Cholesterol is a bit like sunlight — too much of it can cause problems, but it’s hard to survive without it. A small amount of cholesterol (made by your liver and transported through your bloodstream) is used by your body to create cell tissues and certain hormones, among other functions. This is normal and healthy. But too much blood cholesterol, especially certain kinds, can build up in your arteries, making them more rigid (a condition called atherosclerosis) and eventually blocking blood flow entirely. A blocked artery to the heart can lead to a heart attack. A blocked artery to the brain can lead to a stroke. Both conditions could be fatal.

Whether these blockages occur depends in part on how the cholesterol is transported through your blood — in lipoproteins. Low-density lipoproteins (LDL, “bad” cholesterol) are like local commuter trains that make frequent stops, dropping off cholesterol “passengers” along the walls of your arteries. High-density lipoproteins (HDL, “good” cholesterol) are like one-stop express trains that sweep the cholesterol directly to your liver where it can be processed for removal from your body.

High LDL and low HDL levels put you at a greater risk for heart disease and stroke. That’s why you need to pay attention to each contributing factor to your cholesterol report, not just your total cholesterol reading. Cholesterol is measured in milligrams of cholesterol per deciliter of blood or mg/dL.

How do cholesterol levels get too high? What causes the “bad” cholesterol levels to be too high and “good” HDL levels to be too low? It’s a complex soup of family history and genetics, weight, dietary habits, exercise levels and even how you handle stress.

You can’t get new parents, but you can make small, effective changes in the way you eat and move that can help bring high cholesterol levels under control. Diet is one of the biggest contributors to unhealthy blood cholesterol levels, especially saturated fats (found primarily in animal products such as meat, cheese and milk) and trans fats (found in many processed foods). Some foods, especially eggs, actually contain cholesterol, which can also raise blood cholesterol, but not as significantly as saturated fat does. Other foods and drinks may actually lower “bad” or raise “good” cholesterol. Eating too many carbohydrates can elevate triglyceride levels, which is also associated with lower levels of good cholesterol (HDL). In addition, exercise, including weight training, can improve your cholesterol levels.

If those lifestyle changes don’t bring your levels all down to normal, your doctor may prescribe cholesterol-lowering medications. But lifestyle changes are always at the core of any program to keep your heart healthy.