Cholesterol kills.
The renowned Framingham Heart Study found that the risk of heart disease rises 2 percent for every 1 percent that blood cholesterol levels rise above 150 mg/dl. Dr. William Castelli, M.D., medical director of the Framingham study, says they have not found one heart attack among study group participants whose cholesterol levels are below 150. Cholesterol is a Jekyll and Hyde substance.
Arterial blockages by cholesterol kill about half a million people each year, yet cholesterol is in the membranes of every cell. Cholesterol serves as the electrical insulation of nerve cells; the body uses it to make a number of hormones and the crucial Vitamin D.
Cholesterol is so important to your body that your liver can manufacture all you need without you eating even a single gram of it. This is where the problem begins. On its own, the liver will use saturated fats to make the cholesterol it needs. Conversely, the liver filters out the excess cholesterol and excretes it as bile salts. Those salts pass through the gall bladder into the intestinal system where their detergent-like action helps digest other fats and cholesterol. (The cholesterol may not be gone forever since the bile salts are largely reabsorbed from the intestine into the body.)
Cholesterol is like thousands of other beneficial compounds, ranging from aspirin and alcohol to Vitamin A and Zinc. If your body gets too much, the high concentrations overwhelm the biochemical mechanisms for dealing with it. Suddenly your lifestyle has laid a potentially fatal trap for you.
Scientists think that excess cholesterol is caused by:
People have differing abilities to cope with cholesterol. About five percent of the population has levels that remain high despite low intake of cholesterol and fats.
Most people with elevated cholesterol levels consume too much cholesterol and saturated fat. In addition, these diets are apt to lack fruit, vegetables and other sources of soluble fiber that lower cholesterol levels.
Studies show that stress tends to raise the overall cholesterol level, with proportionately larger increases for "bad" LDL cholesterol than for "good" HDL.
Moderate exercise can raise your HDL levels and help lower overall cholesterol levels. It is not clear whether the lower level is due directly to the exercise or to its stress-reducing effect.
Obviously, this book can't do anything about your genetic make-up. If you're the 1-in-20 person whose cholesterol level is genetically unable to respond to lifestyle changes, you need to see your physician to discuss other options such as drug therapy. But for the rest of the population, diet, stress reduction and exercise can all help save your life.
Cholesterol is a waxy chemical with a complex molecular ring structure that, by itself, is insoluble in blood.
Because of this insolubility, cholesterol needs a blood-soluble compound to transport it through the body. The suitable vehicle is another molecule called lipoprotein. This is a disk-shaped molecule with a fat (lipo) portion, that attaches to the cholesterol, and a protein portion that surrounds the cholesterol and makes the whole package soluble in your water-based blood. In one sense, the cholesterol molecule rides inside the lipoprotein like an astronaut in a hockey-puck-shaped space capsule.
Lipoproteins are a vital part of the cholesterol equation. You've seen the reference to "good" HDL and "bad" LDL cholesterol. Well, you've been tricked, in a small way, for the sake of explaining a complex biochemical situation. Cholesterol is the same molecule regardless of whether it's riding in an HDL or an LDL capsule. But how the lipoprotein capsule operates determines whether the cholesterol is "good" or "bad".
Blood lipoproteins are very specialized. LDL carries cholesterol from the liver to the body's cells; HDL carries excess cholesterol from the cells to the liver.
When an LDL gets to a cell that needs cholesterol, it unloads its cholesterol molecule. When all your cells have enough cholesterol, it's another story. The LDL particles circulate continuously through the blood where a finite number of them bind wit LDL receptors, primarily in the liver. Binding with an LDL receptor removes the cholesterol from the blood. Genetic variations in the number of LDL receptors may account for our ability to handle cholesterol.
When the LDL receptors are saturated, the LDLs circulate through the blood and, through a complicated series of biochemical steps, eventually end up dumping their cholesterol loads in your arteries. Atherosclerosis begins.
High LDL levels work against you in another way. Research has shown that high LDL levels actually decrease the number of LDL receptors, thus making a bad situation worse. Saturated fats are another double whammy. They decrease LDL receptor activity and increase LDL levels. When things go wrong, they can go wrong big time.
On the other hand, HDL circulates through the blood like a taxi cruising for a cholesterol fare to take back to the liver, which converts it to bile salts. More HDL circulating means more cholesterol gets scavenged from your system and returned to the liver for a safe exit.
Scientists still don't know if HDL is the prime mover in cholesterol removal or if some other hidden factor actually prompts the HDL to perform its job. Like so many other things, we know that high concentrations of HDLs are associated with a decreased risk of heart disease and we know how HDLs perform this service. Science just doesn't know yet why it works. When we know the why we may begin to understand how moderate alcohol consumption and other factors increase HDLs.
Today, science does know that lowering overall cholesterol is important to decreasing heart attack risk. Further, it's important to have as high a proportion of HDL as possible.
Dr. Meir Stampfer of Harvard Medical School found in a 1988 study that a 1-point increase in HDL produced about a 7 percent reduction in heart attack risk.
People who measure only their total cholesterol are missing a crucial part of their health equation. A good overall target for which to aim is 150 but the ratio of total cholesterol to HDL is equally important.
The Framingham study indicates that a ratio of 5:1 (total cholesterol:HDL) puts men at an "average" risk of heart attack; 4:1 for women. This ratio would be found in someone with a total cholesterol level of 180 in which LDL measured 150 and HDL, 30.
While 180 is significantly below the 200 level for which most people strive, another person with the same total cholesterol level would be at higher risk if the HDL measured only 15 -- a ratio of 11:1.
