And that really is just about all you have to know. Sure, books can be useful. They go into great detail, if you're curious, and they reinforce one's beliefs. One can feel more assured, knowing that the experts agree.

There are many interesting areas of controversy, but the real benefits are going to come from looking at the things the experts agree on. There's a general agreement that a diet high in fats and cholesterol promotes heart disease. There's general agreement that a high salt diet makes hypertension worse. There's growing evidence that a diet high in any kind of fat promotes colon and breast cancer. There's a growing feeling that a low-fiber diet may be related to increased incidence of colon cancer and diverticulosis, and that a high-fiber diet can help prevent obesity. Low-sugar, low-fat, high-fiber foods are generally higher in nutrients and a good deal less expensive than sugary, fatty processed foods, so there's certainly no way they're going to hurt anybody.

Three health problems—heart disease, hypertension, and colon and breast cancer—account for about 50 percent of all deaths. Tooth decay costs society about three billion dollars a year. So in sticking to the areas in which there's general scientific agreement, we've also focused in on the areas where some basic dietary changes will result in a longer, healthier life.

What proportion of the general public could improve their health by following these guidelines?

I'd say at least two-thirds. And that may be a conservative estimate

What's the one most important thing people can do to improve their diet?

For most people, it's probably to reduce the total intake of fat. I'd guess that if you went out on the street right now and asked a hundred people what was the single worst thing in their diet, most of them would say sugar. But fat is much more of a hazard than sugar, because of the strong links between fats and our number-one killer, heart disease. I think fat has to be the number-one focus for just about anyone who's starting to look at his or her diet—how much fat do I consume and how can I reduce my daily fat intake? Most people realize that red meats and fried foods contain a lot of fat. Not so many realize that eggs, butter, whole milk, Swiss cheese, coconut, avocados, peanut butter, nuts, soybeans, tofu, and many baked products are also high-fat foods.

What's the best way to go about making changes in one's eating patterns?

I think the easiest thing is to go at it gradually—to change your diet just a little bit at a time. There's no one way to do it. People need to experiment to find what works best for them. One place to start, if you're a milk drinker, is to switch from regular milk to low-fat, and maybe eventually to skim milk.

Another good approach is to begin to think about nutrition when you're buying your food. When I go shopping now, I limit myself to nutritious foods—and I make sure to buy a wide variety of nutritious foods, so that if I'm in the mood for something crispy, I'll have something crispy in my kitchen. If I'm in the mood for a cold liquid, I'll have that. I'll have something cold and something hot. And I'll have the raw ingredients to make a wide variety of nutritious meals.

You know that if candy bars and potato chips and soda pop go into your shopping cart, they're going to be eaten. On the other hand, if you have a wide variety of nutritious foods around, you can find something to satisfy every kind of eating mood, so you won't end up feeling deprived. Change your diet slowly, and keep a lot of different good foods around.