What causes high blood cholesterol levels?
In Western society, overeating, especially of saturated fats, contributes to high blood cholesterol levels (over 200 mg/dL or 5.2 mmol/L) in most adults. But there are other important causes:
- The body's inability to handle cholesterol properly due to inherited defects in body chemistry. In these situations the levels are usually very high (over 280 mg/dL or 7.5 mmol/L in adults), and usually more than one member of the family is affected.
- Some drugs increase blood cholesterol levels.
- Diseases such as thyroid, kidney and liver disorders; diabetes; as well as several other less common disorders may increase blood cholesterol.
Is a high cholesterol level safe if it is "good" HDL cholesterol?
Yes. Total blood cholesterol is made up mainly of "bad" LDL cholesterol and "good" HDL cholesterol. LDL-C is thought to bring cholesterol to the tissues, and HDL-C is thought to take it away. Therefore, if you have a high level of HDL-C, you are not at risk, and usually have little, if any personal or family history of heart or vascular disease.
Is the ratio of total cholesterol (TC) to HDL cholesterol (HDL-C) useful in assessing risk?
A total cholestererol to HDL cholesterol ratio (TC/HDL-C) greater than 5 is associated with an increased risk of heart attack. However, in those with high triglyceride levels, this ratio may not be valid. As a general rule, however, a TC to HDL-C ratio greater than 5 indicates an increased risk, while a ratio below 4 is associated with reduced risk.
Does the risk of heart disease due to increased blood cholesterol change with age?
Yes. In fact, it may decrease somewhat with age. For example, before the age of 55 a blood cholesterol level greater than 265 mg/dL (6.9 mmol/L) carries a five-fold increase in the risk of heart attack.
However, this increased risk is only 1.7-fold in those over the age of 55. In one study, lowering of blood cholesterol in very old patients with atherosclerosis (average age 75 years) had no effect on the progress of their coronary heart disease. However, it is the lifelong burden of blood cholesterol that matters. Cholesterol levels, on average, decrease in old people.
Does smoking affect blood cholesterol levels?
Smoking slightly increases total cholesterol and triglycerides, but significantly decreases the "good" or HDL cholesterol. This, together with the toxic effects of cigarette smoke, leads to damage of the blood vessels in the heart and legs. In fact, smoking doubles an individual's risk of heart attack at any level of blood cholesterol.
Does exercise affect blood cholesterol and triglycerides?
Yes. Regular exercise increases HDL cholesterol. Also, blood triglycerides (butter-like fats in the blood) decrease, partly because of the decrease in total body fat and increase in muscle mass that usually accompanies exercise. However, exercise alone will not correct high cholesterol levels in most people with inherited disorders of cholesterol, or in those eating a diet high in saturated fats and other dangerous ingredients.
Is it true that alcohol has beneficial effects on the "good" HDL-cholesterol levels?
Moderate drinkers have higher HDL levels than abstainers (or, for that matter, than heavy drinkers whose livers are degenerating). However, alcohol may also cause an increase in blood pressure, which may negate alcohol's beneficial effects in the heavier drinker. It has been suggested that other substances such as flavonoids, phytoestrogens, and polyphenols in red wine also contribute to alcohol's protective properties.
What is the relationship between stress, cholesterol, and heart disease?
A lot has been written about type A versus B personalities and heart disease. Short-term stress does increase blood cholesterol. However, most recent studies show that only angry, hostile personalities are actually at a greater risk of a heart attack. Furthermore, the stress has to interfere with sleep in order to be really harmful.
How soon after my cholesterol decreases does the risk drop?
Interestingly, the changes in blood flow to the heart may be very rapid, probably due to the rapid beneficial effect on the lining of the coronary arteries (the arteries to the heart). However, it takes longer for changes to occur in the cholesterol deposits in the arteries - approximately 2 years. In a study by Dr. Dean Ornish, dramatic lifestyle changes were also found to achieve large decreases in cholesterol levels, with a significant improvement in blood flow through the coronary arteries evident within 12 months. Other studies have also shown very significant improvement within months.
Can atherosclerosis (hardening of the arteries) be reversed, even after a heart attack or bypass surgery?
Yes. Studies have conclusively shown that between 16% and 39% of individuals on cholesterol-lowering regimens had evidence of reversal of the disease and much-improved blood flow through the heart muscle. In a majority of people, the process of atherosclerosis can be stopped or significantly slowed down by lowering blood cholesterol levels. This is due to "stabilization" of the fatty deposits in the wall of the arteries.