Can Total Cholesterol Levels Be Too Low?

There's so much talk about the dangers of high cholesterol, but are low cholesterol levels equally bad? Healthy cholesterol levels seem to follow one of life's major rules: Avoid extremes.

Cholesterol levels can fall within one of three ranges. For adults, normal cholesterol levels are between 140 and 200 milligrams per deciliter (mg/dL). Total cholesterol levels above 240 mg/dL are considered high, and levels below 140 mg/dL are considered unusually low, although many perfectly healthy people have levels in this range.

High total cholesterol levels are bad -- that is a no-brainer. Too much of this wax-like, fatty substance in the blood can lead to artery disease (atherosclerosis), heart disease, or stroke.

But compared to high cholesterol, low cholesterol is pretty much off most people's radars. While there is no question about the value of reducing high cholesterol as a strategy for preventing or treating heart disease, there is much less agreement on how (or whether) to respond to very low cholesterol levels.

There is agreement on what low values mean for these two components of cholesterol.

• A low LDL cholesterol is desirable. A value of less than 100 mg/dL is the best.
• A low HDL cholesterol is bad, as it protects against heart disease. A level less than 40mg/dL is a warning sign, showing an increased risk of heart disease. It's preferred to have a level of 60 mg/dL or more.

From the standpoint of heart health, the total cholesterol level can't be too low. But unusually low levels of HDL could undermine the body in other areas, including the brain, liver, and digestive system.

There is a chicken-or-the-egg aspect to this problem. Which comes first, low cholesterol or a disease that causes low cholesterol levels? Scientists are still researching this. One disorder where the patient suffers from low HDL is Tangier Disease or familial alpha lipoprotein deficiency.

Low cholesterol can provide benefits in one area and do harm in another. For example, over a long period, very low cholesterol levels increase the odds of hemorrhagic stroke which occurs when a blood vessel ruptures and bleeds into the brain. Such strokes are more likely in individuals with low cholesterol levels because blood with small amounts of cholesterol does not clot as easily. However, an ischemic stroke (which is far more prevalent) occurs when clots or other material blocks blood flow to the brain, and cholesterol is a major source of such blockages.

Cholesterol also plays a role in brain function. It appears that insufficient brain cholesterol hinders the action of serotonin, a chemical that carries messages between brain cells and that is closely associated with mood. Abnormally low cholesterol levels have been linked to depression and anxiety.

For other conditions, low cholesterol is more of a symptom than a cause. The liver produces about three-quarters of our body's cholesterol supply, with the remaining supply coming from diet, especially from meat, eggs, dairy, and seafood. Not surprisingly, cholesterol levels can drop if the liver is compromised due to alcoholism, cancer, or another disease. Any serious disease of the gastrointestinal tract or malnutrition can also reduce cholesterol levels.

Cholesterol is essential to the body and is present in every cell. Without it, sex hormones would not be produced and food digestion could not take place.

The best plan of action is to keep total cholesterol within the middle range, somewhere between 150 and 200 mg/dL. Since high cholesterol is far more common than low, the best way to keep cholesterol levels within the normal range is to maintain healthy lifestyle choices: Eat plenty of fruits, vegetables, whole-grain bread, and nuts; limit whole-fat foods, processed flours, and sugars; and get plenty of exercise.