Nutrition: Fats Chapter 5

Two Sources of Cholesterol: You Eat It & You Make It


From Food To Cells: How Fats and Cholesterol Move

The Good, The Bad and The Greasy

We know that dietary fats are essential. But before your body can put these fats to use, they must somehow get from your digestive system into your cells. This isn’t as simple as it sounds, explains Harvard researcher Walter Willett, in Eat, Drink, And Be Healthy, The Harvard Medical School Guide to Healthy Eating. Fats and blood, like oil and water, do not mix. “If your intestines or liver simply dumped digested fats into your blood, they would congeal into unusable globs.” READ MORE

The body gets around this basic chemistry problem, writes Willett, by packaging fat and cholesterol into “protein-covered particles that mix easily with blood and flow with it.” The cholesterol helps to stabilize the particles, and the size and density of the lipoprotein (from the Greek lipos, for fat) determines whether its cholesterol is classified as “good” or “bad.” High-density lipoproteins (HDL), also known as “good” cholesterol, are small, dense, protein-rich lipoproteins; low-density lipoproteins (LDL) are larger, lighter, and fluffier lipoproteins.

The protein component in these packages does more than just allow them to easily travel through the bloodstream. “They also act like address labels that help the body route fat-filled particles to specific destinations,” explains Willett, who likens the bloodstream to a highway at rush hour, carrying “many sizes and shapes of fat-transporting particles.” The ultimate purpose of all this activity is to get fats and cholesterol to cells and tissues that need these vital nutrients. LESS


What’s bad about “bad” cholesterol?

LDL is referred to as bad cholesterol because it is LDL particles that form the plaque deposits that can clog arteries. What researchers believe is taking place is that when too many LDL particles are circulating in the bloodstream, they accumulate in the lining of blood vessels. Once there, they are vulnerable to reactions with molecular debris called free radicals and these reactions (oxidation) can, in turn, trigger inflammation and further response by immune cells. The oxidized LDL particles accumulate like a rust spot that grows until it eventually constricts or blocks flow through a pipe. READ MORE

What complicates this even further is that not all LDL particles are identical; they differ in shape, size and density. Some researchers believe that the smaller, denser LDL particles are more easily oxidized by free radicals and therefore pose a significantly higher risk of heart disease.

Dietary Cholesterol

The role of cholesterol as a risk factor for heart disease is understood more clearly today, but questions still remain. It is difficult, for example, to untangle the genetic elements from the dietary elements. For some people, eating foods rich in cholesterol has only a modest effect on their blood cholesterol levels, says Dr. David Katz. But for other people, however, blood cholesterol levels rise and fall very sharply depending on how much cholesterol those individuals are getting through their diet.

Why the difference? The underlying reasons appear to be genetic. People who respond strongly to dietary cholesterol are called “hyper-responders.” Increase the cholesterol in their diet and their blood levels go through the roof. For other people, however, eating more cholesterol-rich foods will make only a small difference to their blood levels. Unfortunately, explains Katz, at this point there’s no reliable way, other than trial-and-error, to predict who will be a hyper-responder.

Saturated fats also get in on the cholesterol act. If a person’s diet is high in saturated fats, blood levels of cholesterol seem to be more strongly affected by dietary cholesterol. The combination of high cholesterol and saturated fats makes a bad situation even worse. And indeed, studies have shown that cholesterol, saturated fat and the risk of heart disease generally all rise (or fall) together.

Food File: Scrambled, Fried or Poached Cholesterol?

The egg in the American diet has ridden something of a dietary roller coaster. It’s been called “the perfect food” and been advertised as “incredible, edible.” But it has also become the poster food of cholesterol. Average egg consumption per person in this country has plummeted over the past 50 years, from more than 400 to less than 250. And yes, an egg has more than 200 mg of cholesterol. But eggs are also relatively low in saturated fats. Researchers have somewhat mixed data on the impact of egg consumption. For healthy individuals, the evidence suggests that eating an egg a day doesn’t increase the risk of cardiovascular disease or stroke, although eating more than 7 eggs per week does, especially for people who already have type 2 diabetes. LESS


Managing Cholesterol with Dietary Change

The sensible approach to dietary cholesterol, is to, well, be sensible. Cholesterol is unavoidable in diets that include animal protein, including dairy. Eliminating it entirely, then, requires a strict vegan diet. That, in turn, requires very careful planning to ensure that a person is getting enough protein and micronutrients. It’s not impossible, but it can be very difficult. What is certainly possible (and highly recommended), however, is to eat less saturated fat and cholesterol while maintaining a nutritionally complete diet.

