 gram per day, in bile. Bile, which is stored in the gallbladder and released to help digest fats, is important for the absorption of the fat soluble vitamins, vitamins A, D, E, and K. Other sites of high synthesis rates include the intestines, adrenal glands and reproductive organs.
- Of the cholesterol released into the intestines in bile, 92–97% is reabsorbed in the intestines and recycled by the liver.
- For a person of about 150 pounds, typical total body content is about 35 g, typical daily internal production is about 1 g and typical daily dietary intake is 200–300 mg in the United States and societies with similar dietary patterns.
- Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the control mechanisms involved are only partly understood. A higher intake from food leads to a net decrease in endogenous production, while lower intake from food has the opposite effect.
- Cholesterol is the main precursor of vitamin D and of the steroid hormones, which include cortisol and aldosterone (in the adrenal glands) and progesterone, estrogens, and testosterone (the sex hormones), and their derivatives. It provides the basic structure of all the steroids.
- In myelin, cholesterol envelopes and insulates nerves, helping greatly to conduct nerve impulses.
- Some research indicates that cholesterol may act as an antioxidant.2
- Recently, cholesterol has also been implicated in cell signaling processes, assisting in the formation of lipid rafts in the plasma membrane. It also reduces the permeability of the plasma membrane to protons (positive hydrogen ions) and sodium ions.3
Despite the widely-proclaimed role of cholesterol in cardiovascular disease, some studies have shown an inverse correlation between cholesterol levels and mortality in people over 50 years of age an 11% increase overall and 14% increase in CVD mortality per 1 mg/dL per year drop in cholesterol levels. In the Framingham Heart Study, researchers attributed this to the fact that people with severe chronic diseases or cancer tend to have below-normal cholesterol levels.4 This explanation is not supported by the Vorarlberg Health Monitoring and Promotion Program, in which men of all ages and women over 50 with very low cholesterol were increasingly likely to die of cancer, liver diseases, and mental diseases. This result indicates that the low cholesterol effect occurs even among younger people, and contradicts the previous belief that in older people lower cholesterol is an indicator of frailty occurring with age.5
- 1.) Stryer, Lubert (1995). Biochemistry (4th ed. ed.). New York: W.H. Freeman & co.. pp. 280, 703. ISBN 0-7167-2009-4.
- Smith LL (1991). “Another cholesterol hypothesis: cholesterol as antioxidant”. Free Radic. Biol. Med. 11 (1): 47–61. doi:10.1016/0891-5849(91)90187-8. PMID 1937129.
- Haines TH (2001). “Do sterols reduce proton and sodium leaks through lipid bilayers?”. Prog. Lipid Res. 40 (4): 299–324. doi:10.1016/S0163-7827(01)00009-1. PMID 11412894.
- Anderson KM., Castelli WP, Levy D. (1987). “Cholesterol and mortality. 30 years of follow-up from the Framingham study”. JAMA 257: 2176–80. doi:10.1001/jama.257.16.2176. PMID 3560398
- Ulmer H., Kelleher C., Diem G., Concin H. (2004). “Why Eve is not Adam: prospective follow-up in 149650 women and men of cholesterol and other risk factors related to cardiovascular and all-cause mortality”. J Women’s Health (Larchmt) 13: 41–53. doi:10.1089/154099904322836447. PMID 15006277
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