The Garbage Trucks in Your Blood

Not everything that lowers HDL is bad for you. If you change from a high-fat, high-cholesterol diet to a healthy low-fat, low-cholesterol diet, your HDL levels may stay the same or even decrease because there is less need for it. When you have less garbage, you need fewer garbage trucks to remove it, so your body may make less HDL. Thus, a reduction in HDL on a low-fat diet is not harmful.

We know this is true because instead of just measuring risk factors like HDL, we measured what actually happens to the progression of coronary heart disease in people who went on diets that were very low in "garbage"—i.e., very low in cholesterol, saturated fat, total fat and refined carbohydrates, and high in fruits, vegetables, whole grains, legumes and soy products.

Their HDL levels came down by 9 percent after one year, but their LDL ("bad") cholesterol levels came down even more, by 40 percent. None of these patients was taking cholesterol-lowering drugs.

Even though their HDL levels decreased, these patients showed reversal of their heart disease using state-of-the-art measures such as quantitative coronary arteriography, cardiac PET scans, thallium scans and radionuclide ventriculography in randomized controlled trials published in the leading peer-reviewed journals. On average, they showed even more reversal of their heart disease after five years than after one year. Also, there were 2.5 times fewer cardiac events such as heart attacks, bypass surgery and angioplasty in these patients.

In summary, a low HDL in the context of a healthy low-fat diet has a very different prognostic significance than a low HDL in someone eating a high-fat, high-cholesterol diet. People living in many Asian countries, where they typically consume a low-fat diet, have low HDL levels yet among the lowest rates of heart disease in the world.

Drugs like torcetrapib raise HDL by slowing its metabolism. This may not be the optimal approach for raising HDL. Other strategies for raising HDL by different mechanisms are being actively explored. Also, torcetrapib increased blood pressure in some patients.