BETTY ANN BOWSER: For more than a generation Americans have been told they can reduce their risk of heart attack and other diseases if they exercise, don't smoke cigarettes, and reduce the amount of fat in their diets.
SPOKESPERSON: We're also doing a grilled salmon today. It's marinated, served over pablano rice.
BETTY ANN BOWSER: Over the years Americans have reduced their average fat intake from about 40 percent 15 years ago to about 33 percent of their total daily diet today. Throughout the years of the low fat message from medical science millions of Americans have been eating margarine instead of butter because they thought it was healthier. They've lined up at the salad bars and ladled on the low fat dressing. Even the fast food industry got on the low fat bandwagon by cooking French fries in vegetable oil, instead of beef tallow. Now, a Harvard University study of more than 80,000 nurses suggests it's not how much fat you eat that's bad for you, it's the kind of fat you consume. Researchers studied the eating habits of the nurses for 14 years. Nine hundred and thirty-nine of them had heart attacks or died from heart disease. And the biggest culprit was a fat called partially hydrogenated oil, or trans fat. It's a vegetable oil that has been processed into solid form. Trans fat is found most prominently in stick margarine and in packaged foods like donuts, cookies, and many snack foods, and yes, even in French fries in fast food restaurants.
SPOKESMAN: Fried chicken became a staple in most homes because it was very cheap.
BETTY ANN BOWSER: Not only did the study suggest that trans fat is bad for you, it showed that the chance of having a heart attack increased 53 percent for the nurses who hate more of it. The research also suggested that trans fat may be a more powerful indicator in heart attacks than smoking cigarettes. The study also confirmed once again what had been previously known about saturated fats found in meat and dairy products; that too much of them in the diet is not good either.
MARGARET WARNER: To help put this latest research in perspective we're joined by a co-author of the study, Dr. Walter Willett, chairman of the Department of Nutrition at Harvard's School of Public Health, and by Barbara Howard, a nutritionist and president of the Research Institute of Washington Hospital Center. She is also a member of the American Heart Association's Nutrition Committee. Dr. Willett, is that the most important finding of the study; that it really isn't how much fat you eat, it is the type of fat?
DR. WALTER WILLETT, Harvard School of Public Health: That's right. And we did find that trans fat from partially hydrogenated vegetable oil seemed to be the worst type of fat. The good news was that substituting unsaturated fats, such as from liquid vegetable oils, for either trans fat or saturated fat, can very substantially reduce the risk of heart disease. But on the other hand, substituting carbohydrates for the good fats can actually increase the risk of heart disease.
MARGARET WARNER: All right. Let's go back to these good fats and bad fats because you actually divided it into four categories. And if you could explain those sort of briefly and simply, on a sliding scale, start at the worst, or start at the best.
DR. WALTER WILLETT: Right. The worst type of fat on an ounce for ounce basis seems to be trans fat in the diet from partially hydrogenated vegetable oils. Then comes saturated fat. Mono unsaturated fat actually looks to be somewhat good compared to carbohydrates.
MARGARET WARNER: I'm sorry. Let me dial you back there. The saturated fats are the ones from animal and dairy products.
DR. WALTER WILLETT: That's right.
MARGARET WARNER: Meat, butter, and so on.
DR. WALTER WILLETT: Right. That's a main source of saturated fat.
MARGARET WARNER: The next category.
DR. WALTER WILLETT: The next category is mon unsaturated fat. Actually, a good amount of this also comes from animal fats, but it's most concentrated in the form of olive oil or canola oil. And that seems to be somewhat beneficial compared to carbohydrate. The best type of fat seems to be polyunsaturated fat from many liquid vegetable oils.
MARGARET WARNER: All right Now, Ms. Howard, what is your take on this basic finding, that it really isn't how much fat you eat but the type of fat?
BARBARA HOWARD, American Heart Association: Well, I really think that this study confirms what we've been telling people all along. And contrary to your initial introduction, the message from the American Heart Association has been to not smoke, to exercise, to control your blood pressure, and to eat less saturated fat and cholesterol. That's the message that we've been sending. And we've been telling people to eat moderate amounts, keep the fat intake below 30 percent fat. And I really think, by and large, this study has substantiated that in a very exciting way because before that we were basing our recommendations mainly on short-term feeding studies when I and many other people would bring people in, feed them a diet for six months, measure their cholesterol and other intermediate end points, and draw assumptions from that that we were really preventing heart disease. This actually looks at the end point of heart disease and tries to relate it back to what people are eating. So it's very exciting from that point of view.
MARGARET WARNER: But, Dr. Willett, are you--does your study say that it no longer matters if you keep your 30 percent--if you keep your fats below 30 percent of your diet, as long as it's all in olive oil and sunflower oil, I mean, would you go that far?
