Dr. Robert Kurrle, M.D., Senior AME
Part I: "What is good and what is bad?"
Cholesterol can be both good and bad, so it is important to learn what cholesterol is, how it affects your health, and how you can manage your cholesterol levels. It is also important for pilots to understand the FAA's position on cholesterol and what affects it can have on your flying career.
First, some basic definitions: Lipids are the building blocks of the fatty substances found in plants and animals. They are composed of cholesterol, triglycerides, and lipoproteins. Cholesterol is a fat like substance in our bloodstream that, in small amounts, is essential for cell membranes, some hormones, and other body functions. Cholesterol in high levels causes the buildup of fatty deposits within arteries, reducing or blocking the flow of blood and oxygen. This can lead to heart disease as well as strokes, kidney failure, and poor circulation. We get cholesterol in two ways. The liver makes some of it, and the rest comes from cholesterol in animal products that we eat such as meats, poultry, fish, eggs, butter, cheese and whole milk. Foods from plants such as fruits, vegetables and cereals don't have cholesterol. Some foods that do not contain animal products may contain trans-fatty acids, which cause your body to make cholesterol. Foods that have saturated fats also cause your body to make more cholesterol.
Cholesterol is absorbed from the intestine and processed by the liver. Cholesterol and other fats cannot dissolve in the bloodstream. They have to be transported from the liver by special carriers called lipoproteins. There are two major types of lipoproteins that carry cholesterol: high-density lipoprotein (HDL), and low-density lipoprotein (LDL). Triglycerides are transported separately. When we get a blood test the total cholesterol as well as the HDL, LDL, and triglycerides levels are reported.
HDL is the good cholesterol. You can remember this by thinking of the "H" as "Healthy" and "Higher". HDL may help in reversing cholesterol deposits in the lining of blood vessels. Also, higher levels seem to give some protection from heart disease. You want your "H"DL to be high.
LDL is the bad cholesterol. You can remember this by thinking of the "L" as "Lousy" and "Lower". LDL causes the build up of fatty deposits within your arteries, often referred to arteriosclerosis. The lower the "L"DL, the better.
Triglycerides are the largest portion of lipids in the diet and are a storage medium for energy. Higher triglyceride levels may be associated with a higher risk for heart disease and stroke.
We should all know our lipid levels. Most physicians recommend a blood test to determine baseline cholesterol and triglyceride levels. To provide a proper sample, one should fast (nothing to eat or drink except water) for 12-14 hours before the blood is drawn. Dietary changes in the few days before testing has little effect on cholesterol levels. The American Heart Association has established guidelines for healthy levels of the lipid profile (units are mg/dL):
200 - - - - - - - - - - - - - - - desirable
200-239 - - - - - - - - - - - - borderline high
240 - - - - - - - - - - - - - - - -high
(higher is better)
40 - - - - - - - - - - - - - - - - - low
60 - - - - - - - - - - - - - - - - -optimal
(lower is better)
100 - - - - - - - - - - - - - - -optimal
100-129 - - - - - - - - - - - near optimal
130-159 - - - - - - - - - - - -borderline high
160-189 - - - - - - - - - - - -high
190 - - - - - - - - - - - - - - very high
150- - - - - - - - - - - - - - - -normal
150-190 - - - - - - - - - - - - -borderline high
200-499 - - - - - - - - - - - - -high
500 - - - - - - - - - - - - - - - very high
Some physicians use the ratio of total cholesterol to HDL to access risk, although the American Heart Association recommends the absolute numbers be used. The ratio is obtained by dividing the HDL value into the total cholesterol: Total cholesterol divided by HDL:
less than 5 - - - - - - - - - - - - - - - -good
less than 3.5 - - - - - - - - - - - - - - optimum
You should now have a good understanding of cholesterol, HDL, and LDL, as well as their definitions and healthy levels. Next month we will discuss how we can modify our numbers and what the FAA requires.
CHOLESTEROL, HDL, AND LDL: The good, the bad, and the FAA
Part II "How to modify our levels"
Last month we learned the definition of cholesterol, HDL, LDL, and triglycerides as well as the healthy levels of each. Remember HDL is the "Healthy" component that we want "Higher" – optimal above 40mg/dl. LDL is the "Lousy" component we want lower- ideally below 100mg/dL. Cholesterol is the total amount that ideally should be below 200mg/dl. Lets discuss how we can modify our numbers and what the FAA thinks.
Assuming we know our numbers for cholesterol, HDL, LDL, and triglycerides and where those numbers are in the American Heart Association guidelines for risk, what can we do to modify them? Even if your numbers are good, the following can help to reduce your long-term risk of heart disease:
First, reduce your daily cholesterol intake to less than 200mg with fats making up less than 30% of total calories. Eat fewer foods with high saturated fat levels. This information is on the label of packaged goods where it lists "Nutrition Facts". Diets rich in grains, fruits, and vegetables are ideal. Avoid whole dairy products, rich meats, and saturated fats and oils found in processed foods. Read the nutritional labels on foods – you may be surprised what actually is in them! Good sources of healthy fatty acids include certain fish products (salmon, tuna, trout), and flax seed oil. Adequate dietary intake of certain vitamins including niacin, vitamins E and B, and folate are protective. Increasing fiber intake also lowers cholesterol. Fruits, grains, and vegetables are high in fiber. Diets rich in trans-fatty acids may raise total cholesterol and LDL, and lower HDL. Saturated fats are the biggest cause of increased LDL levels, so avoid foods with a high % of saturated fats (>20%). Buying the right foods to have at home is the first step to healthy eating. The second step is preparing those foods without adding extra fat or salt. Try to trim all visible fat from meat and remove skin from poultry. Grill, bake, or broil meat, use egg substitutes, use margarine or liquid vegetable oils that are highest in unsaturated fats, and increase your consumption of fresh fruits and vegetables. Choose wisely when eating out.
Exercise is a very important step to lowering total cholesterol and raising HDL. Aerobic exercise where the heart rate is raised and maintained for 30 minutes or more is best done several times a week. Consistent aerobic exercises will help raise HDL. If you smoke, stop. Smoking will actually lower your HDL, as well as create numerous other health problems. Reduce weight if you are over weight. Also, reduce any other risk factors you have control over such as blood pressure, your sugar level if you are a diabetic, and stress. These all contribute to your risk of heart disease. There are certain factors you cannot control like heredity, age, or gender. You need to be aware of those factors and minimize all others.
Cholesterol-lowering medications may be prescribed by your physician if your numbers stay at risk, even with diet and life style changes, or if you have certain cardiac risk factors. Several categories of medications are available. The most widely used groups of medications are called the "statins" and include Lipitor, Pravachol, Mevacor, Zocor and Lescol. They are fairly new and have been very effective with few side effects. They are taken once a day. Their major drawback is their cost. Niacin is a B vitamin that works well, but is not tolerated by some people. Bile acid sequestrates like Questran reduce the absorption of dietary fat much like fiber. Some of the earlier triglyceride lowering drugs were folic acid derivatives, but these sometimes caused gallstones. Zetia is a new class of drugs recently approved by the FDA. The FAA approval is not expected until late this year.
FAA reporting requirements are quite simple. First, the FAA does not have any requirements for lipid levels, and in fact, does not request levels except for cardiac evaluation. All of the medications, except Zetia, are approved by the FAA, as long as there are no side effects. They should be reported on your next application for your medical, on line 17, medication. So, know your cholesterol numbers, minimize the risk factors you have control over, eat wisely, and exercise. Happy flying!