As you can see, raising or lowering the HDL level can dramatically alter the ratio. A ratio of 3:1 cuts your risk to less than half of the average; your risk doubles at 9.5:1. People with ratios of more than 23:1 triple their heart attack risk.
Like cholesterol, fats (triglycerides) are substances your body can't do without, but which can kill you if you eat too much. Sustained high blood concentrations of fat, hyperlipidemia, are suspected of being one of the factors that damage artery walls and promote atherosclerosis.
But fats are also necessary for cell growth, for the body's synthesis of needed chemicals and for energy. During sustained exercise, free fatty acids provide 40 to 60 percent of the affected muscle's energy. The longer the exercise, the more the muscles rely on fatty acids. In fact, your longest-exercising muscle -- the heart -- relies almost exclusively on free fatty acids (FFAs) for its energy.
Like cholesterol, fats are not soluble in your water-based blood; they need specialized transport vehicles to get them from one place in your body to another. Those transport vehicles are also lipoproteins. Both VLDL (very low density lipoprotein) and chylomicrons deal with triglyceride transport.
VLDLs contain some cholesterol but primarily transport triglycerides to adipose tissue for storage as fat. VLDL can be converted into LDL; in a blood test it is counted as part of the LDLs.
Chylomicrons primarily move fat from the intestine to the liver. From there it is either converted to VLDLs for transportation to love handles and double chins or stored as fat in the liver itself.
Chylomicrons are processed rapidly and are mostly gone within 9 to 15 hours after you eat the mealtime fats that prompted their formation. Blood for triglyceride tests is usually drawn first thing in the morning before you have had anything to eat (and nothing since dinner the evening before -- a 12- to 15-hour fasting interval). That's so the VLDL triglyceride levels will not have been altered by chylomicron concentrations.
Like most people, you may be confused by the apparently inconsistent use of the words: fat, oil, fatty adds, triglycerides. The differences and similarities are easy to understand. Fats and oils are both triglycerides; the only difference is that at room temperature fats tend to be solids and oils tend to be liquids. For most non-technical purposes, fat, oil and triglyceride can be used interchangeably.
Triglycerides are molecules composed of three (thus the "tri") fatty acids bound to a glycerol (thus the "glyceride") molecule.
(To confuse the layperson even more, an international scientific nomenclature commission has ruled that the word triacylglycerol is more scientifically correct than triglyceride. You may start seeing this new word in magazines and newspapers.)
The glycerol (also known as glycerin) is identical in all triglycerides (fats). But what makes a fat "good" or "bad" for your health depends on which three fatty acids are hooked up to it.
The bad fatty acids are those which have the maximum number of hydrogen atoms attached to them -- they are "saturated". Saturated fats tend to raise your cholesterol level.
Conversely, fatty acids whose molecules do not have all the hydrogen possible are known as "unsaturated". Monounsaturated fats contain molecules that are only one hydrogen short of saturation while polyunsaturated fatty acids lack two or more
hydrogen atoms.
Polyunsaturated fats are better than saturated for decreasing heart disease risk, but some studies have indicated that a diet high in polyunsaturated fats may increase the risk of cancer and also lower HDL levels. Monounsaturated fats (like olive and canola oils) are most effective at increasing good HDLs and do not have an associated increase in cancer risk.
A glycerol can have two or three different kinds of fatty acids hooked up to it or they can all be the same. In fact, fats and oils are all mixtures of saturated, mono- and polyunsaturated fatty acids. Olive oil, for instance, is known as "heart healthy" because it contains more monounsaturated fatty acids (77 percent) than any other dietary oils. But even olive oil contains saturated fatty acids (14 percent) and polyunsaturated fatty acids (9 percent). By contrast, beef fat is 50 percent saturated fatty acid, 42 percent monounsaturated and 4 percent polyunsaturated. But the kings of saturation are tropical oils. Coconut oil is 86 percent saturated and palm kernel, 81 percent.
Food technologists, however, are rarely content with the foods that nature has provided; oils are no exception. Food manufacturers will often put unsaturated vegetable oils through a chemical process known as "hydrogenation" that adds hydrogen to the fat molecule. While this increases shelf life and changes the texture of the resulting fat or oil, it also robs the formerly unsaturated oil of some of its health benefits. Margarine and all-vegetable lard are two examples of partially hydrogenated vegetable oils. These were among the earliest techno-foods.
There was much to-do several years ago about the cardio-protective nature of oils from salmon and other cold-water fish. Those oils contain a high concentration of omega-3 polyunsaturated fatty acids.
Lab research suggests that omega-3 fatty acids don't seem to affect cholesterol levels. In fact, participants in one lab study who ate about 1 tablespoon of fish oil per day actually increased their LDLs. These types of fish oils, however do seem to help prevent atherosclerosis by decreasing the tendency of white blood cells called monocytes to stick to artery walls. However, little more is known, including whether you get the same protective effect by taking pill supplements containing omega-3 fatty acids. Eating lots of salmon is more fun, but grill it or use olive oil in the preparation; butter only ruins the health effect. And don't bother with fish oil capsules. Just eat lots of fish instead. The New England Journal of Medicine has reported that men who daily ate an average of 30 grams (slightly more than one ounce) of fish rich in omega-3 fatty acids cut their heart attack risk in half -- that's just 7 ounces per week.
Cholesterol is measured in milligrams per deciliter of blood (abbreviated mg/dl). A deciliter is one-tenth of a liter and a liter is slightly smaller than a quart. A milligram is one- thousandth of a gram and there are 454 grams in a pound. When people refer to their cholesterol as "225" or "178" they are referring to mg/dl.