Importance of HDL

Dr. Steven Nissen, of the Cleveland Clinic, recently demonstrated that infusing synthetic HDL particles into the blood leads to a more rapid reversal of the plaques in the heart arteries than previously believed possible.1 The man-made protein he used, called “apo A-1 Milano,” differs by just one amino acid from the apo A-1 protein found in a single family in Italy. This Italian family attracted researchers years ago because they:

a) Have very low levels of HDL, or “good cholesterol,” in their blood b) Eat a diet fairly high in saturated fat and cholesterol c) Have LDL, or “bad cholesterol,” levels that are high enough to promote the growth of plaque in their arteries. d) Despite all of these risk factors, these lucky people are resistant to the development of atherosclerotic plaques. Why? Their HDL particles with this unique apo A-1 protein work much faster than normal HDL particles do to get cholesterol out of the arteries and back to the liver. Think of LDL as “garbage” that can accumulate in arteries and ultimately narrow them and cause heart attacks and strokes. HDL particles work like little “garbage collectors” to take excess cholesterol from the arteries and carry it back to the liver where it is disposed. This process is known as “reverse cholesterol transport” because most of the cholesterol in the arteries originates in the liver. In contrast to this family in Italy with unusually low HDL levels, most Americans with a low HDL level show a reduced ability for reverse cholesterol transport. Because low levels of HDL in those eating high-fat diets are usually associated with a greater risk of heart disease, low HDL is viewed correctly as a risk factor for atherosclerotic disease. The National Cholesterol Education Program and the American Heart Association have both warned Americans against following very-low-fat diets, such as those advocated by the Pritikin Program and Dr. Ornish. This is because diets higher in fat raise HDL levels and replacing dietary fat with carbohydrate usually lowers HDL levels, at least in the short-term. However, there is evidence that has shown that in both guinea pigs2 and people3 a switch to a lower-fat diet actually improves the efficiency of HDL particles to return cholesterol to the liver. In both humans and animals, reverse cholesterol transport was not impaired despite a drop of HDL in the blood on a lowfat diet. As has been shown by the Italian family with the Milano apo A-1 protein, a lower HDL-cholesterol level does not necessarily mean increased cholesterol in the arteries. It should be noted that very-low-fat, high-fiber diets generally lower LDL levels much more than they lower HDL. Less “garbage” requires fewer “garbage collectors.”The results of another study done by Nissen4 demonstrated the more LDL levels are lowered, the more likely it is cholesterol deposits in the arteries will shrink over time. A high-fiber, very-low-fat diet is in fact the only dietary approach ever proven to reverse atherosclerosis in humans and other primates.5 Bottom line: When a very-low-fat diet was combined with current drug therapy to modify cardiovascular disease risk factors, heart patients experienced improved blood flow to the heart and cut the risk of having a heart attack more than 300% compared to a more conventional approach.6 Results of this study strongly suggest the best way to unclog arteries and prevent heart attacks for now is to combine cholesterol-lowering medications with a very-low-fat, near-vegetarian diet.

By James Kenney, PhD, RD, LD, FACN. References: 1. JAMA. 2003 Nov 5;290(17):2292-300 2. Woollett LA, Kearney DM, Spady DK. J Lipid Res. 1997;38:2289-302 3. Brinton EA, Eisenberg S, Breslow JL. J Clin Invest. 1990;85:144-51 4. Reported at the November 2003 American Heart Association meeting in Orlando 5. Ornish D, Scherwitz LW, Billings JH, et al. J Am Med Assoc 1998;280:2001-7. 6. Sdringola S, Nakagawa K, Nakagawa Y, et al. J Am Coll Cardiol 2003;41:263-72