News - Nutrition
Introducing complexities. Part two of two
By Daniel Lynch
So then, if bad cholesterol is not about a number, when is cholesterol bad? Well, first of all HDL and LDL are not themselves entirely cholesterol. In addition to cholesterol, they are composed of fats, protein and carbohydrates and many other compounds. Their function is to transport cholesterol and fats through the blood to areas of the body which need it. As you know, fat does not mix with water. Cholesterol doesn’t either. Blood is a watery environment and if just plain fat and cholesterol were put in the blood, you’d have an oil slick.
There are other fat and cholesterol blood transporters aside from HDL and LDL. A few examples are VLDL, IDL and chylomicrons. All of them are structures containing not just fat and cholesterol, but protein and carbohydrates and all function to transport water insoluble substances through your blood. As an entire group they are called lipoproteins. Lipo- for fat, and the protein part surrounds the fat to separate it from the blood, this keeps an ‘oil slick’ from forming; the fat would otherwise all join together. These lipoproteins—LDL, VLDL, IDL, etc.—contain different proportions of cholesterol and fat. So, the reason LDL is often considered bad is because it’s the particular lipoprotein which happens to contain the most cholesterol; its job is primarily to deliver cholesterol throughout your body.
All human science books explain that cholesterol is widely used throughout the body. We use it to produce bile for digesting fats, production of steroids like testosterone and estrogen and for making vitamin D (1). It is therefore critically important that your cells receive a steady supply of cholesterol. LDL is the primary deliverer of it. So LDL or cholesterol are not themselves bad, but there is however some basis for calling them so.
The LDL structure can become damaged, from free radicals; And part of LDL which typically takes the damage, is the fat. This is where diet comes in; some dietary fats are more susceptible to free radical damage and the fats we eat do influence the types of fats throughout our bodies. Dietary fats will influence cell membranes, LDL membranes and any other fat containing part of your body. Basically, the type of fat you eat becomes incorporated into your body. So if we’re eating a lot of easily damaged fats, these ‘weak’ fats become incorporated within us, including within the LDL structure. These are more likely to become damaged within our bodies (2), and one particular result is damaged LDL, also known as oxidized LDL.
When LDL becomes oxidized/damaged, then it’s a problem. Technically, this oxidiation/damage may occur to any lipoprotein, the HDL, chylomicrons, etc. But, remember, it’s the LDL which carries the most cholesterol. So, the immune system responds to this damaged structure floating through your blood by sending macrophages. They engulf the oxidized LDL, but the high cholesterol within LDL cannot be broken down by the macrophage immune cell. The result is a cholesterol-engorged immune cell, called a foam cell, which becomes lodged into the arterial walls.
That is why cholesterol lowering drugs are working in an oversimplified way; they simply work to lower cholesterol as a number. They do not address the true problem: damaged/oxidized fats within LDL and other lipoproteins. Within scientific literature, you will see that that certain dietary fats do corresponse with increased oxidized LDL levels (2). Polyunsaturated oils from corn, soy and cottonseed are common examples. Some fats do not contribute to oxidized LDL. Monounsaturated fats, which egg yolks have a lot of, are one example (2).
Accumulation of damaged LDL in arterial walls is a slow process occurring over many years, and just one meal isn’t going to highly change anything. This study I cited sped up the process of oxidized LDL production. I mention this to avoid scaring everybody into being paranoid about what they eat. But I do think avoiding corn, soy and cottonseed oils and anything that says ‘vegetable shortening’ is worthwhile. I do not use these when cooking at home, avoid buying prepared foods with them on ingredients and, when I go out to eat, try to pick restaurant foods which will not have them in high amounts. So I introduced eggs to you because it’s an easy and practical way to begin using this knowledge.
(1) Champe PC. Harvey RA. Lippencott’s Illustrated Reviews: Biochemistry.
Lippincott Williams & Wilkins; Fourth Edition edition (July 1, 2007).
(2) Bonanome A. Et al. Effect of dietary monounsaturated and polyunsaturated
fatty acids on the susceptibility of plasma low density lipoproteins to oxidative
modification. Journal of the American Heart Association. 1992:12.4;529-533.
