Fats and Cholesterol
Fat is required for the production of cell membranes, blood lipids (body fat), bile (fat emulsifier), steroids and vitamin D. Fats molecules are made up of glycerol and fatty acids.
Body fat is also instrumental in body temperature regulation as insulation. Minimum body fat percentages of 7% for men and 12% for women are recommended. Fats are also utilized for the transport and absorption of fat soluble vitamins. In addition, fats are the only source of linoleic acid which is required for skin growth and maintenance. Minimum daily requirement for unsaturated fat is 10 grams and 15 grams is preferred.
Fats are digested by the enzyme lipase in the small intestines with the assistance of bile salts as emulsifiers. They are then transported through the bloodstream with the assistance of lipoproteins (fat + protein coating + phospholipids) and stored as triglycerides (glycerol + 3 particles of fatty acids) in fat cells. They are then released into the bloodstream as fatty acids when energy is required.
The fatty acids travel through the bloodstream and are combined with glucose to burn the combination as energy. The combination of fatty acids and glucose is necessary for aerobic energy production. The anaerobic system uses mainly glucose and phosphagen, which is limited in its ability to produce energy. Further, lactic acid is one of the by products causing the burning sensation after a hard workout. Inadequate carbohydrate availability will result in incomplete fat metabolization producing unused lipids called ketones and leading to a chemical imbalance in the blood known as ketosis. Organ and muscle tissue may be metabolized to provide glucose from the breakdown of protein. Most of the weight loss that occurs by severe carbohydrate restricted diets are from water loss as the kidneys attempt to rid the body of the ketones.
Fat is essential to survival. A fat-less diet can lead to severe problems. Linoleic acid, an essential fatty acid, is used by the liver to manufacture arachidonic acid. This super polyunsaturated fat is used in cell membranes along with protein. When needed, this fatty acid is converted into a group of chemicals that regulate blood pressure, contractions in childbirth, blood clotting, peristalsis (gut motion), and the immune system. These chemicals are short lived and are manufactured locally as needed.
Cholesterol belongs to the same chemical family as steroids and is related to fat. It is important for the production of cell membranes, myelin sheaths around nerves, sex hormones, bile, and vitamin D.
Dietary cholesterol is the cholesterol consumed from the diet. Blood Serum cholesterol is the amount of cholesterol circulating in the bloodstream. The two are not closely related. Some people consume large quantities of dietary cholesterol and have a low serum cholesterol level. And, conversely, some people have high blood serum levels and consume very little dietary cholesterol. Conversion from dietary to blood serum cholesterol varies for each person and ranges from 20% to 90% of the amount consumed.
Blood serum cholesterol levels should remain below 200 mg per deciliter to be considered "normal" according to recent studies. This number represents only 10% of the total amount of cholesterol in the body. The rest is contained in cell membranes and other body tissues. The National Cholesterol Education Program recommends a dietary cholesterol consumption of no more than 300 mg per day. The body requires no intake of cholesterol but manufactures all the cholesterol it needs from dietary fat and produces about 1000 mg per day.
There are basically two types of Cholesterol transport systems, Low Density Lipoproteins (LDL) and High Density Lipoproteins (HDL). Each type is a fat carrying protein. LDLs, the bad cholesterol carrier, transports cholesterol to the cells and are associated with atherosclerosis or hardening of the arterial walls. HDLs, the good cholesterol carrier, transports cholesterol to the liver where it is processed for excretion or broken down for other uses. Monosaturated and Polyunsaturated fats lower LDL levels and increase HDLs whereas Saturated fats increase LDL levels. The goal is therefore to minimize the LDL cholesterol by reducing the dietary intake of saturated fats. The food label may tout "no cholesterol" but the body manufactures cholesterol from saturated fats.
Arteriosclerosis is a condition where the arteries become occluded. This is caused by a lesion which develops just under the inner lining of the arterial wall. This swelling, composed of fibrous protein, accumulates LDL carried cholesterol as blood platelets begin to stick to the damaged area. This accumulation reduces the inner diameter of the artery and subsequently leads to a decreased flow of blood through the artery. The platelets continue to accumulate at the injured site until a clot is formed, blocking all blood flow to the heart. The area of the heart normally being fed by this artery becomes injured. This is known as a heart attack.
Cardiovascular health is a result of proper diet and exercise. Genetics may predispose someone to high blood pressure or heart disease, however, diet, exercise and medication can lessen the impact and improve longevity.