With September earmarked by the National Heart, Lung & Blood Institute (NHLBI) as National Cholesterol Education Month, now is a good time to better understand the vital and detrimental roles cholesterol plays in health.
What follows is a four-part article which provides an overview of cholesterol along with the dietary and lifestyle recommendations to improve your numbers. The key nutritional supplements that modify cholesterol are also identified. And, the most commonly prescribed medications that reduce “bad” cholesterol and/or increase “good” cholesterol are reviewed.
What is Cholesterol?
With so much information focused on the negative aspects of cholesterol, it’s hard to imagine that this waxy substance is vital to health. Think again.
You may be surprised to learn that cholesterol is the building block of the steroid hormones. Without cholesterol, our bodies would not be able to make estrogen, progesterone and testosterone. The body also manufactures the adrenal corticosteroid hormones such as cortisol from cholesterol.
A number of other key components are derived from cholesterol. Our body synthesizes vitamin D from cholesterol. Bile acids, which are produced by our liver to help us digest fats, oils and fat-soluble vitamins, are derived from cholesterol. Glands in our dermis secrete cholesterol to prevent dry, cracked skin.
One of the most important functions of cholesterol is to maintain cell membrane fluidity. Each of our cells has a lipid membrane which is derived from fats. This membrane must be kept at a constant fluidity. Cholesterol is either removed or added back to the membrane to maintain this consistency.
The type of fats available in the body determines how this membrane is kept in balance. Saturated fats, which are more rigid, encourage cells to remove cholesterol from the cell membrane. Polyunsaturated fats, which are more flexible, encourage cells to add back more cholesterol to the cell membrane. Despite the type of fats provided by the diet, membrane fluidity is held constant simply by adding back or taking away cholesterol. An ingenious system that has health implications.
Cholesterol is transported in the blood by molecules known as lipoproteins. These lipoproteins enable cholesterol to move within the water-based solution of the bloodstream.
Sources of Cholesterol
As the popular Vytorin ad campaign aptly demonstrates, cholesterol comes from two sources – our bodies and the foods we eat.
Cholesterol Production in the Body. Cells are equipped to manufacture cholesterol based on their needs to maintain membrane fluidity. However, other organs in the body including the liver, intestine, adrenal glands and sex glands make cholesterol to perform various functions.
Cholesterol from Foods. Only foods from animal sources contain cholesterol; plant foods are cholesterol-free. Primary sources of cholesterol from foods include eggs, meats and dairy. Eggs and organ meats such as liver contain very high concentrations of cholesterol. The more excess we consume of sugars, saturated, partially-hydrogenated and trans-fats, the more pressure on our body to manufacture cholesterol.
To confuse matters, the daily cholesterol limit of 300 mg was removed from the recently issued 2015 Dietary Guidelines for Americans. This is because increasing evidence shows that dietary cholesterol has very little to do with raising cholesterol levels in your blood. In short, “cholesterol is not a nutrient of concern for overconsumption.”
In the vast majority of people, as the consumption of cholesterol increases, the liver stops manufacturing this substance. However, in about one-third of the population, this mechanism goes awry. As a result, consumption of cholesterol-containing foods must be limited in these individuals.
Cholesterol Removal from the Body
Unlike carbohydrates, proteins and fats, our bodies can’t breakdown cholesterol once it’s been made. As a result, the only way for its removal is through elimination (as bile). The removal of cholesterol is also increased through dietary fiber intake. If fiber is absent, the vast majority of cholesterol is reabsorbed. This explains why vegetarians – who don’t consume as much saturated fat because by they don’t eat meat and whose diet features fruits and vegetables which are high in fiber – have lower blood cholesterol levels.
A deficiency of certain receptors on the liver surface is associated with less rapid removal of LDL or “bad” cholesterol from the blood and high LDL cholesterol levels. This genetic predisposition answers why high cholesterol runs in some families.
Why the Bad Rap?
As with many things in life, too much of a good thing can be bad. This is especially true for cholesterol. Elevated blood cholesterol levels or hyperlipidemia is a major risk factor for cardiovascular disease. Given that heart disease is the number one killer for both men and women, managing cholesterol levels is important.
