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Aspartame, sucralose, acesulfame potassium, stevia: From yogurt to diet pop, artificial sweeteners and sugar substitutes are everywhere, appealing to the growing number of consumers who want to watch their weight. Despite the sweeteners' ubiquity in the grocery aisles, however, there's no end to the confusion about their safety.

Companies that sell artificial sweeteners, or foods made with them, assert they are harmless. Advocacy groups, such as the Washington, D.C.-based Center for Science in the Public Interest, cite studies that link some of them to cancer. The sugar lobby (yes, such a thing exists) argues artificial sweeteners are inferior to the real article. Then there's the conspiracy theorists who liken sugar substitutes to poison.

The issue

In the 1960s and 70s, research emerged suggesting artificial sweeteners such as cyclamate and saccharin might cause cancer in lab rats. Since then, other studies have raised similar concerns about aspartame and acesulfame potassium.

Many credible experts with no ties to the food industry dispute those findings, however, saying they were based on an unrealistically high consumption of artificial sweeteners.

For instance, Yoni Freedhoff, medical director of Ottawa's Bariatric Medical Institute and an expert on obesity issues, argues artificial sweeteners have been poked and prodded in countless studies, yet none have definitively concluded they pose any health risks to consumers. He also takes issue with studies that link consumption of artificial sweeteners to weight gain as those studies typically fail to take into account the overall quality of an individual's diet. In fact, Dr. Freedhoff believes artificial sweeteners are a good alternative for people who want or need to lose weight.

But there are emerging concerns that sugar substitutes may have a long-term impact on how the body registers sweet tastes, which could make weight management more challenging.

There is growing evidence that the intensity of artificial sweeteners (typically much sweeter than sugar) can rewire taste receptors. And this can cause distaste for less-sweet foods, such as fruits and vegetables, according to David Ludwig, director of the New Balance Foundation Obesity Prevention Center at the Children's Hospital Boston.

New research also suggests consuming diet drinks may disrupt the body's natural ability to associate sweetness with caloric intake and a feeling of fullness. And this could lead to changes in how the body regulates hunger, Dr. Ludwig wrote in the Journal of the American Medical Association. One study found that rodents fed saccharin consumed more calories and gained more weight than those fed glucose or sugar.

More research comparing the long-term effects of consuming sugar-sweetened, artificially-sweetened and unsweetened beverages is needed. Until then, there will be no clear-cut answers, Dr. Ludwig said.

On the horizon

Stevia, a plant that grows in Paraguay and Brazil, has been getting plenty of buzz as an alternative to chemically produced artificial sweeteners. A natural, no-calorie sweetener derived from stevia isn't allowed to be added to food sold in Canada but the plant's leaves can be sold directly to consumers.

Health Canada has approved stevia for use in some natural health products. Dr. Ludwig said there's a difference between the traditional stevia leaf and the extracts many companies are using as food additives. Just because it's natural doesn't mean it's safer, and rigorous studies may be needed to assess the long-term safety of stevia extracts as well.

The bottom line

In the meantime, Dr. Ludwig says artificial sweeteners should be considered "transitional" aids to help a person move from high-calorie, sugary drinks to minimally sweetened beverages, such as mineral water or tea.

The Canadian Cancer Society advises consumers to use artificial sweeteners in moderation because some evidence has linked them to cancer in lab animals. Although these studies haven't been replicated in humans, the society advises caution.

This is a new monthly column that investigates the claims behind health products and food.