DR. WALTER WILLETT: Yes. I think that's what the data shows. And actually I think that's what the kinds of feeding studies that Dr. Howard has conducted and many other people have conducted actually show that it's really not the total percentage of calories from total fat in a diet, but it's really the type of fat, and that in most of the studies actually people with a higher fat intake did better than people with a lower fat intake as long as it was the right type of fat.
MARGARET WARNER: And so would you agree that the 30 percent doesn't really apply anymore?
BARBARA HOWARD: No, not totally because I think the end point that he was looking at was only heart disease. And you really need to look at the overall health of people. There's been a lot of work in the cancer field suggesting that high fat diets may, in fact, increase the risk for cancer, and then we have to worry about the terrible obesity problem we have in this country. People are eating too much, and it's easier to eat too much on a high fat diet.
MARGARET WARNER: What about that point, Dr. Willett?
DR. WALTER WILLETT: Well, I did part, I guess, company a little bit there because there was a hypothesis that higher fat diets were a major cause of cancer, but as the data have come in over the last decade, that just has not been supported. It's possible with prostate cancer there might be some excess risk with animal fat but there's really not been any evidence that the vegetable fats, the good types of fat for heart disease had an adverse effect for cancer. For obesity there has been a widespread myth that the percentage of calories from fat in the diet is a major cause or major determinant of how fat we are, but there have been many studies, randomized trials, that have looked at the percentage of calories from fat in relation to weight or weight change over a year or two period, and there's been little, if any, in effect. What is important is calories, and, unfortunately, people have been given the impression that calories from carbohydrate don't count. You can eat as much as you want to and you won't get fat. Indeed, we've been going on a national low fat diet. At the same time, obesity has almost exploded.
MARGARET WARNER: Well, that's true. Isn't it, I mean, as the setup showed, Americans' consumption of fat has actually come down quite a bit, and yet, Americans are heavier than ever, aren't they?
BARBARA HOWARD: Americans' consumption as a percentage of total calories has come down, but the absolute amount of fat people are eating is as much because they're eating more calories. And so I think that is the issue that we really have to think about is what does the average person do, and they're trying to cut their calories, and it is generally easier--the studies that Dr. Willett alluded to were controlled studies comparing high fat and high carbohydrate diets where calories were kept constant. But in the real world, when a person goes out and tries to eat something in front of them, generally it will be more satisfying if it has more bulk, and fat calories tend to be very concentrated and very tasty and, therefore, you tend to overeat them. However, I want to say one more thing, and that is I totally agree that this push toward an ultra low fat diet has led people into the fat substitutes. They go to the bakery counter, and they instead of buying a cupcake, they buy a no-fat cupcake, which has just as many calories because it's full of calorie-dense, sweet substitutes. So there--it's a complicated issue for the consumer.
MARGARET WARNER: Dr. Willett, what about the consumer here? Now, many people watching this show had switched to margarine years and years ago because other studies show that it was much better for them than butter. How definitive is your study? Why should they believe your study now versus these others?
DR. WALTER WILLETT: Well, the reality is that there were not other studies that showed that margarine was a lot better than butter. There was this sort of implication because saturated fat was bad that anything else was good for us. In fact, there were not such studies that really showed that margarine either created a better blood cholesterol picture, or that it reduced heart disease. In fact, a recent study has been conducted that compiled all the different studies comparing margarine versus butter, and it's clear that the older stick type of margarine was at least as bad as butter, but newer margarines that are lower in trans fat actually are better. In fact, just during the last few weeks there have been several margarines introduced to our market, which are free of trans fatty acids. And these are probably almost as good as liquid vegetable oils.
MARGARET WARNER: All right. So, just on this narrow question of whether people--as they get ready to make their Thanksgiving dinner they should throw out the margarine and use butter, I mean, what should they do?
DR. WALTER WILLETT: I don't think any of us would think that that would be a good recommendation to do, although, in fact, if it's the one time of the year you enjoy a little butter and you like that, that really doesn't make much difference. It's what we do on a day to day basis that counts. But if you really want to do the best thing, try a little bit of olive oil on your bread.
MARGARET WARNER: And what do you say to Americans who are confused by these studies that just keep coming out, and sometimes seem to certainly conflict with at least advise they've been given from their doctors?
BARBARA HOWARD: Well, I think they need to stick to the basic advice that has been given by the Heart Association by the Diabetes Association, by the National Heart, Lung, & Blood Institute; and that is to control their intake of saturated fat and cholesterol and total calories, and to eat a balanced diet with a variety of foods, with lots of fruits and vegetables and fiber. Now, the margarine issue, I'd like to comment on that because what has happened if some of it because of Dr. Willett's studies in the past is the food industry has very quickly responded, and really are producing now margarines and claim that by the end of next year none of the margarines will have trans fatty acids in them. So I think when people go to the dairy counter, I still think they're wise choosing a soft margarine as opposed to butter, especially if they're going to eat a lot of it, because there's a lot of saturated fat and cholesterol in butter.
MARGARET WARNER: All right. Well, thank you both very much for being with us.