Most people have learned something about cholesterol, and many of us have been to the doctor for a blood test to learn our cholesterol “number.” Now, however, it turns out that there’s more than one kind of cholesterol, too. Almost every day there are newspaper reports of new studies or recommendations about what to eat or what not to eat: Lard is bad, olive oil is good, margarine is better for you than butter– then again, maybe it’s not. 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.
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.)
Another misconception is that people can improve their cholesterol numbers by eating “good” cholesterol. In food, all cholesterol is the same. In the blood, whether cholesterol is “good” or “bad” depends on the type of lipoprotein that’s carrying it.
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.
People living on the Greek island of Crete have very low rates of heart disease even though their diet is high in fat. Most of their dietary fat comes from olive oil, a monounsaturated fat that tends to lower levels of “bad” LDL-cholesterol and maintain levels of “good” HDL-cholesterol. The Inuit, or Eskimo, people of Alaska and Greenland also are relatively free of heart disease despite a high-fat, high-cholesterol diet. The staple food in their diet is fish rich in omega-3 polyunsaturated fatty acids. Some research has shown that omega-3 fatty acids, found in fish such as salmon and mackerel as well as in soybean and canola oil, lower both LDL-cholesterol and triglyceride levels in the blood. Some nutrition experts recommend eating fish once or twice a week to reduce heart disease risk. However, dietary supplements containing concentrated fish oil are not recommended because there is insufficient evidence that they are beneficial and little is known about their long-term effects.
A Healthier You Quite a few years back, we didn’t know anything about fat except that it made foods richer. We cooked our food in lard or shortening. We spread butter on our morning toast and poured 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. A Healthier You
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