Abnormalities in lipid levels, known as dyslipidemia, are associated with an increased risk for heart disease. High total and LDL cholesterol, high triglycerides and low HDL cholesterol have all been identified as independent risk factors for atherosclerosis, or hardening of the arteries. If you have high cholesterol, your doctor has probably told you to avoid certain foods. If you are already careful about what you eat and your cholesterol level is still elevated, you may be wondering what else to avoid.
Dietary Fats
"The Merck Manual of Diagnosis and Therapy" points out that triglycerides account for more than 95 percent of all dietary fats. Free fatty acids, phospholipids, cholesterol and fat-soluble vitamins making up the remainder. With such a small percentage of cholesterol coming from your diet, you might wonder why your cholesterol level is abnormally high. The answer lies in the way your body produces its own cholesterol.
Cholesterol Synthesis
Your cells need a certain amount of cholesterol to function. Cholesterol is a vital structural element in cell membranes, and it is used to manufacture steroid hormones, vitamins and other important molecules. Under normal circumstances, your body makes about 1,000 mg of cholesterol daily to fulfill its metabolic needs. Cholesterol is synthesized in all of your cells to some degree, but your liver, adrenal glands, intestines and gonads produce larger amounts than other tissues. All of your tissues produce cholesterol the same way, using fatty acids as the raw material.
High-Fat Diet and Cholesterol
A diet that is high in fat, especially one that contains saturated fats, is high in triglycerides. A triglyceride is a special lipid molecule that is composed of a three-carbon backbone hooked to three fatty acid molecules. When your body metabolizes triglycerides, the fatty acids are separated from the backbone and are stored in fat cells, oxidized for energy or shunted into synthetic pathways.
Because triglycerides serve as the substrate for cholesterol synthesis, higher circulating triglyceride levels lead to increased cholesterol synthesis. If you avoid saturated fats, you will reduce the amount of cholesterol produced in your cells. However, if you are genetically inclined to make more cholesterol, your blood level can be high even when you eat a low-fat diet.
High Cholesterol Foods
Although most fatty foods contain cholesterol, some foods contain disproportionately higher levels. Egg yolks, red meat, butter, organ meats, whole milk, aged cheeses and shrimp are fairly high in cholesterol. The American Heart Association recommends that you not consume more than 300 mg of cholesterol daily if your cholesterol is normal, and you should limit daily cholesterol intake to 200 mg if your cholesterol level is already elevated. One large egg contains about 215 mg of cholesterol.
Putting It All Together
Most Americans consume more than 300 mg of cholesterol daily. Removing most of the cholesterol-containing foods from your diet is the first step toward lowering your cholesterol. However, because of the way your body manufactures cholesterol, a more significant impact on your blood level may result from lowering your total fat consumption, with special attention to eliminating saturated, or animal, fats.
References
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Lipid Disorders"; Mark H. Beers, M.D., Editor-In-Chief; 2006
- American Heart Association: Know Your Fats; September 2010
