Diabetes has been shown to be a major risk factor in the development of cardiovascular disease (CVD). In fact, people with diabetes are twice as likely to have a heart attack or stroke. What’s more, these outcomes often are seen at an earlier age than in those without diabetes. What is cholesterol, and what role does it play in this process?
Cholesterol is important throughout the body
Cholesterol is a waxy substance in the body present in every cell. It plays an important role in many functions, such as building cell membranes, making bile acids to aid digestion, enabling vitamin D production, and helping the body make hormones. “Being a fatty substance, cholesterol is packaged in a particle called a lipoprotein that transports it through the blood to where it is needed,” says Ronald B. Goldberg, MD, professor of medicine at the University of Miami Miller School of Medicine and senior faculty member of the Diabetes Research Institute. “All cells make cholesterol themselves, but sometimes extra is needed, and it comes from the blood. It is the cholesterol in the blood that causes the cardiovascular problems.”
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Two types of cholesterol
There are two main types of cholesterol that are of interest in heart disease. One is low-density lipoprotein, or LDL, also known as “bad cholesterol.” When there are too many of these particles, they can build up as plaque (deposits of cholesterol, fatty substances, and other materials) inside the blood vessels. This plaque can block blood flow or break off and be transported to the brain or heart, resulting in strokes or heart attacks.
High-density lipoprotein, or HDL, is the “good cholesterol.” HDL plays an important role by absorbing cholesterol and transporting it to the liver, where it can be converted into bile and moved out of the body, helping to lower plaque formation.
Another type of lipid your doctor may evaluate is triglycerides, which are the most common type of fat in the bloodstream. As with LDL cholesterol, high levels of triglycerides are linked to atherosclerosis (the buildup of plaques on the inner walls of the arteries).
Diabetic dyslipidemia increases CVD risk
Some people with diabetes have a condition called “diabetic dyslipidemia,” characterized by low HDL and high triglyceride levels. In this situation, the LDL levels are typically normal, but the particles may be smaller and get into the walls of the arteries more easily.
“Those with diabetes tend to have lower levels of HDL, and part of the risk of CVD in this group relates to this,” says Robert H. Eckel, MD, past president of the American Heart Association and professor of medicine emeritus at the University of Colorado Anschutz Medical Campus in Aurora. “The important message about cholesterol for those with diabetes is that blood cholesterol is probably as much, if not more, related to CVD than in the general population.”
Which is to say, if you have diabetes, keeping close track of your cholesterol takes on even more importance. Diabetes by itself has been shown to damage blood vessels independent of cholesterol levels, and adding high cholesterol to the mix increases the risk. So, while glucose control is an important piece of the puzzle, it is only part of preventing cardiovascular disease.
“The target for both diabetes and CVD is the lining of the blood vessels, and this is where the damage occurs,” says Marc Rendell, MD, medical director of the Rose Salter Medical Research Foundation in Newport Beach, Calif. “It is important to remember that high blood glucose’s effect on blood vessels is independent of the attack of cholesterol. They are two independent factors that contribute to the same results.”
Diabetes type may also play a role
“Generally, type 1 diabetes starts at an earlier age, and CVD tends to be a disease of old age,” says Dr. Goldberg. “The longer you have diabetes, the more damage is done, and the greater your risk for heart disease. After having diabetes for 30 years or more, we see heart disease increase as early as the 40s and 50s.” In type 2 diabetes, there are other processes at work. For instance, weight gain is often characteristic of this condition. Excess weight can lead to insulin resistance, which is associated with reduced HDL, smaller and denser LDL particles, and elevated triglycerides.
When your doctor checks your blood for cholesterol, the results are reported in milligrams of cholesterol per deciliter of blood (mg/dl). Other heart risk factors they will consider include:
- Type of diabetes (e.g., type 2 diabetes may require lower target LDL levels)
- Personal history of cardiovascular disease
- Family history of cardiovascular disease (e.g., having a family member die from a heart attack before 55)
- History of high blood pressure
- Smoking history
Based on your bloodwork results and additional risk factors, your provider will determine the best course of action for keeping your cardiovascular system healthy.
“What we are being taught to do for people between 40 and 75 years old is to keep LDL around 70-100 mg/dl,” said Dr. Goldberg. “If you have other risk factors, the guidelines suggest much lower LDLs.”
Diet and other lifestyle approaches are important
One key approach for managing cholesterol levels is maintaining a healthful diet. Eating foods that contain soluble fiber, such as whole grains, fruits, vegetables, and beans and other legumes, helps to manage cholesterol — this type of fiber binds to cholesterol and prevents it from entering the bloodstream, instead allowing it to be moved out of the body. (Soluble fiber can also help slow the absorption of sugar into the bloodstream, helping to manage blood glucose levels.)
