Myths and Facts about Cholesterol
High cholesterol is widely recognized as a risk factor for heart disease. What might come as a surprise to many people is that cholesterol is also essential to health — for every cell in the body, and for many of the processes our bodies carry out faithfully and silently each day. Why does the human body need cholesterol to stay in good health?
Cholesterol is vital to human health because every cell membrane in the body, including those in the brain, nerves, muscles, skin, liver, intestines, and heart, is made from it. Furthermore, all of the steroid hormones in your body, including the sex and adrenal hormones, are synthesized from cholesterol.
What processes in the body require cholesterol for normal functioning?
As noted above, cholesterol is essential for the formation and maintenance of cell membranes. It helps regulate the fluidity of the membrane, helps the cell resist temperature changes, and protects and insulates cell nerve fibres.
Cholesterol is also essential for the production of the steroidal sex hormones estrogen and progesterone in women and testosterone in men and the production of the adrenal hormones cortisol and aldosterone. Cortisol is involved in regulating blood sugar levels and in immune and inflammatory responses, and aldosterone is important for retaining salt and water in the body.
In addition, cholesterol is involved in the production of bile salts produced by the liver and stored in the gallbladder. Bile salts help in the digestion and absorption of fat and the fat-soluble vitamins A, D, E, and K.
On the negative side, a low cholesterol level may affect the metabolism of serotonin, a substance involved in the regulation of mood. Furthermore, if your cholesterol is very low you won’t be able to generate sufficient levels of vitamin D from the sun. This problem primarily occurs in those who are malnourished due to chronic disease or famine.
Misconceptions About Healthy Cholesterol Goals
In a healthy person, what are the goal levels of cholesterol in the blood?
Optimal cholesterol — where a person doesn’t develop atherosclerosis (the buildup of plaque that can narrow blood vessels) — is different for every individual. There aren’t precise goal levels that apply to all. Thinking that there are is one of the biggest misconceptions about cholesterol.
Total cholesterol, when considered alone, is a poor predictor of heart disease and heart attack. In fact, studies show that total cholesterol levels among people who’ve had heart attacks are almost the same as those of people who haven’t and that roughly half of the heart attacks occur in people without high cholesterol.
Whether cholesterol gets into your vessel walls depends on many other cardiac risk factors, including high blood pressure, diabetes, obesity, smoking, and yet to be discovered risk factors we can’t yet measure. A person should not be reassured by particular levels of cholesterol, especially if there is a family history of heart disease and other cardiac risk factors.
Far better tests for determining heart attack risk are imaging of the heart’s carotid arteries when a person is young (late teens or early twenties). Then, when men reach 45 and women 55, getting a CT scan of the heart to determine the person’s calcium score. A calcium score is the measure of the amount of calcium in the walls of your coronary arteries. This number reflects the total amount of atherosclerotic plaque that has built up and indicates how all of your risk factors interact with each other to cause heart disease. The higher your calcium score for your age, the greater your risk of a heart attack or stroke.
Do these goals change for a person who has cardiovascular disease or diabetes?
There should be no generic goals. In my practice, I’ve seen diabetics with total cholesterol of less than 200 who still have coronary disease, and then there are those individuals with very high cholesterol who turn out to have squeaky clean arteries. That’s why doctors need to look at each patient individually. Getting a baseline calcium score and then following up every three years is important if your score is initially high. It’s also a way to see if diet, and exercise, and other healthy lifestyle measures, as well as medical therapy (such as statin drugs), are working to reduce risk.
Cholesterol and Diet
Is cholesterol obtained strictly from the diet?
No. The liver makes up to 75 per cent of your cholesterol, most of it at night when you’re sleeping and fasting. Studies show that most cholesterol is synthesized when dietary intake is at its lowest. That’s why it is recommended that people take a short-acting statin, like Pravachol (pravastatin) or Mevacor (lovastatin), at night for those who require medical therapy. Longer-acting statins, such as Lipitor and Crestor, work throughout the day and night. Statin drugs block the enzyme that synthesizes cholesterol in your liver.
Does cholesterol play a role in atherosclerosis and heart disease?
When you look at general populations, the higher the cholesterol the more likely it is to get into the vessel walls and cause blockages. As societies, much higher cholesterol levels in people living in North America than are found in those living in the countryside of China, for example, and we, therefore, see far more heart disease overall in this country than there. In other words, when it comes to individuals living in advanced places like North America, Europe, or South America, your cholesterol level is not a good predictor of heart disease.
As noted above, one individual can have high cholesterol and squeaky clean vessels, while another person may have low cholesterol and advanced atherosclerosis.
What other chronic disease risks are affected by high cholesterol?
In addition to cardiovascular disease and cerebrovascular disease, high cholesterol has been linked to peripheral vascular disease (PAD), which affects the blood vessels outside the heart and brain. In PAD, fatty deposits build up along the artery walls and affect blood circulation, mainly in the arteries leading to the legs and feet. This typically causes intermittent pain, numbness, and/or weakness with exertion.
While high cholesterol does not cause diabetes or high blood pressure, these diseases can affect atherosclerosis. For example, diabetes can lower HDL levels and increase triglycerides and thus accelerate the development of plaque buildup. Because high blood pressure, or hypertension, puts added pressure on the artery walls, over time this extra pressure can damage the arteries. This makes it more likely that cholesterol gets underneath the artery lining and into the wall causing the plaque buildup and consequent narrowing that, in turn, compromises blood flow.
Arthur Agatston, MD: The Truth About Cholesterol