Sunday, September 28, 2008

Cholesterol Confusion

Everyone knows what cholesterol is now - that stuff that clogs arteries and causes heart attacks, right?


When you get a blood test for "cholesterol", what they are measuring is not the chemical cholesterol directly, but instead is the total amount of certain lipoproteins that just happen to contain some cholesterol. It's a bit of a misnomer - sort of like calling a car an engine. Let's measure the weight of all those engines on the road by totaling the weight of all the cars on the road. What's worse, there are many other vehicles on the road that have engines but are not cars, like trucks and buses. Does it make sense to total the weight of just cars as an indication of the weight of engines on the road?

There is a chemical called cholesterol and it's an essential part of every cell membrane. It's a precursor to several important hormones and to vitamin D. It's considered both a sterol and a lipid, but not a fat. All fats are lipids, but not all lipids are fats. Cholesterol and fats are not soluble in water, but are needed by our cells. In order to transport cholesterol and fats through our blood, which is largely water, our body bundles them into packages of protein, fat,and cholesterol that can be carried in the blood. These packages are lipoproteins.

There are several kinds of lipoproteins the body uses for different purposes. They are classified by their density, which also roughly corresponds to their size. The largest and least dense are chylomicrons, followed by very low density lipoprotein (VLDL). Both of these contain cholesterol but are not included in total "cholesterol" blood tests. Next are low density lipoproteins (LDL), intermediate density lipoproteins (IDL), and high density lipoproteins (HDL).

In blood tests, the VLDL is called "triglycerides", even though all lipoproteins contain triglycerides (more confusion?) and "total cholesterol" is the total of LDL, some IDL, and HDL.

So how do cholesterol and lipoproteins relate to heart disease?

True cholesterol does not really appear to be a player in heart disease. It is actually very important for good health. However, glycated proteins and fats as well as oxidized fats, all of which can be incorporated into lipoproteins, do appear to play a role. Glycation occurs when a sugar molecule, such as fructose or glucose, binds to a protein or fat and oxidized fats are generally polyunsaturated fats that have been oxidized into peroxides. Some types of glycated proteins and all fat peroxides can cause a variety of problems and are implicated in both heart disease and cancer.

For optimal health, and thus avoidance of heart disease and cancer, we should be striving to reduce our load of glycated proteins and oxidized fats. Elevated blood sugar and triglyceride levels are correlated with elevated blood levels of glycated protein. So, obviously, keeping blood sugar and triglyceride levels normalized is ideal. Eat starches with fat and protein to minimize blood sugar spikes after meals or snacks. Don't eat foods with added refined sugar and don't eat too much fruit. Low-carb diets and/or excercise tend to normalize blood sugar and triglycerides.
The fats most prone to oxidation are polyunsaturated fats. Large amounts of dietary polyunsaturated fat are new to the human diet. Up until the last couple hundred years, the typical amount of dietary polyunsaturated fat was around five percent of dietary calories or less. Only recently has the amount of polyunsaturated fat been increasing dramatically in the human diet as cheap vegetable oils have displaced healthier animal fats in commercial food products. Keeping dietary polyunsaturated fats under four percent of total calories is ideal. That means avoiding most processed foods like sauces, dressings, baked goods, and most cooking oils, and eating only small amounts of nuts. Most commercial sauces and dressings are loaded with soybean oil or other oils high in polyunsaturated fat. Most commercial cooking oils are also high in polyunsaturated fat and sometimes trans-fat (made from hydrogenated polyunsaturated fat). That means avoid most commercial fried and baked foods.


Marc said...

That is one fantastic post!!!

Very nice way of explaining.
Thank you.

Have a great day.

Bryan - oz4caster said...

Thanks Marc! It took me many years to get over my cholesterol confusion :)