Cholesterol is so important to the body that it makes it itself— Mother Nature doesn’t leave it up to humans to get whatever they need from diet alone. So even if you ate a completely cholesterol-free diet, your body would make the approximately 1,000 mg it needs to function properly.

Your body has the ability to regulate the amount of cholesterol in the blood, producing more when your diet doesn’t provide adequate amounts. The regulation of cholesterol synthesis is an elegant process that is tightly controlled. The system works much as your thermostat and furnace work to regulate the temperature in your home.

The thermostat in this case is a protein that can sense the cholesterol content of a cell. When it senses a low level of cellular cholesterol, the protein signals the genes of the cell (the furnace in this analogy) to produce the proteins that make cholesterol.

The cell makes more cholesterol, and it also makes more proteins on the cell surface that can capture the circulating LDL particles, thereby retrieving cholesterol by bringing it in from the blood. It is this regulation that permits the commonly used cholesterol-lowering drugs to work so effectively.

Almost all of the cells of the body can make the cholesterol they need. The liver, however, is an especially efficient cholesterol factory, efficient enough that it can afford to export much of what it makes. The liver packages much of its cholesterol into lipoproteins that can be delivered to cells throughout the body, providing a supplement to what each cell can make on its own.

This supplement is especially important to the areas of the body that utilize a lot of cholesterol—like the testes in men and the ovaries in women, where the sex hormones are created. In an attempt to make the public health message about keeping your cholesterol at a healthy level easy to understand.

Educators often don’t emphasize the point that all humans make substantial quantities of cholesterol. But it’s important that you understand this because it clears up confusion a lot of my patients voice. When I tell a patient that she has high cholesterol, she may say, “How could that be? I hardly eat any foods with cholesterol. My body must somehow make cholesterol—that’s what’s wrong!”

So I have to explain that making cholesterol isn’t something that she uniquely and unluckily does—all humans do it, and we wouldn’t survive otherwise. Your blood cholesterol level is determined by the sum of how much cholesterol your body makes and how much you take in from food, minus how much your body uses up or excretes.

High cholesterol can result from a problem in any of the variables in that equation—your body may produce more cholesterol than it needs due to a genetic predisposition, you may be getting too much from your diet, or you may not excrete cholesterol in your bile efficiently.

The fact that Americans have higher blood cholesterol levels than citizens of the Far East or Africa could be due to differences in genetic factors, but most evidence suggests that our higher cholesterol levels are largely a product of our high-fat, high-cholesterol diet.

Your body does need food to fuel the cholesterol production process, but it can be virtually any kind of food, even the cholesterol-free kind. As long as the food contains carbon—which carbohydrates, fats, and proteins all do—it provides the body with the building blocks to make its own cholesterol. Cholesterol is made out of the carbon that is recycled from the food you eat.

Saturated fats, however, raise blood cholesterol levels more than other types of food, which is why people watching their cholesterol are told to avoid them. This is true even if saturated fat (which doesn’t have any cholesterol in itself but is often found in foods with high cholesterol) is eaten in a cholesterol-free food. Why saturated fat does this is still something of a biological mystery.