Which foods don't belong in a healthy diet?

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What exactly is a healthy diet? The basics are pretty simple. Everyone needs a mix of proteins, carbohydrates, and fats, plus enough vitamins and minerals for optimal health. But science is revealing that some of the food choices within these categories are better than others.

Are there foods you never should eat? Not really. If you crave an ice cream sundae occasionally, have a small one. But don't make it a daily event. Offset the chips you ate at your neighbor's barbeque with healthier snacks at home. Healthy eating doesn't mean eliminating certain foods altogether. However, there are some things that are best eaten only rarely.

Get your copy of Healthy Eating Eat real food. That’s the essence of today’s nutrition message. Our knowledge of nutrition has come full circle, back to eating food that is as close as possible to the way nature made it. Based on a solid foundation of current nutrition science, Harvard’s Special Health Report Healthy Eating: A guide to the new nutrition describes how to eat for optimum health.

Harvard nutrition scientists have compiled the following list of foods you should keep to a minimum. Research suggests that eating these foods regularly (and to the exclusion of healthier choices) can set the stage for life-threatening illnesses such as heart disease, high blood pressure, diabetes, and even some cancers.

Added sugar. Whether it's white granulated sugar, brown sugar, high- fructose corn syrup, corn sugar, or honey, sugar contains almost no nutrients and is pure carbohydrate. When you eat a lot of sugar you are filling up on empty calories, causing your blood sugar to rise and fall like a roller coaster, and can keep you from eating foods that with important nutrients and fiber.

Research cites soft drinks and other sugar-sweetened beverages as the primary source of added sugar in the American diet and a major contributor to weight gain. In fact, just one extra 12-ounce can of a typical sweetened beverage a day can add on 15 pounds in a year. That's not only because the drinks themselves add calories, but also because those liquid calories aren't as satisfying as solid food.

Dairy fat. Ice cream, whole milk, and cheese are full of saturated fat and some naturally occurring trans fat and therefore can increase the risk of the health problems, notably heart disease. The healthiest milk and milk products are low-fat versions, such as skim milk, milk with 1% fat, and reduced-fat cheeses.

Baked sweets. Cookies, snack cakes, doughnuts, pastries, and many other treats are hard to pass up, but these commercially prepared versions are packed with processed carbohydrates, added sugar, unhealthy fats, and often salt.

White carbohydrates. Bread, pasta, potatoes, rice, cookies, cake, or pancakes — if you enjoy these foods, opt for whole-grain versions. Yes, you can find or make whole-grain pancake mix. Whole-wheat pastas and breads are luckily easy to find. And you can always make your own homemade cookies or bars using grains such as oatmeal, and less sugar and unhealthy fats.

Processed and high-fat meats. Shun the cold cuts and "pigs in a blanket." Despite some conflicting reports, the balance of the evidence confirms that processed meats like bacon, ham, pepperoni, hot dogs, and many lunch meats are less healthy than protein from fish, skinless chicken, nuts, beans, soy, and whole grains. Fresh red meat should be eaten sparingly and the leanest cuts selected.

Salt. Current dietary guidelines and the American Heart Association recommend reducing sodium to 1,500 mg per day and not exceeding 2,300 mg per day. But most of us get 1½ teaspoons (or 8,500 mg) of salt daily. That translates to about 3,400 mg of daily sodium. Your body needs a certain amount of sodium, but too much can increase blood pressure and the risk of heart disease and stroke.

If you want to learn more about the health benefits of a good diet and how to eat more nutritiously buy Healthy Eating, a Special Health Report from Harvard Medical School.