Cholesterol

The term “cholesterol” refers to a group of chemicals containing both protein and fat components (lipoproteins) that are present in every living cell. They are an essential component of all cells in the body of chickens, humans and indeed, all animals. They do not occur in plants. Cholesterol content of eggs became an important issue for consumers in the 1970's and 1980's when it was discovered that, among the human population, those with high cholesterol levels in their blood (usually referred to as “serum cholesterol”) were at greater risk of heart attacks and/or atherosclerosis. While this statistical connection is an important one in terms of human health, there have been crucial mistakes in its interpretation. There is effectively no link between the cholesterol most people consume in their diets, and their serum cholesterol levels.  Why do eggs contain so much cholesterol? The average egg, weighing 60 g, contains about 200 mg of cholesterol, all of it in the yolk. The reason for this is to supply the multiplying cells in the developing chick embryo with the cholesterol necessary for their correct function, until such time as the embryo can synthesize its own cholesterol from other components of the egg yolk.   “Good” and “Bad” Cholesterol These terms are used to describe the two main forms of cholesterol. High density lipoproteins, or “good cholesterol” (HDL) flows freely in the blood stream to the parts of the body metabolism where it is required for metabolic functions. Low density lipoproteins, “bad cholesterol” (LDL) tend to consist of larger particles which may accumulate in arteries, forming a plaque that may restrict the flow of blood. This may eventually result in increased blood pressure and possibly a heart attack. If clumps of the accumulated cholesterol become detached from the artery wall, they may cause blockage of smaller blood vessels, possibly resulting in strokes and heart attacks.  Cholestorol Content of Eggs  Please note: all cholesterol values are approximate   Eggs  Cholesterol (mg) Egg, whole, raw, 1 large 213mg Egg, whole, raw, 1 medium 187mg Egg, whole, raw, 1 extra large 247mg Egg yolk, raw, 1 large 213mg Egg white, raw, 1 large 0mg Egg, whole, fried, 1 large 211mg Egg, whole, hard-boiled, 1 large 212mg Egg substitute, liquid, 1/4 cup 1mg Source: www.annecolins.com What affects blood cholesterol if it's not the cholesterol we eat? There are many factors that influence serum cholesterol. As well as diet, they include lifestyle (primarily exercise or the lack of it), smoking, inheritance, body weight, and more. As far as diet is concerned, the most important factors are the consumption of saturated fats and trans-fats. Saturated fats are found primarily in animal products: animal fat, milk fat and cheese.  The fat in egg yolks is about 2/3 unsaturated and 1/3 saturated. Trans-fats are found in processed vegetable oils, frequently those used in preparation of fast foods. History of cholesterol research The research that first led to the cholesterol-phobia among the public was conducted early in the 20th century using rabbits. When fed relatively large amounts of cholesterol in their diet, serum cholesterol in treated rabbits rose to a very high level. The problem with this research was that in normal life, rabbits, which are by nature herbivorous, never encounter cholesterol, and therefore have no mechanism for digesting it or controlling serum levels beyond their normal range. Like all animals, rabbits produce for themselves all the cholesterol they need for normal metabolism. Other laboratory animals, such as rats and dogs, which are naturally omnivorous, have also been the subject of experiments with dietary cholesterol. However, in many cases, the levels fed were far in excess of those that would be encountered in a normal free-living existence, and totally overwhelmed the control mechanisms of the treated animals. All animals have a natural level of serum cholesterol that is maintained by an internal homeostatic mechanism.  When more cholesterol is consumed in food, less is produced internally, and vice versa. Within normal limits, this system naturally works well and maintains serum cholesterol at acceptable and non-dangerous levels. Studies of large groups of human subjects revealed the original results that high serum cholesterol levels were often associated with increased risk of cardiovascular disease. However, these data were unable to demonstrate the cause of the variation in serum cholesterol levels. In more recent studies, involving many thousands of subjects, the design allowed correction of data for such issues as age, heredity, and consumption of various foods. From these, we have been able to conclude that dietary cholesterol is not related to cardiovascular disease or heart attacks.Intervention studies, in which volunteers have varied  their intake of different foods, including eggs, have shown conclusively that eating eggs does not result in meaningful increases in serum cholesterol, or the risk of artery or heart disease.  Use of cholesterol-reducing drugs A very large number of people now use drugs to lower their serum cholesterol levels. These are prescription drugs, usually prescribed for people with serum cholesterol levels considered to place them in the “high-risk” category. The drugs are effective in lowering serum cholesterol levels; however their contribution to the ongoing health of their consumers in terms of avoidance of heart and artery diseases is difficult to determine. Lifestyle changes such as avoidance of smoking, maintenance of body weight in an acceptable range, regular exercise and diets low in saturated fat have been shown to be effective in reducing risk of disease.