The Hidden Enemy: Cholesterol

Cholesterol is a fat-like substance found in all cells of the body. It is produced in the liver and also obtained from dietary sources. High blood cholesterol levels increase the risk of cardiovascular disease. The higher a person’s cholesterol level is, the greater their likelihood of developing heart disease. In Turkey, cardiovascular disease is the leading cause of death in both men and women. Serum cholesterol levels should be measured in individuals over 20 years of age and rechecked every five years if normal. If possible, triglyceride and HDL-cholesterol levels should also be measured.

Cholesterol is transported from the liver to the cells and back to the liver through the bloodstream. Because cholesterol and other fats are not soluble in blood, they are carried in packets called lipoproteins. The two main types that transport cholesterol are LDL-cholesterol, known as “bad cholesterol,” and HDL-cholesterol, known as “good cholesterol.”

LDL-cholesterol is the primary carrier of cholesterol in the blood. When levels are high, LDL adheres to the inner walls of arteries and forms plaques. These plaques enlarge with the addition of other substances, and clots forming on plaque fissures may block blood vessels. This very common condition is known as atherosclerosis. If blockage occurs in the coronary arteries, it leads to a heart attack; if it occurs in cerebral arteries, it causes a stroke.

A portion of blood cholesterol is carried in packets called HDL-cholesterol. HDL prevents the accumulation of cholesterol in the arteries. Research has shown that individuals with higher HDL-cholesterol levels have a lower incidence of heart disease. Studies by the Turkish Society of Cardiology have demonstrated low HDL-cholesterol levels in the Turkish population. HDL levels below 50 mg/dL in women and below 40 mg/dL in men are considered low.

Cholesterol Categories

Every 10 mg/dL increase in LDL raises heart attack risk by approximately 20%. Conversely, higher HDL levels reduce this risk; each 1 mg/dL increase in HDL lowers cardiovascular disease risk by 2–3%. The higher a person’s cholesterol level, the greater their risk of heart disease. Cardiovascular disease is the leading cause of death in Turkish men and women.

Positive lifestyle changes—reducing fatty foods, preferring liquid oils, avoiding high-calorie foods, exercising regularly, and losing excess weight—can significantly increase HDL and decrease triglycerides. With proper diet and regular exercise, LDL levels may be reduced by 10–15%.

For patients with low HDL, lifestyle modification is essential. Balanced nutrition, physical activity, and quitting smoking have favorable effects on cholesterol levels. While statins—commonly used to treat hypercholesterolemia— increase HDL by only 5–10 mg/dL, quitting smoking increases HDL by 15–20%. Fish oil provides partial improvement in HDL levels.

Triglycerides are the form of fat found in nature. They are both produced by the body and obtained from food. High levels are associated with an increased frequency of heart disease. Although cholesterol has a more prominent link with heart disease, triglycerides are the second most important lipid target.

Triglyceride Levels

• Normal: <150 mg/dL
  
• Borderline High: 150–199 mg/dL
  
• High: 200–499 mg/dL
  
• Very High: ≥500 mg/dL
  

Types of Dietary Fats and Their Effects on Cholesterol
There are three types of dietary fats: saturated fats, monounsaturated fats, and polyunsaturated fats. Solid fats contain more saturated fats, whereas liquid oils contain more unsaturated fats. Saturated fats and dietary cholesterol increase blood cholesterol levels. Saturated fats are highest in animal fats—lamb, beef, full-fat dairy products, and hard margarines. Liquid oils such as sunflower and corn oil contain polyunsaturated fats, while olive oil contains monounsaturated fats.

How Much Fat Should a Healthy Diet Contain?
Daily fat intake should equal 30% of total calories—approximately 55–70 g/day for men and 50–60 g/day for women. Saturated, polyunsaturated, and monounsaturated fats should be consumed in equal proportions. Trans-fat intake should be minimized as part of dietary prevention of cardiovascular disease. Avoiding processed foods containing industrial trans fats is the most effective way to reduce intake to less than 1% of daily energy. Saturated fat intake should be below 10% of total calories—and below 7% in the presence of hypercholesterolemia.

Characteristics of a Heart-Protective Diet

• Overweight individuals should reduce calorie intake and increase physical activity to lose weight.
  
• Visible fat should be trimmed from meats before cooking; organ meat consumption should be limited.
  
• Processed meats (sausage, salami, etc.) should be avoided due to high saturated fat content.
  
• Poultry and fish should be preferred over red meat; grilling, boiling, or steaming should replace frying.
  
• Fish is the healthiest animal protein for the heart. Fish oil supplements should only be taken if prescribed. Shellfish are high in cholesterol.
  
• Grain, vegetable, and fruit consumption should be increased; these foods are low in fat and rich in vitamins and fiber. Soluble fiber reduces cholesterol—found in oats, rye, beans, peas, rice bran, citrus fruits, and strawberries. Insoluble fiber (bran, carrots, radishes, cabbage, cauliflower, fruit peels) does not affect cholesterol but aids bowel function.
  
• Low-fat or skim dairy products should replace full-fat options.
  
• Pastries, cream, and ice cream should be limited due to high saturated fat and egg yolk content.
  
• Egg consumption should not exceed 3–4 per week. One egg contains 213 mg of cholesterol; the daily recommended intake is 300 mg.
  

What Else Can Be Done Besides a Low-Fat Diet?
Smoking must be stopped because it promotes cholesterol deposition in vessel walls and contributes to plaque rupture and vessel occlusion. Smoking also lowers HDL. Increasing physical activity lowers LDL and raises HDL. At least 30 minutes of daily walking reduces heart disease risk. Although moderate alcohol intake raises HDL, its cardioprotective effect is unclear and alcohol has numerous harmful effects; therefore, alcohol consumption is not recommended as a preventive method.

If cholesterol or triglyceride levels cannot be reduced sufficiently with diet and lifestyle changes, medications prescribed by physicians should be used. Most patients who have had a heart attack or stroke use these medications to prevent recurrence.