heart disease

High Cholesterol: What it Means and What You Can Do About It.

Cholesterol is one of two fats in the bloodstream called lipids. Your liver makes almost all the cholesterol in your blood. Eating high cholesterol low saturated fat foods (such as eggs and shellfish) does not increase your blood cholesterol. The other fat is triglyceride. Almost all triglyceride comes from what we eat or is made in the liver from foods that have a lot of sugar or starchy carbohydrates. Fat does not dissolve in the blood, so these fats are carried in tiny droplets within a protein shell. These proteins are called lipoproteins. Any of these lipoproteins can be elevated without the others, so although many people may say, ”I have high cholesterol,” it is important to know what kind of ”high cholesterol” they have. In this post I will talk about the different kinds of hyperlipidemia (the medical term for high cholesterol), what kind of damage they can do, and how they can be treated both with medicines and diet.

Types of lipoproteins

There are four major classes of lipoproteins: chylomicrons, very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL).

Chylomicrons

Chylomicrons are the largest particles. They carry fat that you eat from the intestine to be used as fuel for the body or stored in fat cells. They are made mostly of triglycerides (90%), which is in the center of the particle with several different kinds of lipoproteins on the outside.

VLDL (very low density lipoproteins)

This is the next smallest class of particles. They contain about 50% triglycerides, 25% cholesterol and the rest a type of fat called phospholipids. They are made in the liver and carry triglycerides and cholesterol to the cells.

LDL (low density lipoproteins)

LDL particles carry more cholesterol than the others. They also deliver cholesterol to the cells. High levels of LDL particles are associated with an increased risk of heart disease. More about this later.

HDL (high density lipoproteins)

HDL particles have the most protein and the least amount of fat contained within them. That makes them more dense, hence the name, high density lipoproteins. The function of HDL particles is to carry cholesterol and triglycerides back from the cells to the liver. This decreases LDL in the cell walls of the arteries and helps prevent heart disease. Low levels of HDL are associated with increased risk of heart disease and high levels with decreased risk of heart disease. Paradoxically, very high levels of HDL actually increase the risk of heart disease.

Cholesterol

Cholesterol is essential to your body. Cell walls are made up of mostly cholesterol. Cholesterol is used to make many essential hormones in the body including estrogen, progesterone, androgen, cortisol and many others. Cholesterol moves in and out of cells to do it’s job. If LDL (and therefore cholesterol) is too high, it can accumulate in the walls of arteries at spots where there is inflammation. More about inflammation later. The immune system sends special cells called macrophages to ”eat” the offending LDL particles, but that causes more inflammation and more accumulation of cholesterol. This cholesterol buildup is called a ”plaque” and these can cause narrowing of the artery and can also cause blood clots to form which can completely block the artery. The result is a heart attack or stroke.

Triglycerides

Triglyceride levels are affected by what we eat. We absorb triglycerides directly from eating saturated fats but the liver also converts any unneeded calories to triglycerides that are then stored in fat cells. Very high triglyceride levels can cause pancreatitis (inflammation of the pancreas). It is likely that high triglycerides also increase the risk of heart disease and stroke, possibly by being deposited in the arterial walls like cholesterol. We are not sure at this point the exact mechanism that connects high triglyceride with cardiovascular disease

Inflammation

Inflammation in the artery walls starts the whole process of cholesterol buildup and plaque formation. In fact, one of the main reasons that statin drugs like atorvastatin (Lipitor) work is that they reduce inflammation in the walls of the arteries as well as lowering LDL (and thus cholesterol). It may well be that inflammation of the artery walls can cause plaque formation to begin even in people with normal LDL levels. We can get some idea how much chronic inflammation is going on in our bodies by having a blood test called high sensitivity C-reactive protein (CRP).

So what causes inflammation of the artery walls and is there anything we can do about it?

Inflammation is increased by our old friends: highly processed foods, sugar, high fructose corn syrup and a diet high in starchy carbohydrates. There is pretty good evidence to suggest that eating large amounts of saturated fats (essentially animal fats) also produces inflammation. Increased belly fat secretes a substance that causes chronic inflammation (See my previous post Why is the United States so fat and what to do about it for instructions about how to measure your belly fat). Finally, inflammation of the gums from plaque on your teeth leads to inflammation in arteries. Of course smoking cigarettes also increases inflammation in your arteries.

