We earlier mentioned that the cholesterol level in an individual is directly linked to HDL and LDL the blood plasma. Meanwhile, the concentrations of these agents (HDL and LDL) are, in turn, determined by the nature of our diet.
In general, saturated fatty acids, which are found primarily in animal foods, tend to elevate LDL and total blood cholesterol. However, the most cholesterol-raising saturated fatty acids (lauric, myristic, and palmitic acids) can come from both plant and animal sources, while stearic acid, derived from animal fat as well as from cocoa butter, is considered neutral, neither raising nor lowering blood cholesterol levels.
In general, saturated fatty acids, which are found primarily in animal foods, tend to elevate LDL and total blood cholesterol. However, the most cholesterol-raising saturated fatty acids (lauric, myristic, and palmitic acids) can come from both plant and animal sources, while stearic acid, derived from animal fat as well as from cocoa butter, is considered neutral, neither raising nor lowering blood cholesterol levels.
When saturated fatty acids are replaced by unsaturated fatty acids—either monounsaturated or polyunsaturated—LDL and total blood cholesterol will be reduced, an effect largely attributed to the reduction in saturated fat. However, polyunsaturated fatty acids tend to lower HDL cholesterol levels, while monounsaturated fatty acids tend to maintain them. The major monounsaturated fatty acid in animals and plants is oleic acid; good dietary sources are olive oil, canola oil, and high-oleic safflower oils, as well as avocados, nuts, and seeds. Historically, the low death rate from Cardio - Vascular Disease in populations eating a traditional Mediterranean diet has been linked to the high intake of olive oil in those regions, although the plentiful supply of fruits and vegetables could also have an impact.
The two types of polyunsaturated fatty acids found in foods are omega-3 fatty acids and omega-6 fatty acids. These have been found to be effective against high cholesterol levels. Populations that consume foods containing high levels of these acids (e.g. the Eskimos) have low cardiovascular disease rates. Linoleic acid, the primary omega-6 fatty acid in most diets, is widespread in foods; the major source is vegetable oils such as sunflower oil, safflower oil, and corn oils. Omega-3 fatty acids may also protect the heart and blood vessels by lowering blood pressure, reducing blood clotting, preventing irregular heart rhythms, and acting as anti-inflammatory agents. Other foods high in omega-3 fatty acids are fatty fish such as salmon, herring, sardines, mackerel, and tuna.
Flaxseed is an excellent source of alpha-linolenic acid, which the body can convert to omega-3 fatty acids. Other sources of omega-3 fatty acids include walnuts, hazelnuts, almonds, canola oil, soybean oil, dark green leafy vegetables such as spinach, and egg yolk. A diet high in polyunsaturated fatty acids may increase LDL lipid oxidation and thereby accelerate atherosclerosis; therefore, it should be accompanied by increased intakes of vitamin E, an antioxidant. Fish oil supplements are not advised without medical supervision because of possible adverse effects, such as bleeding.
Cholesterol in food (dietary cholesterol) is distinguishable from cholesterol in the blood stream, and they are often confused. Foods of animal origin are the only known sources of dietary cholesterol. It is particularly high in egg yolk and organ meats. Cholesterol in the diet raises LDL cholesterol, but not as much as saturated fatty acids do. However, because cholesterol is synthesized by the body, none is required in the diet.
Ingestion of soluble fibre, a component of dietary fibre (indigestible plant material), lowers LDL and total blood cholesterol levels and has been linked to reduced death rates from cardiovascular disease. Foods like whole oats, barley, legumes, some vegetables, and fruits, particularly apples, plums, apricots, blueberries, strawberries, and citrus fruits, are rich in fibre. Fibre supplements may also be recommended.
It has been discovered that light to moderate alcohol intake (up to two drinks per day for men and one drink per day for women) is associated with reduced risk cardiovascular disease, primarily because of the ability of alcohol to raise HDL levels, and possibly because it helps prevent blood clot formation.
Intake of dietary sodium (salt) is significantly associated with mortality from stroke and heart disease, but only in overweight individuals, who may have an increased sensitivity to dietary sodium. Salt intake also appears to have a direct effect on risk of stroke beyond its effect on blood pressure, which itself influences stroke risk. But, diets rich in potassium reduce the risk of stroke.