What are HDLs?

High-density lipoproteins (HDL) form a class of lipoproteins that carry fatty acids and cholesterol from the body’s tissues to the liver. About thirty percent of blood cholesterol is carried by HDL.[1]

It is hypothesised that HDL can remove cholesterol from atheroma within arteries and transport it back to the liver for excretion or re-utilization—which is the main reason why HDL-bound cholesterol is sometimes called “good cholesterol”, or HDL-C. A high level of HDL-C seems to protect against cardiovascular diseases, and low HDL cholesterol levels (less than 40 mg/dL) increase the risk for heart disease.[1] When measuring cholesterol, any contained in HDL particles is considered as protection to the body’s cardiovascular health, in contrast to “bad” LDL cholesterol.

Epidemiological studies have shown that high concentrations of HDL (over 60 mg/dL) have protective value against cardiovascular diseases such as ischemic stroke and myocardial infarction. Low concentrations of HDL (below 40 mg/dL for men, below 50 mg/dL for women) are a positive risk factor for these atherosclerotic diseases.

Data from the landmark Framingham Heart Study showed that for a given level of LDL, the risk of heart disease increases 10-fold as the HDL varies from high to low. Conversely, for a fixed level of HDL, the risk increases 3-fold as LDL varies from low to high.

Level mg/dL	Level mmol/L	Interpretation
<40	<1.03	Low HDL cholesterol, heightened risk for heart disease, <50 is the value for women
40–59	1.03–1.52	Medium HDL level
>60	>1.55	High HDL level, optimal condition considered protective against heart disease

More sophisticated laboratory methods measure not just the total HDL but also the range of HDL particles, e.g. “lipoprotein subclass analysis”, typically divided into several groups by size, instead of just the total HDL concentration as listed above. The largest groups (most functional) of HDL particles have the most protective effects. The groups of smallest particles reflect HDL particles which are not actively transporting cholesterol, thus not protective.

Source: Wikipedia, January 28, 2008

This entry was posted on Sunday, August 10th, 2008 at 4:39 am by sanguan and is filed under General, Nutrition. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.