Coronary heart disease (CHD) is the leading cause of death in the United States and other affluent countries of the world. In most instances, CHD results from the obstruction of coronary blood vessels by atherosclerosis or thrombosis.
Atherosclerosis is characterized by a thickening of artery walls, which causes the arteries to become narrower.
These lesions (areas affected by disease or injury) eventually accumulate lipid (mostly cholesterol) and become calcified. They are also known as atherosclerotic plaques.
Thrombosis is the formation of a blood clot caused by the aggregation of blood platelets. The formation of a circulating blood clot can result in the blockage of a blood vessel, especially at a site where severe narrowing has already occurred because of atherosclerosis. When these events occur in blood vessels leading to the heart, they cab cause a heart attack. If they occur in the vessels leading to the brain, they cause a stroke.
Many risk factors, both genetic and environmental, contribute to the development of coronory heart disease (CHD).
The three notable risk factors are:
A. Cigarette smoking
B. High blood pressure
C. Elevated blood cholesterol levels
Other risk factors include; family history of premature CHD, male gender, advanced age, obesity, diabetes mellitus and lack of physical exercise.
Not only is the multifactorial nature of CHD recognised by numerous federal government agencies and health professionals, but a high blood cholesterol level has been regarded as one of the major modifiable risk factors.
Desirable total blood cholesterol levels: 180-200mg/dl
Borderline-high values: 200-239mg/dl
High total cholesterol levels: 240mg/dl and above
Blood lipid-protein agglomerates, collectively called lipoproteins, have been associated with CHD risk.
The four classes of lipoproteins based on density and lipid and apolipoprotein composition include:
Chylomicrons
Very low-density lipoproteins (VLDL)
Low density lipoproteins (LDL)
High density lipoproteins (HDL)
Chylomicrons, VLDL's and LDL's contain a protein called apoprotein B (Apo B). this protein is atherogenic i.e. pormotes atherosclerosis.
HDL's on the other hand contain a protein called Apo A1 which is anti-atherogenic i.e. does not promote atherosclerosis. It prevents oxidation of LDL's. Inhibition of LDL oxidation slows the development of atherosclerosis.
An elevated level of blood LDL cholesterol, the major cholesterol-carrying lipoprotein, is associated with increased risk of CHD. In contrast, a low level of HDL cholesterol contributes to a major CHD risk factor.
Whether or not a high blood triglyceride level is an independent risk factor for CHD is a controversial. Researchers remain divided with respect to this issue.
Of all the dietary factors studied, fat intake has received the most attention. High intakes of total fat and saturated fat and to a lesser extent, cholesterol, are associated with elevated blood total and LDL cholesterol levels.
Current recommendations state that no more than 30% of energy in the diet should come form fat, no more than 10% of energy from saturated fats and 300mg or less of cholesterol a day.
Conclusion
With respect to dairy products, lower fat dairy products are often recommended. While the fat and cholesterol content of many dairy foods might be expected to increase blood cholesterol levels, there is no scientific evidence that consumption of whole fat dairy foods in moderation within the content of a total diet increases the risk of CHD.
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