HDL is called “good cholesterol” because it’s involved in reverse cholesterol transport or taking excess cholesterol from the arteries back to the liver for disposal. Cholesterol leaves the liver in VLDL particles, which degrade in the blood over time into LDL particles, also referred to as “bad cholesterol.” Some of these LDL particles can get into the artery wall and go rancid (known as oxidation). These modified LDL particles are believed to be the primary causal agent in the clogging of arteries.
The proteins associated with HDL particles have been shown to reduce the oxidative modification of LDL. However, mice fed a high-fat atherogenic diet developed pro-inflammatory HDL particles that do not inhibit the oxidation of LDL. By contrast when these same mice were fed a low-fat, high-fiber diet, their HDL particles prevented the formation of pro-inflammatory, oxidized LDL particles.1 On very low-fat, high-fiber diets, HDL levels sometimes drop but research has shown this does not impair the antioxidant function or the reverse-cholesterol transport function of HDL particles. In fact, such a diet seems to improve both.
Supplements of vitamins C and E, beta-carotene and the mineral selenium have been shown to slow the oxidative modification of LDL particles in test tubes, which has led many to believe they will also protect against atherosclerosis. However, recent studies have found these supplements to be of no real value in preventing heart attacks. A recent year-long study of 153 subjects who took supplements of these antioxidant nutrients and/or cholesterol-lowering drugs may help to explain why. The results of this study found that the heart protective HDL fraction (called HDL2) rose by 42% when the patients took cholesterol-lowering drugs (statins or niacin) but did not budge in those patients who took the antioxidant supplements along with the same drugs.2 The results of this study suggest that taking high doses of antioxidant supplements in combination with cholesterol-lowering medications may impair the functioning of HDL particles. To prevent or reverse clogged arteries, a far more effective approach than antioxidant supplements is a very low-fat, near-vegetarian diet that is high in fiber. Such a diet has been shown to shrink atherosclerotic plaque in most people with advanced coronary artery disease even without cholesterol-lowering drugs.
1. Arterioscler Thromb Vasc Biol 2001;21:481-8
2. Arterioscler Thromb Vasc Biol 2001;21:1320.
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.