You can reduce inflammation in your arteries by stopping smoking if you are a smoker, eating unprocessed foods, especially fresh vegetables, fruits and berries, nuts and fatty fish. Taking good care of your teeth also helps. That means flossing daily and seeing the dentist for cleaning once every 6 months. Regular exercise such as walking at least five times a week also reduces inflammation. If your abdominal circumference is above normal, then losing weight will reduce inflammation. All of these things also tend to reduce LDL and triglycerides too, so you get double duty from these life style behaviors.

When you need to take medicine for hyperlipidemia

A significant portion of high LDL and/or triglycerides is genetic. You can make all the lifestyle changes I talk about above and still have high lipids. If that is the case, then you need to talk to your doctor about starting cholesterol medicine. That will likely be one of the class of drugs called statins. There are quite a few of these and they vary in potency, side effects and drug interactions. Almost everyone will be able to tolerate one of the statins without any significant side effects. There are a few people that have adverse reactions to all of the statins. There are some new non-statin medicines that look promising for decreasing LDL in those few patients who can’t tolerate statins. Your doctor will help you find the right medicine for you to help lower your LDL and/or triglycerides.

Bottom Line

All fats in the blood are carried by special proteins called lipoproteins. Cholesterol is carried mainly by LDL. In the presence of inflammation in the arteries, high levels of LDL lead to plaque formation in the arteries that can eventually lead to heart attack or stroke. High levels of triglycerides also increase the risk of heart disease. Lifestyle changes can reduce both inflammation and number of LDL particles and triglycerides, thus reducing population risk of cardiovascular disease. Sometimes lifestyle changes are not enough and cholesterol lowering medicines are needed.

Heart Disease: What is your risk?

We are inundated with information about what increases or decreases our risk of heart disease. In this post I will talk about what risk really means, how we calculate risk, and some things you can do to reduce risk of heart disease. OK, here we go.

Risk: What does it mean?

Although we often talk about individual risk (or luck, which is the same thing) risk really only applies to populations. We know, for example, that in the population of people buying lottery tickets, one person will win the lottery. We know that for certain, but we have absolutely no way of predicting who that person will be. The millions of other people who buy lottery tickets will not win the lottery. The population chance of winning the lottery ranges from one in 42 million to one in 176 million depending on the lottery. Any individual’s chance of winning the lottery though is either 0% or 100%. You either win it or you don’t. The very low population chance just means that there will be millions and millions more people who don’t win.

The same thing is true for risk of heart disease or any other disease. We can define a population that has a certain risk of heart disease, let’s say 15% over ten years. We can be very sure that 15% of that population will develop heart disease. but 85% of those people will not develop heart disease. For any individual, we have absolutely no way of knowing or predicting whether they will or will not develop heart disease. Individual risk is either 0% (you won’t get heart disease) or 100% (you will get heart disease). Even though a population risk of 15% is considered high risk of heart disease, the vast majority of those people will not get heart disease. Their risk is 0%. If you are one of the 15% who gets heart disease then your risk is 100%.

Doctors and other health professionals talk about individual risk, even though there is really no such thing. They do this to try to get people to change their behavior or to convince them to take a medicine. If you successfully change your behavior in a healthier direction or you take a medicine that you were not taking before, you then belong to a different population that has a lower risk of disease. Even though you belong to a lower risk population, your individual risk is still either 0% or 100%.

Relative Risk Reduction vs Absolute Risk Reduction

When research is done on some medicine or other intervention to see if it works, the medicine or intervention is given to one population and a placebo (inactive medicine) to another very similar population and the results are compared. A common way to report how much the intervention reduces the risk of a particular disease compared to the risk in the control group is to report it as relative risk reduction.

Here is a real world example. Eating a handful of nuts per day reduces your risk of heart disease by 20%. That sounds like a lot for a very simple intervention. The problem is that number does not tell you anything about the baseline risk of the population. What we want to know is 20% of what?

Suppose we have determined by a risk calculator that you belong to a population that has a 15% risk of heart disease over ten years. 20% x 15% = 3%. The absolute risk reduction is 3%. That doesn’t sound quite as impressive, does it? What is really important for you to know about a treatment is how much it reduces the risk compared to the baseline risk of the control population; that is, you want to know the absolute risk reduction for the population of people treated compared to the people who are not treated. Often results are not reported that way and you have to calculate it yourself. More about this later on.

How do we calculate the population risk of heart disease?

