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Carbohydrates and LDL

Posted Apr 04 2010 7:33am
There's a curious and powerful relationship between carbohydrates and LDL particles. Understanding this relationship is crucial to gaining control over heart disease risk.

(Note that I did not say "LDL cholesterol"--This is what confuses people, the notion that cholesterol is used as a surrogate marker to quantify various lipoproteins, including low-density lipoproteins, LDL. I'm NOT interested in the cholesterol; I'm interested in the behavior of the low-density lipoprotein particle. There's a difference.)

1) Increase triglycerides and very low-density lipoprotein particles (VLDL)
2) Triglyceride-rich VLDL interact with LDL particles, making them smaller. (A process mediated by several enzymes, such as cholesteryl-ester transfer protein.)
3) Smaller LDL particles are more oxidizable--Oxidized LDL particles are the sort that are taken up by inflammatory white blood cells residing in the artery wall and atherosclerotic plaque.
4) Smaller LDL particles are more glycatable-- Glycation of LDL is an important phenomenon that makes the LDL particle more atherogenic (plaque-causing). Glycated LDLs are not recognized by the LDL receptor, causing them to persist in the bloodstream longer than non-glcyated LDL. Glycated LDL is therefore taken up by inflammatory white blood cells in plaque.

Of course, carbohydrates also make you fat, further fueling the fire of this sequence.

The key is to break this chain: Cut out the carbohydrates. Cut carbohydrates and VLDL and triglycerides drop (dramatically), VLDL are unavailable to transform large LDL into small LDL, small LDL is no longer available to become oxidized and glycated, blood sugar is reduced to allow less glycation. Voila: Less atherosclerotic plaque growth.

Yet the USDA, American Heart Association, and the Surgeon General's office all advise you to eat more carbohydrates. The American Diabetes Association tells you to eat 70 grams or so carbohydrates per meal. (Yes: Diabetes, the condition that is MOST susceptible to these carbohydrate effects.) Follow their advice and you gain weight; triglycerides and VLDL go up; calculated (Friedewald) LDL may or may not go up, but true measured LDL (NMR LDL particle number or apoprotein B) goes way up; small LDL is triggered . . . You know the rest.

The dance between carbohydrates and LDL particles requires the participation of both. Allow one partner to drop out of the dance and LDL particles will sit this dance out.

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