Excess cholesterol is deposited along the inside walls of arterial vessels. Over time, these fatty deposits or plaques become hardened. This process is called atherosclerosis. As the artery becomes blocked from these deposits, oxygenated blood cannot flow adequately.
Without adequate nutrients in the diet – particularly antioxidants like vitamin C and E – these fatty deposits become oxidized. Recent studies indicate that oxidized cholesterol or oxycholesterol, is even more damaging than non-oxidized cholesterol.
If a plaque ruptures, a blood clot may form on the plaque and block the arteries. Or, these blood clots can travel and block more distant arteries. If an artery to the heart is blocked, the result is a heart attack. If the artery (carotid) leading to the brain is blocked, the result is a stroke.
Knowing Your Numbers
Given that high blood cholesterol levels do not cause any symptoms, the only way to know if you have hyperlipidemia is by getting your numbers checked. The National Institutes of Health recommends that everyone age 20 and older get their cholesterol levels measured every 5 years.
A cholesterol or lipoprotein profile provides the following information (cholesterol levels are measured in milligrams of cholesterol per deciliter (dL) or one tenth of a liter of blood):
Low Density Lipoprotein (LDL) or “bad” cholesterol – transports cholesterol to the tissues. LDL is the main source of cholesterol buildup in the arteries. An LDL level of 130 mg/dL or less is desirable with 100 mg/dL or less as optimal. A level of 160 mg/dL or more is considered high. Lowering LDL levels reduces existing plaques, stops the formation of new plaques and reduces the risk of having a heart attack and stroke.
Lipoprotein (a) Lp(a) – is an LDL cholesterol particle that is attached to a special protein called apo(a). Although largely inherited, elevated levels of Lp(a) (20 mg/dL or more) is a strong risk factor for cardiovascular disease.
High Density Lipoprotein (HDL) or “good” cholesterol – protects against heart disease as HDL cholesterol removes cholesterol from arterial walls and returns the particles back to the liver for disposal as bile. An HDL level of 60 mg/dL or more helps to lower your risk for heart disease. A level under 40 mg/dL is considered low. Very low HDL and very high HDL levels can run in families.
Triglycerides –-a type of fat that circulates in the blood; triglycerides in the blood come from either diet or the liver. A level of 150 mg/dL or less is desirable. A level of 200 mg/dL or more is considered high. Elevated triglyceride levels are associated with conditions that increase the risk of heart disease – obesity, low HDL levels, and diabetes.
Very Low Density Lipoprotein (VLDL) and Intermediate Density Lipoprotein (IDL) – the body synthesizes and packages triglycerides into VLDL particles and releases them back into the blood stream. IDL is formed from the degradation of VLDL.
Total Cholesterol – is the sum of LDL, HDL, VLDL and IDL. A level of 200 mg/dL or less is desirable. A level over 240 mg/dL or more is considered high.
Total Cholesterol/HDL – this ratio is helpful in determining the risk of developing atherosclerosis. The lower the number the better, with 5 or below desirable. Over 6 is considered at risk for developing heart disease.
Knowing your family history is important as elevated cholesterol levels can have a genetic component. In familial hypercholesterolemia, a common inherited disorder, family members have elevated LDL levels and are at greater risk of developing atherosclerosis and heart attacks in early adulthood. High triglyceride levels or hypertriglyceridemia can also be inherited.
Once your cholesterol levels are known, you can determine your heart disease risk using the National Institutes of Health risk calculator. The calculation incorporates sex, age, total cholesterol and HDL level, smoking status, and blood pressure, to determine your risk of having a heart attack in the next 10 years.
If you have high cholesterol, the good news is that with a few modifications in diet and lifestyle, your numbers can improve. For example, a study indicated that for every 1 mg/dL increase in HDL cholesterol, there is a 2 to 4 percent reduction in the risk of heart disease.
To learn more about the foods and supplements which promote healthy cholesterol levels refer to the articles below. Or, refer to High Blood Cholesterol: What You Need to Know, an excellent document written by the NHLBI.
Last updated August 31, 2016