Why is HDL the good cholesterol?
HDL is the good cholesterol because it protects the arteries from the atherosclerosis process. HDL cholesterol extracts cholesterol particles from the artery walls and transports them to the liver to be disposed through the bile. It also interferes with the accumulation of LDL cholesterol particles in the artery walls.
The risk of Atherosclerosis and Heart Attacks in both men and is strongly related to HDL cholesterol levels. Low levels of HDL cholesterol are linked to a higher risk, whereas high HDL cholesterol levels are associated with a lower risk.
Very low and very high HDL cholesterol levels can run in families. Families with low HDL cholesterol levels have a higher incidence of Heart Attacks than the general population, while families with high HDL cholesterol levels tend to live longer with a lower frequency of heart attacks.
Like LDL cholesterol, life style factors and other conditions influence HDL cholesterol levels. HDL cholesterol levels are lower in persons who smoke cigarettes, eat a lot of sweets, are overweight and inactive, and in patients with type II diabetes mellitus.
HDL cholesterol is higher in people who are lean, exercise regularly, and do not smoke cigarettes. Estrogen increases a person’s HDL cholesterol, which explains why women generally have higher HDL levels than men do.
For individuals with low HDL cholesterol levels, a high total or LDL cholesterol blood level further increases the incidence of Atherosclerosis and heart attacks. Therefore, the combination of high levels of total and LDL cholesterol with low levels of HDL cholesterol is undesirable whereas the combination of low levels of total and LDL cholesterol and high levels of HDL cholesterol is favorable.
What are LDL/HDL and total/HDL ratios?
The total cholesterol to HDL cholesterol ratio (total chol/HDL) is a number that is helpful in estimating the risk of developing Atherosclerosis. The number is obtained by dividing total cholesterol by HDL cholesterol. (High ratios indicate a higher risk of Heart Attacks, whereas low ratios indicate a lower risk).
High total cholesterol and low HDL cholesterol increases the ratio and is undesirable. Conversely, high HDL cholesterol and low total cholesterol lowers the ratio and is desirable. An average ratio would be about 4.5. Ideally, one should strive for ratios of 2 or 3 (less than 4).
What are the treatment guidelines for low HDL cholesterol?
In clinical trials involving lowering LDL cholesterol, scientists also studied the effect of HDL cholesterol on atherosclerosis and Heart Attack rates. They found that even small increases in HDL cholesterol could reduce the frequency of Heart Attacks. For each 1 mg/dl increase in HDL cholesterol, there is a 2 to 4% reduction in the risk of coronary heart disease. Although there are no formal NCEP (please see discussion above) target treatment levels of HDL cholesterol, an HDL level of <40 mg/dl is considered undesirable and measures should be taken to increase it.
How can levels of HDL cholesterol be raised?
The first step in increasing HDL cholesterol levels (and decreasing LDL/HDL ratios) is therapeutic life style changes. When these modifications are insufficient, medications are used. In prescribing medications or medication combinations, doctors have to take into account medication side effects as well as the presence or absence of other abnormalities in cholesterol profiles.
Regular aerobic exercise, loss of excess weight (fat), and cessation of smoking cigarettes will increase HDL cholesterol levels. Regular alcohol consumption (such as one drink a day) will also raise HDL cholesterol. Because of other adverse health consequences of excessive alcohol consumption, alcohol is not recommended as a standard treatment for low HDL cholesterol.
Medications that are effective in increasing HDL cholesterol include Nicotinic Acid (niacin), gemfibrozil (Lopid), estrogen, and to a much lesser extent, the statin drugs. A newer medicine, fenofibrate (Tricor) has shown much promise in selectively increasing HDL levels and reducing serum triglycerides.
Revision date: July 4, 2011
Last revised: by Sebastian Scheller, MD, ScD