And the interesting parts?

LDL comes in four basic forms: a big, fluffy form known as large LDL, and three increasingly dense forms known as medium, small, and very small LDL. A diet high in saturated fat mainly boosts the numbers of large-LDL particles, while a low-fat diet high in carbohydrates propagates the smaller forms. The big, fluffy particles are largely benign, while the small, dense versions keep lipid-science researchers awake at night.

But here's the problem: The typical LDL test doesn't distinguish between large and small LDL particles ó it can't even spot the difference. And people can have mostly large LDL or mostly small LDL in their overall LDL, depending upon a host of genetic, lifestyle, and environmental factors. Your own personal mix may make all the difference between living to a heart-healthy old age and becoming a Monday-morning casualty at your desk.

But during experiments, Dr. Krauss discovered that while a diet high in saturated fat from dairy products would indeed make your LDL levels rise, "saturated fat intake results in an increase of larger LDL rather than smaller LDL particles," as he wrote in an American Journal of Clinical Nutrition review he co-authored in 2006. A diet heavy in full-fat cheese and butter ó but not overloaded in calories ó triggered the relatively harmless health profile described as pattern A. [...]

Not only is dairy fat unlikely to increase heart-disease risk, Dr. Krauss and others have learned, but reducing saturated fat in a way that increases carbohydrates in a diet can shift a person's LDL profile from safe to dangerous. That's pretty much what happens whenever some well-meaning person with "high LDL" starts eating "low-fat" frozen dinners filled out with corn-derived additives, all the while engaging in the customary ravaging of a basket filled with dinner rolls.