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LDL may not have the same impact on cardiovascular risk when you’re eating low-carb.

Analogy #1 – Boats in Your Bloodstream

"Low-density-lipoprotein" (LDL) is like a boat that transports two types of cargo through the bloodstream. LDL transports cholesterol (an essential cellular building block for cell membranes and hormones) and triglycerides (fat fuel) from the liver to organs around the body that need building blocks and fuel.

LDL Levels Can Increase for Two Reasons

If you’re eating a low-carb diet and burning fat as fuel, your liver sends out more LDL boats to supply fat fuel to your muscles. The empty LDL boats return to the liver to dock, restock, and go back to work. Alternatively, when you overeat carbs, it is as if you’re filling your bloodstream with sugar glaciers. The LDL boats bump into these sugar glaciers and get damaged in a process classed glycation. (Glycation, in turn, makes those LDL boats further vulnerable to another damaging chemical process called oxidation.) Once damaged by the sugar glaciers, the LDL boats can’t return to the liver and end accumulating in your bloodstream. Eventually, they shrink down and sink down to your artery walls and develop atherosclerotic plaques, a titanic health catastrophe.

Therefore, the perception that LDL is "bad" is not entirely true. More LDL may be needed when you’re burning lots of fat fuel. In fact, the kind of big fluffy LDL that sometimes increases on a low-carb diet is actually cardioprotective! ( 1, 2, 3) By contrast, LDL is bad when it gets damaged by carbs and oxidation, causing it to sink and leading to heart disease ( 1, 2, 4, 5).

Then, there is "high-density lipoprotein" (HDL). Often called "good" cholesterol (although neither LDL nor HDL are themselves cholesterol), HDL is like a rescue submarine that salvages cargo from sinking LDL, cleaning up your bloodstream and protecting against heart disease ( 6).