Artificial sweeteners, or sugar substitutes, are chemicals added to some foods and beverages to make them taste sweet. People often refer to them as “intense sweeteners” because they provide a taste similar to that of table sugar but up to several thousand times sweeter. 

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Critics of artificial sweeteners say that they cause a variety of health problems, including cancer. That's largely because of studies dating to the 1970s that linked the artificial sweetener saccharin to bladder cancer in laboratory rats. Because of those studies, saccharin once carried a label warning that it may be hazardous to your health.

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But there are some data that suggest artificial sweetener users don’t always lose weight, and that they may not be armed against diabetes. The body reacts to artificial sweeteners differently than it does to sugar — the healthy bacteria that live in the gut, for example, change when these compounds are around — and the consequences might be both surprising and unwelcoming, especially for children.

When choosing sugar substitutes, it pays to be a savvy consumer. Artificial sweeteners are not magic bullets. Food marketed as sugar-free isn't calorie-free, so it can still cause weight gain. Keep in mind that processed foods, which often contain sugar substitutes, generally don't offer the same health benefits as whole foods, such as fruits and vegetables.