Increasing your intake of “good fats,” including monounsaturated and polyunsaturated fats, is another important step. These fats come primarily from plant and fish sources and are generally liquid at room temperature. Sources that include these types of fat include olive oil, nuts, avocados, flaxseeds, sunflower seeds, and fatty fish such as salmon, mackerel, herring, albacore, tuna, and trout. It’s also important to cut down on saturated fats, which are solid at room temperature and are found in foods such as butter, coconut oil, and animal fats or lard.
Food preparation is another significant consideration. Be sure to eat fewer fried foods, such as French fries, cheese sticks, and chicken strips, and choose to bake, grill, or broil your meat and poultry after trimming excess fat. A registered dietitian (RD) or certified diabetes care and education specialist (CDCES) can provide further suggestions on changes you can make for a heart-healthy and delicious meal plan.
Additional lifestyle approaches that can be helpful include losing excess weight (shedding just 5% to 10% of your body weight can have beneficial effects on your cholesterol levels), getting at least 30 minutes of physical activity five times a week, quitting smoking, and sticking to moderate alcohol consumption (up to one drink per day for women, up to two drinks per day for men) if you drink.
Medications: another important tool
According to Dr. Rendell, “HDL is strongly related to diet. The LDL part is harder to control. While diet can help, most of the low-density lipoprotein level in your blood is determined by genetics. Because of this, lifestyle changes aren’t usually enough by themselves to bring the LDL down to the very low levels needed in diabetes.”
So, along with lifestyle changes, medications may be necessary to manage cholesterol. The most-often used are a class of medicines called statins, which inhibit the production of an enzyme that is needed to make cholesterol in the liver. “The research into statins to lower CVD is incredibly strong,” says Dr. Eckel. “These medications have been shown to lower LDL as much as 60%.”
Statins are generally well tolerated. The most common side effects include muscle pain, digestive issues, and mental fuzziness. Less commonly, problems with the liver, such as elevated liver enzymes, can occur.
For people with certain risk factors, the LDL levels recommended by their doctors may be more than what statins alone can achieve. In these cases, classes of medication that may be used include bile acid resins, which block bile reabsorption in the gut, causing more to be moved out of the body; niacin or nicotinic acids, which work to decrease LDL production in the liver and increase HDL; cholesterol absorption inhibitors, which prevent cholesterol from getting into the bloodstream from the intestine; PCSK9 inhibitors, which increase LDL uptake in the liver; and bempedoic acid, which blocks cholesterol production.
Common classes of cholesterol medications
Bile acid resins (also known as bile acid sequestrants)
- Cholestyramine (brand names Questran, Prevalite)
- Colesevelam (Welchol)
- Colestipol (Colestid)
Cholesterol absorption inhibitor
- Ezetimibe (Zetia)
Citrate lyase inhibitors
- Bempedoic acid (Nexletol)
- Bempedoic acid-ezetimibe (Nexlizet)
Combination calcium channel blocker and statin
- Amlodipine-atorvastatin (Caduet)
Combination cholesterol absorption inhibitor and statin
- Ezetimibe-simvastatin (Vytorin)
- Fenofibrate (Antara, Lipofen, and others)
- Gemfibrozil (Lopid)
- Prescription niacin (Niacor, Niaspan)
Omega-3 fatty acids
Prescription versions include:
- Omega-3-acid ethyl esters: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Lovaza)
- Icosapent ethyl or ethyl ester of eicosapentaenoic acid (EPA) (Vascepa)
- Omega-3 acid ethyl esters (Omacor)
- Evolocumab (Repatha)
- Alirocumab (Praluent)
- Atorvastatin (Lipitor)
- Fluvastatin (Lescol XL)
- Lovastatin (Altoprev)
- Pitavastatin (Livalo)
- Pravastatin (Pravachol)
- Rosuvastatin (Crestor)
- Simvastatin (Zocor)
A two-pronged approach
Even though cholesterol-lowering medications are ultimately necessary for many people with diabetes, focusing on lifestyle measures is an important step for managing your cholesterol — and improving your overall health and well-being. Work with your health care team to determine the best approach for you, and take your cardiovascular health to heart.
Want to learn more about diabetes and cholesterol? Read “Natural Ways to Lower Your Cholesterol,” “Eight Lifestyle Ways to Lower Your LDL Cholesterol,” “Your Cholesterol Questions Answered,” and “Statin Alternatives: Other Medications That Can Lower Cholesterol.”