Modern human beings have to struggle with zillions of things everyday. Luckily, our brains have adapted to this messy situation by intentionally ignoring most of them. But one thing never slips out of our minds. Our own health sits on the top of everything else. The revered Chair Mao has spoken it well: “Health is the asset of revolution.”

Last weekend, I bumped into a friend who looked sullen and miserable. He just had a physical checkup. There was nothing wrong about the checkup itself. It was the blood results that bothered him. The results, unfortunately, are not completely normal. His high density lipoprotein (HDL) is lower than normal (less than 40 mg/dL).

In the era of internet, everybody is his own doctor. He quickly ran a google search and only discovered that the isolated low HDL is as dangerous as high LDL. In a sense, his protection mechanism is not well armed. What can he do?

Well, as an informed person (that is, I have studied medicine before but never practiced), I comforted him by pointing out that he should treat it as a good news instead of a toll calling. After all, about a third of American men and 15% of women are on the same boat as he is.

The fuss about lipoproteins started after people could eat as much fat as they wished. As early as the 1960s, high total cholesterol, high LDL, high triglycerides, and low HDL have been established as risk factors for heart attack. Last few decades, we have seen that average LDL level in the whole population has decreased significantly. But this, as G. Rose pointed out in his seminal paper “sick population and sick individuals”, does not mean that the bad lipid profile has a smaller risk of heart attack than before. For many people (such as overweight people), it becomes even more thorny than before.

A little physiology may illuminate the importance of lipids and lipoproteins.

The lipoproteins are the carriers of lipids, shuttling between liver and extrahepatic (out of liver) or peripheral cells. There are very low density lipoproteins (VLDL) which transfer mostly triglycerides (three fatty acids binding together) from liver to other cells. These fatty acids are then either used up (in muscle cells, for example) or stored (in adipose cells such as those around our waists). As a result, the VLDL particles are converted to intermediate density lipoproteins and then to LDL particles. LDL is the main cholesterol carrier in blood. It delivers cholesterol to peripheral cells.

Despite its bad reputation, cholesterol serves very important physiological functions. For example, it is one of the basic elements for cell membrane. Most hormones are derived from cholesterol. The crime cholesterol committed is that it deposits in the blood vessels. In fact, it is the carrier—LDL—that is stuck inside artery walls. There is nothing wrong for LDL to go into artery walls. When everything is all right, it will come out later. But when there are too much cholesterol and LDL carriers in our blood, they enter the artery faster and more than they can return. Inside the artery walls, LDL can be modified, mostly oxidized, and stimulate a cascade of reactions. Macrophages have to take up these LDL (and they essentially die there), thus forming lipid-loaded foam cells. The artery walls become thick and fatty. After that, everything will go wrong in all possible ways.

Therefore, anything which can help remove LDL trapped inside artery walls will be a God’s blessing. Apo-A1, the major apolipoprotein of HDL, is secreted from the liver and can bind lipids quickly in the blood, turning itself into HDL. Therefore, the HDL can remove cholesterol from peripheral tissues, thus reducing the accumulation of LDL in them. Furthermore, HDL can inhibit the oxidation of LDL and other cytokine expressions to lessen the LDL load in cells. These features earn HDL a good reputation.

Where does the HDL ship its cholesterol? Part of them is recycled in the live, and part of them, sadly, is transferred back to VLDL/LDL. All lipoproteins are designed to efficiently work together to use lipids, not to eliminate them. Evolution may have a long way to go to develop some mechanisms to rid unwanted cholesterol.

Therefore, lower HDL indicates a slower removal of cholesterol from extrahepatic cells. It is equivalent to a higher LDL. Some lipid researchers suggest LDL/HDL ratio to represent the magnitude of dislipidemia. A ratio higher than 3 is troublesome.

Anyway, if HDL has such important physiological functions, how can we improve it? Unfortunately, medical science stumbles in this case. There is no drug can treat the low HDL (except niacin related drugs may help a little).

There is still some advice I can give though.

First, get up and do some exercises. It is one of the proven ways to increase your HDL at minimal costs. Regular exercises can not only improve your lipid profile, but also enhance your cardiopulmonary functions. There is no need to address the importance of exercise.

Second, do something about your weight. It is not necessary to lose your weight, as recent evidence suggests that a little extra mass won’t kill you (I have more to say about this in another post). You don’t have to be on any specific diet, but reducing your energy intake while increasing your energy expenditure will make your weight stable, which is much better than weight cycling (The yo-yo weight, weight increases and decreases periodically). Furthermore, reducing fat intake, replacing animal foods with equally nutritious vegetables, and eating less are highly recommended.

Third, start a little drink every once a while. Probably this is the worst advice I can give because of the obnoxious association between alcohol and morality. However, studies have repeatedly shown that a little alcohol drink can prevent heart attack. You have to take that.

Finally, relax yourself. A little bit bad lipid profile is not the end of world. The risk of heart attack from that is much smaller than the risk of car accidents from driving a car. As a matter of fact, almost half of heart attacks occur among healthy people. Furthermore, we have some ways to deal with it.

For every thing, big or small, good or bad, there are some purposes from the almighty God. The unfavorable lipid profile may be his sign to punish your sin. However, don’t worry about your sin (every body has junks in his/her trunk), cleansing yourself right now and you will be reclaimed as his beloved child eventually.