re you confused about dietary fats? Well, you're not alone. Judging from the sometimes conflicting reports recently presented at a scientific conference, experts in the field seem to be having the devil's own time sorting out which fats and oils and how much of them are likely to be most beneficial to health and at the same time acceptable to consumers and food producers.
The conference was organized by the American Heart Association, American Cancer Society and Oldways Preservation and Exchange Trust.
Research into the fat issue is unlikely to come to definitive conclusions any time soon. But since you do have to continue to eat, and since fat is part of a normal diet that adds flavor to food, promotes satiation and carries in essential vitamins, you would be wise to follow the advice provided by some of the world's leading experts on the subject.
Dr. Frank Sacks, a cardiac researcher from the Harvard School of Public Health, said it best: "After looking at the whole picture, it makes sense to follow a diet moderate in fat that derives between 30 percent and 35 percent of its calories from fat, but that is low in saturated fat and contains a mixture of natural liquid vegetable oils and fish oil from foods."
There is no perfect fat or oil. As Dr. Sacks noted, "For almost any fat, there will be something not good about it." Although some fats (for example, fish oil and pure vegetable oils) are clearly better for your heart than others (for example, dairy fat, meat fat and hydrogenated vegetable oils), it is not possible to say which of the better oils is best.
Nor is there a hard and fast rule about the amount of fat appropriate in a healthful diet. Looking, for example, at heart-healthy diets in various parts of the world as well as those tested in clinical studies, there is a wide range -- from 10 percent to more than 40 percent of calories from fat -- to be found in wholesome diets.
"No matter what anyone thinks, one size does not fit all," said K. Dun Gifford, founder and president of Oldways, a nonprofit organization that identifies and promotes healthful diets from different countries. "We're driven to find a common denominator -- to simplify, simplify, simplify -- but that's a dangerous thing to do in a culturally diverse society such as ours."
Dr. Sacks made a plea for "the dietary pattern approach that considers foods in the context of the whole diet, not in isolation, since the biological effects of the pattern may differ from the individual effects of component foods."
For example, the Mediterranean diet, which is rich in olive oil yet associated with low rates of heart disease and several common cancers, contains very little meat but is loaded with other health-promoting ingredients, including plentiful vegetables and fruits and dried beans and peas. The traditional Asian diet, on the other hand, is very low in all fats, but also rich in vegetables as well as fish and carbohydrates.
"We've made some mistakes with the low-fat message," Dr. Sacks said. He explained that it led some people to adopt a poor dietary pattern, a diet loaded with calories from refined carbohydrates like white bread, simple carbohydrates like sugar and a slew of convenience foods but with little or no increase in fruits, vegetables or whole grains.
The result has been poor nutrition, widespread weight gain, a precipitous rise in diabetes and little or no benefit to the health of the heart or any other organ.
A study in Lyon, France, may be the best evidence yet for adopting a wholesome dietary pattern.
Participants were men known to have heart disease. Among those who ate more fruits, vegetables, bread, beans, fiber, cheese, poultry, fish and canola oil and less meats, butter and cream, total mortality was reduced by 56 percent, cardiac deaths by 65 percent, nonfatal heart attacks by 70 percent and cancer by 61 percent compared with participants who continued to eat a typical Lyon diet.
Without changing total fat intake for the experimental group, saturated fats in the Lyon diet were replaced by monounsaturated and polyunsaturated vegetable oils and fish oils.
However, Americans have not yet reached the most important goal for fat consumption: a reduction in saturated fats (from meats, poultry, dairy products and solid vegetable fats that are hard at room temperature) to less than 10 percent of calories. Saturated fats, along with trans fats formed when vegetable oil is hydrogenated, raise blood levels of cholesterol and are strongly linked to high rates of heart disease. The average intake of saturates is now at about 12 or 13 percent, and some people are consuming more than 15 percent of their calories as saturated fat.
All fats and oils are mixtures of fatty acids: saturated, monounsaturated and polyunsaturated. And within each of these categories, there are many different fatty acids, each of which has its own pattern of activity in the body.
For example, one kind of saturated fatty acid, stearic acid found in meats and chocolate, does not raise harmful LDL cholesterol levels. Unfortunately, most of the saturated fat in meats is palmitic, which does raise LDL cholesterol and which accounts for about two-thirds of the saturated fat in the American diet.
Another saturated fatty acid, myristic, found in dairy fat, raises LDL cholesterol even more than palmitic, which is a good reason for choosing only nonfat or low-fat dairy foods.
Now let's look at the more healthful fats, the monounsaturated and polyunsaturated oils found in plants and fish. The American Heart Association suggests that up to 15 percent of calories can come from monounsaturates, prominent in olive and canola oils, avocados and many nuts.
Monounsaturates make up an average of 10 percent of calories, with about two-thirds of them coming from animal fats that are rich in undesirable saturated fatty acids. Monounsaturated fatty acids lower harmful LDL cholesterol but have no adverse effect on heart-protective HDL cholesterol, which acts like arterial Drano, helping to keep blood vessels clear of fatty deposits.
According to one conference report, olive oil (but not canola oil) temporarily impairs the ability of blood vessels to dilate, but the health significance of this finding is unknown.
Polyunsaturated fatty acids, prominent in corn, soybean, safflower and sunflower oils, lower blood cholesterol even more than monounsaturates, but they do so by lowering the LDL's and to some extent the HDL's. The heart association suggests that polyunsaturates make up no more than 10 percent of calories, a level above which no population naturally consumes. In studies in animals and tens of thousands of people, diets that favor polyunsaturates lower the rate of heart attacks.
Also helpful are the omega-3 fatty acids, polyunsaturates prominent in fish and a few rarely eaten greens like purslane, as well as canola and soybean oils. Several studies have linked fish-eating to reduced rates of sudden death from heart disease, and the more fish the better. In a study in the Netherlands, the risk of cardiac death was 60 percent lower among frequent fish-eaters than among people who ate little or no fish. However, while fish oil reduces cardiac deaths, it does not prevent cardiac events like heart attacks, suggesting that it works mainly by preventing abnormal heart rhythms rather than atherosclerosis.
(from the New York Times, July 25, 2000, page D8)