Cholesterol is a member of the group of lipids known as sterols; a soft waxy substance manufactured in the body for a variety of purposes and also found in animal-derived foods.
High blood cholesterol, particularly when the ratio of LDL to HDL is high, predicts cardiovascular disease (CVD). An increased risk of heart disease exists when an LDL to HDL ratio greater than 5 to 1 in men or 4.5 to 1 in women. A population with average blood cholesterol 10 percent lower than another will suffer 33 percent less CVD; a 30 percent difference in blood cholesterol predicts a rate of CVD that is lower by four times. How does diet relate to high blood cholesterol? The currently accepted hypothesis has two parts: (1) that high blood cholesterol is at least partly caused by a diet high in saturated fat; and (2) that reducing the saturated fat in the diet will lower blood cholesterol and will reduce the rate of CVD.
Both parts of this hypothesis have some strong support. Regarding the first part, wherever in the world diets are high in saturated fat, blood cholesterol is high and heart disease takes a great toll on health and life. Conversely, wherever dietary fat consists mostly of monounsaturated fats, blood cholesterol and the rate of death from heart disease are low.
The second part of the hypothesis, that lowering saturated fat intakes will lead to lower blood cholesterol and reduced heart disease risks, is well-accepted by most authorities, and is supported by the bulk of research. Most agree that for people living in the United States and Canada, the percentage of calories from saturated fat in the diet should not be more than 10 percent.
Recommendations for U.S. and Canada citizens also urge that total fat be held to no more than 30 percent of calories, and that the cholesterol intake from food be limited to 300 milligrams a day. These measures may be important for some people; but perhaps not for all. The links between total fat and dietary cholesterol on the one hand, and blood cholesterol (and CVD) on the other, are not as firm as those between saturated fat, blood cholesterol, and CVD. Data on the people of Greece, France, and other Mediterranean countries illustrate that diets high in total fat can coexist with low rates of heart disease. The key difference between their high-fat diets and those of U.S. and Canadian peopleís high-fat diets seems to be that theirs are high in monounsaturated, rather than saturated, fats.
A valid question is whether Mediterranean peoples may be more naturally resistant to heart disease, but research has shown that this is not the case. People who move from one place to another and who adopt the dietary habits of the new location demonstrate heart disease rates typical of people born in the new location. Other factors, may, however, explain the Mediterranean peopleís low heart disease rates. They are more physically active than people in the United States and Canada. They also consume more fruits and vegetables, less meat and animal fat, more olive oil, and a greater percentage of each dayís calories early in the morning. Donít discount the effects of meal timing on heart disease risk. A small by significant improvement in blood lipids is seen in those with a meal pattern of taking frequent small meals each day, rather than the standard few large meals.Total Cholesterol:
In addition to diet, some types of exercise are effective in lowering LDL and in raising HDL concentrations. Particularly aerobic exercise, when combined with a low-fat diet, may help to reverse CVD. There is some evidence to suggest that some forms of weight training also may elevate blood HDL concentrations somewhat, if undertaken regularly. Even light exercise, such as walking and gardening at intervals throughout the day improves the odds against heart disease considerably if consistently pursued.