Mary Poppins knew this secret: We are born with an innate preference for sweetness. As she often sang, "A spoonful of sugar makes the medicine go down."

Trouble is that few people stop with a spoonful. A new report in the Journal of the American Dietetic Association notes that despite an obesity epidemic, Americans still eat more foods with added sugar and fat than they should and often fall short on healthy fare. No surprise there.

Sugar substitutes and other sweeteners have been around for decades. But thanks to a growing number of enhanced products, it's possible for everyone -- even the estimated 71 million Americans dieting -- to soothe a sweet tooth without exceeding their daily calorie goals. That's good because the average adult has only about 200 so-called "discretionary calories" per day for food and beverages with added sugar, added fat and alcohol.

In 2007, an estimated 194 million Americans consumed products sweetened with sugar substitutes, according to the Calorie Control Council, an industry group. That's 14 million more than in 2004. The council reports that the most popular are sugar-free or reduced-sugar beverages, ice cream and desserts, chewing gum and sugar substitutes spooned into coffee or tea.

Sugar substitutes and alternative sweeteners promise flavor with few or no calories. Also on the market are "natural" sweeteners such as Whey Low. It's made from fructose, the sugar found in fruit; sucrose, ordinary table sugar; and lactose, the non-sweet-tasting sugar found in dairy products. At just 4 calories per teaspoon, Whey Low pours and bakes just like sugar, but with 75 percent fewer calories. (There is also a Whey Low without sucrose for people with diabetes.)

Blue agave nectar is another natural sweetener that is growing in popularity. It's extracted from a cactus-like plant. But at 15 calories per teaspoon, it has just one fewer calorie than table sugar; six fewer than honey. Agave nectar is touted for being sweeter tasting than either sugar or honey, so that smaller amounts can be used. It is also purported to have a lower glycemic index, which means it may raise blood sugar less than the others. (If you have diabetes, check with your doctor before using this product.)

Calories are one thing. Safety is another. In 1970, the Food and Drug Administration (FDA) banned cyclamates, a widely used sugar substitute, because of cancer concerns. In 1977, a Canadian study found that saccharin -- the sweetener still found in Sweet'N Low -- caused bladder cancer in rats. The FDA considered banning saccharin but Congress stepped in to give the sweetener a reprieve and has extended a moratorium on its ban several times since then.

In 2004, the American Dietetic Association reviewed the use of sweeteners and concluded that "consumers can safely enjoy a range of nutritive and non-nutritive sweeteners when consumed in a diet that is guided by current federal nutrition recommendations."

Concerns about two substitutes

Since then, some concerns have arisen about two sugar substitutes: acelsulfame K and aspartame.

Aspartame is marketed as NutraSweet and Equal, and found in a wide range of products from diet drinks to sugar-free ice cream. Aspartame contains amino acids -- the building blocks of protein -- and methanol, an alcohol. It isn't heat-stable so it doesn't do well in baking. An Italian research team found lymphoma and leukemia among female rats in a long-term study of aspartame.

Acesulfame K, also sold as Sunnett, is not metabolized by the body and so contains zero calories. It's found in baked goods, diet soft drinks, sugar-free gum and Sweet One, a sugar substitute for baking. In 1996, the Center for Science in the Public Interest urged the FDA to require better testing before permitting acesulfame K in soft drinks. Large doses of a breakdown product from acesulfame K have been shown to affect the thyroid of rats, rabbits and dogs, CSPI notes.

Manufacturers, the FDA and the Calorie Control Council say that these products are safe. But in the May issue of Nutrition Action, CSPI called these products and saccharin either unsafe or poorly tested. The only artificial sweetener to get a "safe" grade from the consumer advocacy group is sucralose, better known as Splenda.

Bottom line: If you're looking for sweetness with fewer calories, reach for a variety of products to hedge your nutritional bets.

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