LDL Particle Size

By now, most people recognize the distinction between HDL, the so-called “good cholesterol,” and LDL, “bad cholesterol.” The distinction regarding LDL particle size, however, is just as important, but not universally known. LDL varies by particle size—small and large—and only small particle LDL should be labeled “bad.” Small, dense LDL particles tend to accumulate within the arteries, contributing to arterial plaque.³ Conversely, large, buoyant LDL particles float through the bloodstream and are far less likely to accumulate. Observational studies suggest small-particle LDL predicts heart disease at more than three times the rate of large-particle LDL.⁴

Neither William’s essay nor the response published in The New York Timesmentioned anything about this important distinction between small and large particle LDL. Most healthy individuals have predominantly higher proportions of large-particle LDL and for these people diets lower in carbohydrates and higher in fat have been shown to promote healthier blood cholesterol levels.⁵ Some people, however, are genetically predisposed to a phenotype characterized by a predominance of small-particle LDL and for these people diets lower in fat and higher in carbohydrates may promote healthier blood cholesterol levels.⁶

The Paleo Diet, of course, includes animal foods, some of which contain significant amounts of saturated fat. Dr. Williams stops short of recommending vegan diets for everyone, but readers of his essay might wrongly suppose the Paleo Diet promotes unhealthy blood cholesterol levels and that vegan diets, which are typically lower in saturated fat and higher in carbohydrates, are healthier. This might be true if not for the fact that size does matter regarding LDL—and bigger is better. Research shows that dietary carbohydrates, particularly simple sugars and starches with high glycemic indexes, increase small-particle LDL.⁷ From a cholesterol perspective, these are the foods to avoid. Saturated fat, on the other hand, increases only large-particle LDL, which is benign.⁸

And what about Paleo foods like eggs, which contain higher amounts of dietary cholesterol? Dr. Williams wrote about switching to a “cholesterol-free” vegan diet, implying that dietary cholesterol negatively impacts blood cholesterol. The scientific literature, however, doesn’t support this implication. Clinical studies show dietary cholesterol actually reducessmall-particle LDL and only increases large-particle LDL, the benign variety, while also increasing HDL, thus promoting proper LDL/HDL ratios.⁹Furthermore, according to a recent review, “current epidemiologic data have clearly demonstrated that increasing concentrations of dietary cholesterol are not correlated with increased risk for cardiovascular disease.”sup>10 There’s no reason, therefore, to forgo animal foods. The Paleo Diet naturally promotes healthy blood cholesterol levels.

Read more