Roughing It: The Cholesterol & Fiber Connection

Another piece of the dietary puzzle is the role of soluble fiber on cholesterol levels. There are 2 types of fiber: soluble and insoluble. Both types are found in fruits and vegetables and both are good for you. But there is an important chemical difference. Insoluble fiber is plant material that is insoluble in water; it’s basically indigestible roughage. It adds bulk to the stool and speeds digestion. Soluble fiber, on the other hand, is at least partially soluble in water. And while it too is basically indigestible, it turns into a gel-like substance in the gastrointestinal tract and is partially fermented by microbes. Soluble fiber tends to slow digestion. READ MORE

Soluble fiber also lowers levels of blood cholesterol, which lowers the risk of cardiovascular disease, by soaking up bile (which is made from cholesterol) and disposing of it. Soluble fiber also helps regulate blood sugar levels, which reduces the risk of type 2 diabetes.

The American Heart Association recommends getting about 25 grams of fiber a day (this figure includes both soluble and insoluble fiber). Foods high in soluble fiber include oat bran, oatmeal, beans, peas, lentils, nuts, rice bran, barley, citrus fruits, strawberries, apples, blueberries, pears, citrus fruit, Brussels sprouts and psyllium seeds (the ingredient in many fiber supplements). Foods high in insoluble fiber include wheat bran, barley, carrots, celery, tomatoes, brown rice, vegetables, and whole grains. LESS


More Food For Thought, Including Dessert

Chocolate has long been equated with indulgence. Lately, however, it’s gotten a reputation as health food. Many studies have shown that there are biologically active components in chocolate that seem to the lower serum cholesterol, reduce inflammation, and arterial plaque. READ MORE

Not just any chocolate, however. The glamorous new health food is dark chocolate, the bitter sibling of the sugary, milk chocolate with which most people are familiar. In fact, acknowledges Katz, some of the research into dark chocolate’s health powers used preparations of chocolate that weren’t commercially available. This is changing, however, as the popularity of dark chocolate grows.

The beneficial effects of chocolate have been attributed to compounds known as flavonoids (which belong to a larger class of compounds called polyphenols) that possess powerful antioxidant properties. Wine and tea also contain these compounds, which are widely in many fruits, vegetables and cereal grains, but in less concentrated quantities.

Chocolate can’t be treated as a major food group, of course. There are lots of calories in chocolate, however, thanks not just to the sugar that is used to enhance its flavor, but also to fat. In solid dark chocolate, nearly 80% of the fat is saturated. There is growing evidence, however, that the saturated fat in chocolate, stearic acid, doesn’t deserve the bad name of the rest of the saturated fat family (more about that later). LESS


Also Joining the Dietary Cholesterol Mop Brigade

There is growing research into a wide range of foods that, like soluble fiber, can lower serum cholesterol. Research into compounds called sterols and stanols have resulted in the National Cholesterol Education Program recommending the compounds for people with high cholesterol. And in 2000, the Food and Drug Administration first authorized a health claim on the basis of evidence that such compounds reduced the risk for coronary heart disease. READ MORE

Plant sterols and stanols are naturally found in small amounts naturally in grains, vegetables, fruits, legumes, nuts, seeds and oils. It’s difficult to get enough of the compounds in whole foods. That’s where fortified foods may help, which is why plant sterols are being added to foods such as margarine, juices and cereal bars. LESS

The material on this site is for informational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any medical condition. Consult a licensed medical professional for the diagnosis and treatment of all medical conditions and before starting a new diet or exercise program. If you have a medical emergency, call 911 immediately.