New Theory about Saturated Fat

We all know that dietary saturated fat is bad because it raises blood cholesterol levels, right?

Well, maybe. 

When we get lipid tests like LDL, HDL, and so forth, they draw blood and then measure these things in the blood. They don't measure them inside the cells, or in the cell membranes. And a new study suggests that high blood cholesterol might simply reflect the membrane's need for cholesterol.

Unsaturated fats make membranes more fluid; saturated fats and cholesterol stiffen membranes. What we need is a balance between the two states, and the body is usually pretty good at knowing what we need.

The new theory suggests that when we eat saturated fats instead of unsaturated fats, the membranes don't need a lot of cholesterol to prevent the membranes from being too fluid, so they don't take the cholesterol out of the blood, and hence blood cholesterol levels are higher.

In other words, blood cholesterol levels can fluctuate according to how much cholesterol is needed in membranes. "The effect of dietary fats on blood cholesterol is not a pathogenic response, but rather a completely normal and even healthy adaptation to changes in diet" says the lead author of the study.

The authors call this the homeoviscous adaptation to dietary lipids model. They note that as of now, this is only a theory that needs to be verified. And they distingish between elevated cholesterol levels from dietary changes and elevated cholesterol levels from metabolic disturbances such as inflammation and insulin resistance.

You can read the abstract of the article here. Unfortunately, the full text is behind a paywall.