Once upon a time, we didn’t know anything about fat except that it made foods tastier. We cooked our food in lard or shortening. We spread butter on our breakfast toast and plopped sour cream on our baked potatoes. Farmers bred their animals to produce milk with high butterfat content and meat “marbled” with fat because that was what most people wanted to eat. But ever since word got out that diets high in fat are related to heart disease, things have become more complicated. Experts tell us there are several different kinds of fat, some of them worse for us than others. In addition to saturated, monounsaturated and polyunsaturated fats, there are triglycerides, trans fatty acids, and omega 3 and omega 6 fatty acids.

Cholesterol is sort of a “cousin” of fat. Both fat and cholesterol belong to a larger family of chemical compounds called lipids. All the cholesterol the body needs is made by the liver. It is used to build cell membranes and brain and nerve tissues. Cholesterol also helps the body produce steroid hormones needed for body regulation, including processing food, and bile acids needed for digestion. People don’t need to consume dietary cholesterol because the body can make enough cholesterol for its needs. But the typical U.S. diet contains substantial amounts of cholesterol, found in foods such as egg yolks, liver, and meat, some shellfish, and Many people are confused about the effect of dietary fats on cholesterol levels.

Polyunsaturated and monounsaturated fats do not promote the formation of artery-clogging fatty deposits the way saturated fats do. Some studies show that eating foods that contain these fats can reduce levels of LDL-cholesterol in the blood. Polyunsaturated fats, such as safflower and corn oil, tend to lower both HDL- and LDL-cholesterol. Edible oils rich in monounsaturated fats, such as olive and canola oil, however, tend to lower LDL-cholesterol without affecting HDL levels.

In 1908, scientists first observed that rabbits fed a diet of meat, whole milk, and eggs developed fatty deposits on the walls of their arteries that constricted the flow of blood. Narrowing of the arteries by these fatty deposits is called atherosclerosis. It is a slowly progressing disease that can begin early in life but not show symptoms for many years. In 1913, scientists identified the substance responsible for the fatty deposits in the rabbits’ arteries as cholesterol. In 1916, Cornelius de Langen, a Dutch physician working in Java, Indonesia, noticed that native Indonesians had much lower rates of heart disease than Dutch colonists living on the island. He reported this finding to a medical journal, speculating that the Indonesians’ healthy hearts were linked with their low levels of blood cholesterol.

Omega-6 polyunsaturated fatty acids have also been found in some studies to reduce both LDL- and HDL-cholesterol levels in the blood. Linoleic acid, an essential nutrient (one that the body cannot make for itself) and a component of corn, soybean and safflower oil, is an omega-6 fatty acid. At one time, many nutrition experts recommended increasing consumption of monounsaturated and polyunsaturated fats because of their cholesterol-lowering effects. Now, however, the advice is simply to reduce dietary intake of all types of fat. (Infants and young children, however, should not restrict dietary fat.)

A Healthier You Once upon a time, everyone didn’t know much about fat except that it made foods richer. everyone cooked our food in lard or shortening. everyone spread butter on our breakfast toast and poured sour cream on our jacket potatoes. Farmers grew their herds to make milk with high butterfat content and meat “marbled” with fat because that was what most people wanted to eat. A Healthier You

Fats are a group of chemical compounds that contain fatty acids. Energy is stored in the body mostly in the form of fat. Fat is needed in the diet to supply essential fatty acids, substances essential for growth but not produced by the body itself. There are three main types of fatty acids: saturated, monounsaturated and polyunsaturated. All fatty acids are molecules composed mostly of carbon and hydrogen atoms. A saturated fatty acid has the maximum possible number of hydrogen atoms attached to every carbon atom. It is therefore said to be “saturated” with hydrogen atoms. Some fatty acids are missing one pair of hydrogen atoms in the middle of the molecule. This gap is called an “unsaturation” and the fatty acid is said to be “monounsaturated” because it has one gap. Fatty acids that are missing more than one pair of hydrogen atoms are called “polyunsaturated.”

Cholesterol is transported in the bloodstream in large molecules of fat and protein called lipoproteins. Cholesterol carried in low-density lipoproteins is called LDL-cholesterol; most cholesterol is of this type. Cholesterol carried in high-density lipoproteins is called HDL-cholesterol. A person’s cholesterol “number” refers to the total amount of cholesterol in the blood. Cholesterol is measured in milligrams per decilitre (mg/dl) of blood. (A decilitre is a tenth of a litre.)

Polyunsaturated and monounsaturated fats do not promote the formation of artery-clogging fatty deposits the way saturated fats do. Some studies show that eating foods that contain these fats can reduce levels of LDL-cholesterol in the blood. Polyunsaturated fats, such as safflower and corn oil, tend to lower both HDL- and LDL-cholesterol. Edible oils rich in monounsaturated fats, such as olive and canola oil, however, tend to lower LDL-cholesterol without affecting HDL levels.

In 1908, scientists first observed that rabbits fed a diet of meat, whole milk, and eggs developed fatty deposits on the walls of their arteries that constricted the flow of blood. Narrowing of the arteries by these fatty deposits is called atherosclerosis. It is a slowly progressing disease that can begin early in life but not show symptoms for many years. In 1913, scientists identified the substance responsible for the fatty deposits in the rabbits’ arteries as cholesterol. In 1916, Cornelius de Langen, a Dutch physician working in Java, Indonesia, noticed that native Indonesians had much lower rates of heart disease than Dutch colonists living on the island. He reported this finding to a medical journal, speculating that the Indonesians’ healthy hearts were linked with their low levels of blood cholesterol.

Omega-6 polyunsaturated fatty acids have also been found in some studies to reduce both LDL- and HDL-cholesterol levels in the blood. Linoleic acid, an essential nutrient (one that the body cannot make for itself) and a component of corn, soybean and safflower oil, is an omega-6 fatty acid. At one time, many nutrition experts recommended increasing consumption of monounsaturated and polyunsaturated fats because of their cholesterol-lowering effects. Now, however, the advice is simply to reduce dietary intake of all types of fat. (Infants and young children, however, should not restrict dietary fat.)