| EARLY Trial | UCSF School of Nursing |
| Endothelial Assessment of Risk from Lipids in Youth | University of California, San Francisco |
What is cholesterol?
Cholesterol is a waxy substance that circulates in your bloodstream. Sound like trouble? Not necessarily. Cholesterol actually has an awfully bad reputation for something so critical to good health. Every cell in your body (remember there are 20-30 trillion of them) needs some cholesterol. What's more, many very necessary hormones are made from cholesterol. Cholesterol is so important, in fact, that almost every cell in the body knows how to make it. Your body can make all that it ever needs, and usually this amount can be processed and eventually either recycled into new jobs or cleared from the body without problem.
So how do we end up with too much cholesterol?
Unfortunately, some people cannot clear cholesterol from their body normally and levels build up too high no matter what they eat. They can still, however, make things worse by not eating the "right stuff". Everyone else is capable of raising their cholesterol levels too high just by getting into unhealthy food habits.
Why should I worry about my blood cholesterol?
Too much cholesterol in the blood makes it more likely that your blood vessels will be unhealthy. Unfortunately, the disease of unhealthy blood vessels can sneak up on people, causing lots of trouble without giving any obvious clues or symptoms. Deposits of excess cholesterol can settle little by little into critical places in your blood vessels in a disease process called atherosclerosis. This can continue silently for a long time until one day, enough blood cannot get through anymore and symptoms of heart disease may finally occur. It's important to do whatever you can to keep your heart and blood vessels healthy long before you get to that point.
If some cholesterol is necessary, why does more cause so much trouble?
To explain this, it's important to realize that cholesterol can only travel through blood vessels in packages that make it soluble, that is, packages that make it dissolve in the blood. Otherwise, you would have something like balls of wax in your bloodstream, which would really gum up the system. Cholesterol packages are called lipoproteins and, as the name implies, they are combinations of "lipo" or lipid/fat and protein, with cholesterol tucked inside. The cholesterol packages are classified by their density that largely reflects the proportion of fat to protein. Fat and cholesterol are less dense than protein so higher fat and cholesterol content are seen in the low-density lipoproteins or LDL cholesterol packages. Less fat and cholesterol are found in the high-density lipoproteins or HDL cholesterol packages.
LDL cholesterol which packages about two-thirds of the body's total circulating cholesterol is known as the "bad" cholesterol, because it deposits fat and cholesterol in blood vessels as it moves through them. HDL cholesterol packages on the other hand pick up excess fat and cholesterol from blood vessels and haul it out of the body, thereby earning the name of the "good" cholesterol. In the best of all possible worlds, you don't want your LDL cholesterol to be too high (no more than 110 mg/dL) and you don't want your HDL cholesterol to be too low (no less than 40 mg/dL).
While what you eat can have a big influence on how much cholesterol is in your blood, it may also have important consequences for just how the cholesterol is packaged. This becomes a "quality" not just a "quantity" issue.
How do I improve the quality as well as the quantity of cholesterol?
Scientists believe that if LDL cholesterol packages move freely through your blood stream without irritating blood vessel walls they may not cause as much atherosclerosis. It turns out the LDL can be more or less irritating depending upon just what is included in its package. You remember that LDL packages have lots of fat in them. Fat can be changed in a way that makes it toxic to blood vessels and this change is called oxidation. Fat is oxidized before you eat it by the high temperatures used for deep-frying. Fat can also be oxidized after eating by normal processes inside your body. Either way, oxidized fat within LDL packages makes the LDL more toxic to the blood vessels they must travel through.
Certain kinds of fat are much more likely to get oxidized within LDL. For example, the monounsaturated fat found in olive and canola oil is less likely to get altered in this toxic way. This is why the nutritionists are encouraging those of you participating in the EARLY Trial to avoid deep frying, keep your total fat intake to a minimum, and emphasize monounsaturated fats for those you do eat.
Another good kind of fat to include in your diet is omega-3 polyunsaturated fat. This is the kind of fat found in coldwater fish, flaxseed, soy, and certain nuts, especially walnuts. Omega-3 fats seem to be good not only for the quality of your cholesterol packages, but for your blood vessel cell membranes as well.
Furthermore, it seems that if the LDL package of fat, cholesterol and protein is also loaded up with antioxidant vitamins, it will be better protected from some of the toxic oxidative changes that can cause trouble for your blood vessels. Certainly, the more LDL packages you have in your blood stream all the time, the more likely some of them will be oxidized and therefore will be troublemakers. This is why people try to keep their LDL cholesterol levels down. But at any given level of LDL cholesterol, there are things you can do to minimize the oxidation process. Just how much effect your nutritional efforts are making on LDL oxidation is a big part of what we study in your blood every time we have to take a sample. And the ultrasound pictures we take give us information about whether or not the LDL packages in your bloodstream are bothering your blood vessels. All of the participants of the EARLY Trial are helping us learn a lot more about these important quality/quantity cholesterol questions!
We hope you also are learning important things about how to eat the healthiest way we know. We will be sure to let you know more as we learn more. Meanwhile, remember:
Eat healthy stuff! Move around enough! Live tobacco-free!
Revised: 23 July 2003
© Copyright 2006, 2005, 2004, 2003 University of California Regents, All Rights Reserved.
For more information, contact:
marguerite.engler@nursing.ucsf.edu
Version 1.7 · 17 Jan. 2006