Separating Fat From Fiction
Bradley A. Radwaner, M.D., F.A.C.C.
The amount and nature of fat in the American diet has long been a matter of public debate. As early as 1977, the U.S. Senate Committee on Nutrition and Human Health recommended that Americans limit their fat consumption to 30 percent of total daily calories, made up of 10 percent saturated fat, 10 percent unsaturated fat and 10 percent cholesterol. These early guidelines are close to what most dietitians and cardiologists would recommend today; yet, at the time, they sparked enough controversy to cause the government, in a 1980 revision, to eliminate all specific percentages. Over the past 25 years, researchers have confirmed that blood cholesterol is an important risk factor for heart disease and have clarified the effect of various dietary fats on blood cholesterol. In addition, some research has implicated a high-fat diet as a possible factor in the development of some forms of cancer, and there is no question that fat is more calorie-dense than other foods and, as a result, contributes to weight problems. Even though the average American still gets about 45 percent of his or her calories from fat, increasing n umbers are becoming aware of the health hazards and would like to reduce the amount of fat in their diets. As the food industry responds with products marketed as "non-cholesterol", "low-fat," or "light", many consumers have become understandably confused about the complex role of various fats in a healthy diet.
CHOLESTEROL: NOT THE FATTEST CAT
Cholesterol, the fat with the greatest name recognition, is technically not a fat all but a fat-related compound that has an ability to combine with fatty acids. Cholesterol is found in every animal cell (lean as well as fat meat),…but never in fruits, vegetables or any plant derivatives -even peanut butter or vegetable oil. Egg yolks and organ meats such as liver and kidney are particularly rich in cholesterol. Cholesterol is a primary ingredient of the crust-like plaque that forms in the walls of arteries, eventually obstructing the flow of blood and leading to a heart attack. Cardiologists now feel there is no safe level of cholesterol above 180 mg/dL of blood, and every one percent increase in blood cholesterol results in a two percent increase in the risk of a heart attack. The human body is capable of manufacturing all the cholesterol it needs so there's no danger in eliminating all dietary cholesterol…although there's no reason to do so. The American Heart Association now recommends a daily intake of about 300 milligrams of cholesterol a day - a little more than that found in one egg yolk. The relationship between blood cholesterol and dietary cholesterol is, however, not as direct or simple as many believe. A person's serum cholesterol level is determined by many factors, including heredity, age and sex. Obesity, caused by excess calories of any kind, can also cause high blood cholesterol. Even considering dietary factors alone, cholesterol is not as crucial as total saturated fats - whether the source be animal or vegetable. As a result, eliminating all foods containing cholesterol will not assure either a low-fat nor a heart-healthy diet.
SATURATED VERSUS UNSATURATED
All fat-containing foods are made up of a variety of fatty acids classified according to their chemical structure as either saturated or unsaturated. Generally speaking, a saturated fat is solid at room temperature; an unsaturated one is liquid. Foods high in saturated fatty acids include meat fat, lard, butter, milk, cheese, ice cream and the oils most commonly used in commercial baked cookies, cakes and doughnuts - cocoa fat, coconut oil, palm oil and palm kernel oil. Because saturated fats are less likely to turn rancid, they are also useful in processed foods that must sit on the shelf for extended periods. Foods containing more unsaturated than saturated fatty acids include fish, the white meat of poultry, nuts, grains and most liquid vegetable oils. Through a process called hydrogenation, a liquid unsaturated oil can be made more solid and usable as a spreadable margarine. The process also makes the fat more saturated.
Another important distinction is between polyunsaturated (safflower, sunflower, soybean) and mono-unsaturated (olive, avocado, canola, walnut and peanut) oils. Whereas saturated fats increase blood cholesterol, unsaturated ones tend to decrease it or at least displace some of the saturated fats. In comparison, mono-unsaturates reduce only the LDL, thereby tending to increase the ratio of "good cholesterol". Trying to improve your blood cholesterol profile by over-dosing on olive oil is, of course, not recommended. All food contains a mixture of fats in varying proportions; along with mono-unsaturated fatty acids, you'll also be getting an unhealthy dose of saturated fats and calories. The gain in weight from too much or any oil will greatly increase the cholesterol. With understanding of the differences between saturated, polyunsaturated and mono-unsaturated fats, it is possible to make sensible use of the information available on food labels. As far as your heart is concerned, saturated fats are worst, followed by cholesterol. Mono-unsaturates are probably preferred over polyunsaturates. Some studies have suggested that omega-3 fatty acids (found in fatty fish and marketed widely in fish oil capsules) may offer some protection from heart disease. As for cancer and other disorders, the formula is similar. A diet high in fat has been associated with a higher risk of breast and colon cancer. And all fats are culprits when it comes to weight control. Fat has nine calories per gram compared to four per gram for protein and carbohydrate.
LEAVE THE FAT
For Americans, the safest approach is basically what the U.S. Senate Committee recommended, then rescinded, 25 years ago. Fat is an essential nutrient and source of energy that cannot and should not be eliminated completely, but affluent Americans eat far more than is necessary or prudent. In China, where the diet is traditionally low fat, blood cholesterol levels typically range from 90 to 180, heart disease is rare and life expectancy exceeds 70 years. That is until the Chinese immigrate to America, adopt the American high fat diet and then develop the same degree of heart disease. Keeping total fat under 30 percent can be accomplished with a little vigilance. While most Americans know the danger of making a steady diet of steak, shake and fries, they tend to overlook the less obvious sources of fat: the blue cheese dressing that smothers the green salad, the buttery croissant that cradles the tuna, the four teaspoons of saturated fat use to make the oat bran muffins. Whether a food has cholesterol is less important that the percentage of calories derived from fat and whether that fat is saturated, polyunsaturated or mono-unsaturated. When looking at food labels make sure that the percentage of calories from fat is less than 1/3 of the total calories. That is the official legal definition of "low-fat" and these are the food to be favored.