Archaeologists five thousand years from now, piecing together a picture of our civilization, might well conclude that we were a highly religious culture, all worshipping at the altar of the great god cholesterol, whose name appeared on all of our food containers and who was a constant topic of discussion in books, magazines and newspapers.
Cholesterol may not be worthy of worship, but it is interesting, not least because it’s vital to our well-being. Cholesterol, one of a class of compounds called sterols, is synthesized by our bodies in significant amounts in the liver and intestine, and used as the nucleus of Vitamin D, to build regulatory hormones (including testosterone and estrogen), and to make bile salts. It’s also found in the membranes of all our cells, where its concentration helps determine the membrane’s stability and permeability.
Cholesterol is found throughout the animal kingdom, so when you eat meat and eggs, you eat cholesterol. Nobody worried about this until studies showed that high levels of cholesterol in the blood contributed to artheresclerosis, the build-up of cholesterol-containing deposits along artery walls that can eventually lead to a heart attack or stroke.
We’re so good at synthesizing cholesterol that we don’t need much in our diet–and we’re not so good at getting rid of it. We can’t break it down into its component atoms, and we excrete very little. Normally, the total amount of cholesterol in the bloodstream is kept constant: when the dietary intake of cholesterol is high, liver synthesis is low; when intake is low, synthesis increases. But some people’s bodies can’t cope with high levels of dietary cholesterol, so the concentration of cholesterol in their blood increases. Because of this, people have been urged to cut down on cholesterol intake–and “cholesterol-free” has became a popular marketing phrase.
Unfortunately, a food can boost cholesterol levels in the blood without actually containing cholesterol. Saturated fats, present in lots of cholesterol-free foods, tend to cause a boost in cholesterol synthesis.
Fats consist of chains of carbon atoms with hydrogen atoms attached. In a saturated fat, all the carbon atoms’ available bonds are taken up by hydrogen atoms. In an unsaturated fat, two carbon atoms in the chain are linked by a double bond. In a polyunsaturated fat, there is more than one double bond. These double bonds alter the characteristics of the fat.
In general, saturated fats are solid at room temperature and unsaturated fats are liquid. Animal fats, typically solid, are fifty percent saturated and fifty percent unsaturated; while vegetable fats, typically liquid, are about 85 percent unsaturated.
The current recommendation is that less than 30 percent of calories in the diet (compared to as much as 50 percent in the current “typical” Canadian diet) should come from fat, and no more than 10 percent from saturated fat.
By contrast, people in developing countries get only about 10 percent of their calories from fat, which is probably closer to what our bodies expect. In the Stone Age, after all, fruits and vegetables weren’t “holistic,” they were just “all we’ve got to eat.” This diet was high in fiber–a rather vague term applied to a variety of hard-to-digest substances occurring in some foods. Some types of fiber may interfere with the reabsorption of bile salts, which helps keep cholesterol levels down. However, the main benefit of a high-fiber diet is that high-fiber foods also tend to be low-fat.
In the bloodstream, cholesterol is bound up in complex compounds called lipoproteins. There are two main types of lipoproteins, low-density and high-density. Low-density lipoproteins–“bad cholesterol”–apparently carry cholesterol from the liver to the tissues. High levels of these increase the risk of cardiovascular disease. High-density lipoproteins–“good cholesterol”–apparently carry cholesterol back to the liver, removing it from the bloodstream and reducing the risk of cardiovascular disease.
A high level of cholesterol in the blood is just one of several risk factors for heart disease, but it is a pretty solidly established one, and one that it is possible to do something about (unlike, say, heredity), through eating better and even through drugs which interfere with the body’s ability to synthesize cholesterol. But bowing down at the altar of cholesterol and vowing never to eat another egg, as those far-future archaeologists may well decide was a common religious ritual of ours, is probably extreme.
The ancient Greeks had the right idea: moderation in all things. Moderating your diet is an excellent idea–but do so moderately. You’ll probably live just as long, and you’ll enjoy your life a whole lot more.