There are several heart disease calculators that let you know what heart disease risk population you belong to. Although each of them talk about calculating your individual risk of heart disease over the next ten years, what they really mean is that you belong to a population that has that risk. Remember that there is really no way to calculate risk for an individual. Here is a link to a page from Harvard Health Publishing that lets you try out each of three different risk calculators: Heart Attack Risk Calculators.

How to put yourself in a lower risk population for heart disease

In order to calculate absolute risk reduction of any medicine or change in behavior, you first have to calculate the risk of the population you are currently in. Multiplying the relative risk reduction of any change times your current population risk gives you the absolute risk reduction of that change. The higher your current population risk, the greater the absolute risk reduction of any change. That means that the first thing you have to do is to use one the risk calculators in the link above to calculate your current population risk of getting heart disease in the next ten years.

In the examples below I’m going to assume a moderate ten year population risk of heart disease of 9%. Remember that if you are in a population whose risk is higher than that, the absolute risk reduction of each change will be larger.

Things that don’t involve taking medicine

In this post I’m going to focus on things you can do to reduce your population risk of heart disease that don’t involve taking medicines prescribed by your doctor. Medicines that treat high blood pressure or high cholesterol can also lower your population risk of heart disease. That is a discussion better left to you and your doctor, however.

Exercise

Regular exercise, depending on the amount, decreases 10 year risk of heart disease by 31 to 45%. For a moderate population risk of 9%, that translates to an absolute risk reduction of 2.8% (.09 x .31) to 4% (.09 x .45). To get the higher level of absolute risk reduction you have to exercise moderately for 150 minutes a week and do activities that enhance muscle strength twice a week. Simply being active most of the time as opposed to sitting most of the time puts you in a population that has a significant absolute risk reduction, on the order of 2-3%. Exercise level is included in many of the risk calculators. If your population risk includes exercise then you should not count that separately.

Saturated vs unsaturated fat

Despite what we have all been told over the years, the evidence is pretty weak that eating saturated fat increases your population risk of heart disease. On the other hand, eating more unsaturated fats does decrease your absolute risk of heart disease. Most studies show that people who ate the most polyunsaturated fats (vegetable oils) had about a 25% relative risk reduction for heart disease. Using our 9% population example the absolute risk reduction is about 2% (.09 x .25).

Eating fish

Eating fish twice a week reduces your relative population risk by 16%. Using our 9% population risk example, that translates to an absolute risk reduction of a little over 1% (.09 x .16).

Eating nuts

As I mentioned at the beginning of this post, eating a handful of tree nuts (cashews, pecans, almonds) reduces the relative population risk by about 20%. In our 9% population risk example, the absolute risk reduction is about 2% (.09 x .20).

Increasing dietary fiber

Fiber in the diet can be increased by eating lots of whole fruits, vegetables and whole grains. Observational studies show this causes a population relative risk reduction of 16%. In our 9% population risk example, the absolute risk reduction is a little over 1% (.09 x .16).

Not Smoking

Smoking cigarettes doubles the relative population risk of heart disease. Using our 9% example, the population absolute risk increase is 9% (1 x .09). Conversely, if you quit smoking your absolute population risk would be cut in half.

Putting it all together

If you make all the exercise and diet changes outlined above, they add up. Lets do the math.

9% ten year risk of heart disease -3% for exercise – 2% for eating more polyunsaturated fats – 1% for eating fish twice a week – 2% for eating a handful of nuts per day – 1% for increasing dietary fiber = 0! Obviously no one has zero risk of heart disease over ten years but this calculation makes the point that doing multiple things that reduce your absolute population risk of heart disease by small amounts add up to a large reduction in your population risk of heart disease. Doing all these things puts you in a population that has less than 1% ten year risk of heart disease. Does that mean you won’t get heart disease if you are a member of this population? No it doesn’t. Remember that it is impossible to calculate the risk for an individual. What being in this population does mean is that only a very few people will get heart disease over the next ten years.

Bottom Line

Risk refers to populations, not individuals. Relative risk reductions are reported in the medical literature most of the time because they are larger and look more impressive. Absolute risk reductions are important to know, because they take into account baseline population risks. If you calculate your baseline population risk by using one of the risk calculators, you can easily calculate absolute risk reduction by multiplying the baseline population risk times the relative risk reduction reported in a study or magazine article. Even though one behavior change produces only a small absolute risk reduction, multiple small absolute risk reductions add up to a big absolute risk reduction.