The World Health Organization came out with a recommendation to keep intake of added sugars at less than 10 percent of total calories. The U.S. Department of Agriculture advises a limit of 10 teaspoons of added sugar a day (based on a 2,000-calorie diet). The Institute of Medicine recommends that sugar comprise not more than 25 percent of daily calories.

Yet Americans are still consuming approximately 20 percent of their diets as "added" or "free" sugar — about 20 to 30 teaspoons each day.

So, is sugar bad for you or not?

For starters, we are biologically programmed to like sweet things. This preference actually protected our ancestors from eating poisonous foods, which tend to be sour.

Sugars, starches and fiber are all members of the nutrient category carbohydrates, the body's main source of fuel. (The WHO recommends that carbohydrates make up 55 to 75 percent of daily intake.) All carbohydrates — fruit, vegetables, starches, milk products — contain some natural sugar. For example, milk contains lactose, fruits and vegetables contain fructose and glucose, and grains contain chains of glucose linked together.

The body converts carbohydrates to simple sugars, an energy source. "Sugars can be part of a healthful diet, in moderation," said Barbara Rolls, professor of nutrition at Penn State University and author of "The Volumetrics Weight-control Plan" (Harper Mass Market Paperbacks, 2002). "In fact, naturally occurring or added sugars can make nutritious foods more appealing by adding taste, aroma, texture and color."

So why reduce sugar in your diet? Do we become fat from eating it? Does it cause diabetes? Cavities? Does eating a lot of sugar make you look older (the "Perricone Prescription")? Can you become addicted to sugar?

Some would argue that an unequivocal yes to these questions would be perpetuating a myth, but that's not what experts find most disconcerting. The type of sugar that experts take issue with is not what is naturally found in food, but the added or free sugar, which is added to improve taste.

Researchers say this sugar is no worse than natural sugars, in itself. "The body can't tell if you have eaten table sugar or sugar from a fruit — it all gets converted to glucose," said Christopher Gardner, director of nutrition studies at Stanford Center for Research in Disease Prevention. Some research does suggest that high fructose corn syrup (often used by manufacturers as a sweetener) is stored more easily as fat than sucrose, and may be less filling.

But the type of sugar is not the point, said Gardner. "It's what they're NOT consuming that's important. If they're eating foods with added sugar, the healthier foods are being knocked out." When a diet is high in added sugar, the intake of critical nutrients is reduced, putting the individual at higher risk for cancer, osteoporosis, heart disease and other conditions.

You can't just take a vitamin to make up for what you're missing, say the experts. "Foods such as fruits and vegetables have benefits that we are just beginning to learn about that can't be replaced by a pill," Gardner said.

It's surprising to see all the foods that have added sugar. Look at the label on ketchup, applesauce, soups, cereals, baby food, salad dressing or whole-wheat bread. Even the Slim-Fast shake that's supposed to help you lose weight has almost 9 teaspoons of sugar.

Unfortunately, the label lists only the total sugar content in a product, so there's no way to know how much of that sugar has been added during manufacturing.

To minimize your sugar intake, you have to be a bit of a detective.

• Learn about added sugar: First, you need to be able to determine what the recommended limit of 10 teaspoons of sugar or 10 percent added sugar means. A teaspoon of sugar contains about 4 grams, so 10 teaspoons would put your upper limit at about 40 grams per day. Since a gram of sugar has about 4 calories, that means you are aiming to keep your total calories from added sugar at no more than 160 calories. Using the WHO's recommendation, that would be 50 grams for a 2000-calorie diet, or about 12 teaspoons.

• Check the ingredient list: Food labels list ingredients by weight, in descending order. If sugar is one of the first few ingredients listed, this may be a product you want to avoid. Be on the lookout for sugar's many aliases: sucrose, high-fructose corn syrup, corn syrup, confectioner's sugar, corn sweeteners, dextrose, glucose, fructose, maltose, molasses, honey, brown sugar, fruit and juice concentrate, invert sugar, cane sugar, raw sugar, galactose, lactose, levulose and maple sugar.

• Stay away from that liquid candy: Cut back on sugary soda intake. It provides no nutritional value, and just two sodas per day could add 30 pounds to your weight in a year. Juice is another high-calorie beverage to limit. One cup contains the natural sugar of several pieces of fruit, without the fiber or fullness factor of real fruit.

• Carefully check sweets and foods that claim to be free of fat: Carefully read labels of low-fat and fat-free foods. Many use sugar to enhance taste and texture once the fat has been removed. Even seemingly healthful foods such as yogurt can be high in sugar. For example, Stonyfield Farm Nonfat Strawberry Yogurt may be fat-free, but it has 31 grams of sugar for a 6-ounce serving.

• Be dense: Choose dense foods that provide nutrients besides sugar or fat and have been minimally processed, such as whole grains, fruits, vegetables, lean meats, low-fat dairy and heart-healthy fats. Make sure sugar is not high on the ingredients list for packaged foods.

• Carefully check foods that say "sugar-free" or have no added sugar: Try foods that are sugar-free — as long as you monitor the fat content. Look for "No Added Sugar" and "Without Added Sugar" claims. A food is allowed to boast this on the label if no sugar or sugar-containing ingredient (such as fruit juices, applesauce or dried fruit) is added during processing or packing. But remember, the package can be labeled this way even if the food is not low in calories.