It's not good for us, providing only empty calories, causing tooth decay and obesity.

Sugar sweetens our day. Coffee, tea and cake often do not appear on the table without it. But refined white crystals are not the only form of sugar - it is also hidden in many foods. To avoid succumbing unwittingly to this energy-rich seductress, experts advise caution when sweetening.

In addition to white table sugar, or sucrose, which is industrially manufactured from refined sugar cane or sugar beets, there are sugar substitutes such as fruit sugar, or fructose, and grape sugar, or glucose.

"Honey, syrup and juice concentrate are also 60 to 70 percent sugar," says Gisela Olias of the German Institute of Human Nutrition (DIfE).

But if you think you are doing yourself a favor by putting honey in your tea instead of the same amount of sugar or rock candy, you are mistaken, warns Achim Bub of the Federal Research Institute of Nutrition and Food.

"Whether you use table sugar, honey, syrup or fruit juice concentrate is mainly a personal or philosophical matter. All of them cause tooth decay," Bub remarks. Sugar, he says, cannot be divided into "healthy" or "unhealthy" varieties. Diets can, though.

Antje Gahl, a home economist at the German Nutrition Society (DGE), says that sugar, sugar substitutes and artificial sweeteners should be used in moderation. She also contradicts what she says is the still widespread fallacy that fructose is better for you than common table sugar. Fructose is neither more healthy nor less energy-rich, she says, and contains, like table sugar, no vitamins or minerals.

"That's why sugar is commonly said to provide empty calories," she says. Fructose is often used in special products for diabetics. "Professional associations now classify these diet products as nutritionally and diabetologically unnecessary," Gahl says. In other words, diabetics, like other people, should have a balanced diet and do without special products for diabetics.

Studies by Germany's Federal Institute for Risk Assessment have shown that fructose has no appreciable advantages over other sugars. Hence it is not recommended, Gahl says. Other studies have also shown that diet products are often more expensive than normal ones and contain a higher proportion of fat. Regularly consuming diet products is risky, Olias warns.

"People think they're cutting down on energy because they see the word 'diet'," she says. If you have been lulled into a false sense of security, it is easy to eat large amounts - and more calories and fat - without realizing it. "You quickly end up being overweight," Olias says.

To sweeten food and drinks without adding calories, you have to use artificial sweeteners. In contrast to sugar, honey, syrup and other sugar substitutes, artificial sweeteners are manufactured chemically and have significantly greater sweetening power.

Concerns that artificial sweeteners are harmful to health are unfounded, experts say. Their safeness, the DGE points out, is thoroughly tested before they are approved for marketing.