GRAND BAHAMA ISLAND -- The word "cholesterol" has probably been in your peripheral awareness for several years. Madison Avenue has certainly helped in that regard. No fools to the profit potential of quick fixes to health problems, advertisers have persuaded many of us to push away the butter in favor of no-cholesterol spreads, and have virtually shamed all decent cows into giving only low-fat milk.

But if you are like most people, the word hasn't seemed more threatening than a distant thunderstorm: not that dangerous unless a lightning bolt hits nearby. Unfortunately, that thinking is wrong. For most of us, walking around with improper levels of cholesterol in our bodies is as dangerous as standing under a large tree, in a puddle of water with metal pole in hand each time a thunderstorm strikes. The key word here is also "improper levels." Cholesterol isn't normally bad. The solid, white, waxy substance is so important to the functioning of our body that it is a part of and also manufactured by virtually all of our cells at one time or other.

Cholesterol, for instance, is the main ingredient in bile. Bile is made in the liver and breaks down fats into smaller pieces so our bodies can absorb them easier. Cholesterol also makes up a good portion of our sex hormones.

When your cells need a little cholesterol to be happy, it is sent to them in the blood. But cholesterol doesn't travel well by itself in the blood stream. Because it won't dissolve in a water-based solution like blood, it would tend to clog up your bloodstream. Your body, being pretty smart, knows this and therefore gets the liver to package cholesterol together with a little fat, which logically enough gives the package "anti-stick" properties. These packages are called lipoproteins.

There are two types of lipoprotein packages: high-density (HDL's) and low-density (LDL's), and both serve very important functions. LDL's take cholesterol to our cells when they need it. HDL's return excess cholesterol to the liver for disposal when the cells are through with it. Normally, our bodies regulate the ratio of these delivery trucks without much problem, making sure the right number is available for each task.

But ... we complicate things when we eat too much animal fat (and saturated vegetable fat). "Too much" varies with some of us, but when we reach that level, things start to go berserk, probably a lot like some drivers on a normally uncrowded street who suddenly find themselves in a traffic jam.

It's at this time, for some reason, that our bodies begin to manufacture even more cholesterol, and for that cholesterol to travel around, it produces more HDL's and particularly more LDL's. LDL's, which take cholesterol to our cells, for some reason seem to be particularly attracted to our arteries. And here is where the problem begins.

When LDL's and HDL's are in balance, cholesterol travels through our arteries with little impact on the health of the arteries themselves, the uncrowded highway we talked about. But when diseases and chemical imbalances in the blood occur (like improper ratios of LDL's to HDL's), the interior lining of the vessels become damaged and these rough points begin to trap LDL's, eventually forming severe traffic jams. Your life-giving blood circulation begins to be blocked. The actual blocked points are called "plaques," and the entire process of damage and plaque formation is called atherosclerosis.

When the blockage happens in the arteries around the heart, you have coronary heart disease: Blood flow decreases to the heart, and eventually the heart muscle itself begins to suffocate. Chest pains are an indication of that suffocation, if you are lucky: For 40 percent of us with heart disease there is no pain to warn us of our blockages. Our first warning is death from heart attack.

Blockages can happen in places other than around our heart. Around the brain they cause strokes or senility. In your legs or arms, in their final progression, they kill tissue, enough at times to necessitate amputation.

Improper cholesterol levels aren't the only things that cause damage in your vascular system. Smoking and high blood pressure and being overweight and at times even heredity factors can bring about damage and put you at high risk for heart disease. But in the case of cholesterol (as with all of these factors except heredity) you don't have to stand there, metaphorically speaking, with your metal pole in the thunderstorm. You can at least ground yourself, even if you won't take the time to walk in from the storm.

Dr. Antonio M. Gotto, an internationally recognized research scientist in lipoprotein research, is president of the International Atherosclerosis Society and a former president of the American Heart Association.

Dr. Gotto's first recommendation is to know your current cholesterol levels, something so obvious it would be silly except for the fact most of us don't know that simple thing. Until very recently, the blood test to determine your level has required laboratory processing, which takes time and $15 to $25 of your money.

You can have the test performed at a clinic, hospital or at your doctor's office, and you should ask for both your HDL and LDL cholesterol levels. Since LDL's turn into the bad guys in the cholesterol world when your body is overloaded on fats, your ratio should be within given limits determined by your age and sex. Your test administrator will tell you your ideal ratio based upon his particular testing protocol.

Determing your HDL/LDL ratio is the ideal thing to do, but new "desk top" testing methods are just coming on the market which tell you the next best thing: your total cholesterol count. These tests require only a finger-prick and give you an instant report. If that count is within your normal range, you're probably okay from a cholesterol risk standpoint; if it's high, you can have further testing for a HDL/LDL ratio.

These units are probably going to be in doctors' offices, at health fairs in schools, at community centers, and probably at shopping mall health fairs real soon. They will not be in shopping malls in the District, however, since health-testing gadgets in general are illegal here.

When you are tested, if your cholesterol levels aren't right, talk with your doctor. Heart disease in particular is a progressive disease, and it responds to better diet, exercise and certain new medications. Until recently, most doctors would tell you these factors would slow heart disease, not reverse it. The very newest research indicates heart disease may be reversed in certain types of cases.

But let's assume your level was reasonably okay. Keep it that way by following Dr. Gotto's second recommendation: If you are over 2 years of age, be aware of the amount of fats you take into your body. For the vast majority of us (let your cholesterol level say if that includes you), we take in too much. For instance, the American Heart Association recommends no more than 30 percent of our caloric intake in fats. If you are average, you take in about 40 percent. That 10 percent, over time, lets loose an awful lot of reckless LDL's to wreak havoc on your health, your pocketbook, and eventually your mortality.

Being conscious of your fat intake before problems begin doesn't hurt as much as you think it will, either. Right now, your changes can be modest. One piece of fried chicken rather than three, or a nice lean cut of meat rather than a fatty burger will do it for most of us. And then try scrambled eggs with half the yolks removed. They'll taste the same but have half the cholesterol. The point is, get in the habit of thinking modification right now. If you don't, your changes later will have to be a lot more dramatic and invariably more unpleasant to your taste buds and happiness.

Now, since I am the original immoderate person, finally on the road to godly living after years of gluttony, I can tell you that the changes are worth it. Modest changes in my eating habits, combined with modest exercise, have continued to lower my cholesterol. Nearly two years ago my total count was 260 with a ratio of 7.2 bad to 1 good cholesterols per deciliter of blood. Three months ago my total count was 201 with a ratio of 4.8 bad ones to one good one. For once in my life, I am walking forward rather than backward.

I hope you will think about doing that, too, and learn your cholesterol numbers as well as you know your blood pressure (you do know that, right?). You may like walking in the rain sometimes, and you may enjoy a thunderstorm from a distance. But I do hope you remember that the thunderclap that makes a storm good and frightening always follows the real danger, the lightning. And should that lightning hit you, you may not be around to hear the thunder.