Excess amounts of cholesterol in the blood can build up on the walls of the arteries, causing plaque to form. This narrows the arteries and can lead to atherosclerosis, or hardening of the arteries. The condition can block blood flow from the vessels to the heart and cause heart disease.
LDL and HDL
Low-density lipoprotein, or LDL, cholesterol can increase in the bloodstream from too much saturated or trans fats in the diet. Sources of saturated fat include meat, poultry and dairy products. Trans fats come from many processed foods. LDL, also called the "bad" cholesterol, builds up on the artery walls, the National Heart, Lung and Blood Institute explains. High-density lipoprotein, or HDL, cholesterol gets rid of excess LDL by carrying it from the bloodstream to the liver. Research suggests that low levels of LDL and high levels of HDL, or "good" cholesterol, reduce the risk of heart disease. Limiting your intake of saturated fats, avoiding trans fats and adding unsaturated fats to your diet might improve cholesterol levels.
Framingham Study
The Framingham Heart Study, begun in 1948 under the direction of the National Heart, Lung and Blood Institute, first identified high blood cholesterol, as well as high blood pressure, obesity, diabetes, physical inactivity and smoking, as a factor involved in heart disease. Some 5,209 men and women in Framingham, Massachusetts, were recruited and given routine exams every two years that included laboratory tests and medical history. The ongoing study has since included second- and third-generation participants from the same families to analyze heart disease risk factors. Researchers found that low cholesterol levels play a role in reducing the risk of heart disease.
Population Differences
Other studies found that American soldiers in the Korean and Vietnam wars had significantly higher levels of atherosclerosis, or hardening of the arteries, than their Asian counterparts, whose diets mainly consisted of rice and vegetables. Rural populations in Asia, Africa and Latin America overall have low cholesterol levels and do not develop heart disease, according to the Physicians Committee for Responsible Medicine and reported in the Aug. 16, 2001 issue of the "American Journal of Cardiology." Other factors, however, also might play a role in cholesterol levels and rates of heart disease in different populations because of cultural differences.
Unsaturated Fats
Monounsaturated and polyunsaturated fats lower harmful LDL cholesterol while raising healthy HDL, the Harvard School of Public Health points out. An analysis of 60 controlled trials by Dutch researchers, reported in the May 2003 issue of the "American Journal of Clinical Nutrition," found that diets that used these unsaturated fats in place of carbohydrates decreased LDL levels and raised protective HDL. Sources of monounsaturated fats include olive, canola and peanut oils; as well as almonds, hazelnuts, pecans, avocados and pumpkin and sesame seeds. Polyunsaturated fats come from sunflower, corn, flaxseed and soybean oils; as well as walnuts, flaxseed and fish with omega-3 fatty acids, such as tuna, salmon, herring, halibut and sardines.
Omega-3
Consumption of omega-3-rich fish might help reduce high cholesterol and high blood pressure, thus decreasing the risk of heart disease. People who follow the Mediterranean-style diet have higher levels of HDL cholesterol, according to the University of Maryland Medical Center. The diet, practiced by populations in the Mediterranean area, includes meals rich in fish, fruit, vegetables and monounsaturated fats, including olive oil. Inuit Eskimos in the Arctic regions tend to have high HDL levels and consume high amounts of fish containing omega-3s.
References
- National Heart Lung and Blood Institute: High Blood Cholesterol
- Framingham Heart Study: History of the Framingham Heart Study
- Physicians Committee for Responsible Medicine: Cholesterol and Heart Disease
- Harvard School of Public Health: Fats and Cholesterol -- Out with the Bad, In with the Good
- University of Maryland Medical Center: Omega-3 Fatty Acids
