Ask the doctor: Are artificial sweeteners a good alternative to sugar?

Q. More and more nutrition advice seems to be anti-sugar these days. So are artificial sweeteners a good alternative?

A. Sugar in all its forms may be the single most important dietary cause of obesity and heart disease in the American diet today. Stripped of fiber and antioxidants, table sugar (sucrose) and high fructose corn syrup cause big jumps in blood glucose and insulin that raise levels of triglycerides, various inflammatory markers, and free oxygen radicals. In addition, the fructose found in most types of sugar may damage the liver and cause insulin resistance.

The FDA has approved five artificial sweeteners: acesulfame, aspartame, neotame, saccharin, and sucralose. Stevia is a plant-derived noncaloric sweetener that also has FDA approval. Though concerns about cancer have been largely dismissed, these chemicals may cause headaches and other reactions in sensitive individuals.

Most people consume artificial sweeteners because they want to lose weight. Replacing concentrated sugar with products that have very few, if any, calories should tilt energy balance in favor of weight loss. And some short-term studies suggest that artificial sweeteners may have that effect.

But other research raises concern that they may do just the opposite and actually promote weight gain. How so? Artificial sweeteners are extremely sweet — hundreds to thousands of times sweeter than table sugar. So people who habitually consume them may wind up desensitized to sweetness. Healthful, satiating foods that are less sweet — such as fruits and vegetables — may become unappetizing by comparison. As a result, the overall quality of the diet may decline. The calories removed from the diet by the sugar-for-sweetener swap may sneak back in, in the form of refined carbohydrates and low-quality fats. In addition, some research has identified sweetness receptors in fat tissue. We don't know for sure, but that raises the possibility that artificial sweeteners could cause weight gain by directly stimulating the development of new fat cells. There's also some epidemiologic evidence of a correlation between artificial sweetener consumption and obesity, but it should be interpreted cautiously. People might consume artificial sweeteners because they've gained weight, not the other way around.

Our research group at Children's Hospital Boston is conducting a clinical trial sponsored by the National Institutes of Health that should help resolve questions about the relationship of artificial sweeteners to weight gain (or loss) and other health outcomes. We're recruiting 270 young adults, ages 18 to 35, who currently drink sugar-sweetened beverages and randomizing them to drink sugar-sweetened, artificially sweetened, or unsweetened beverages (the drinks are delivered free to their homes). We'll examine changes in body weight and heart disease risk factors at the end of the one-year intervention. Please call 617-355-2500 if you wish to participate.

At the Optimal Weight for Life (OWL) clinic here at Children's, we recommend artificial sweeteners only as a transitional aid to wean people off sugary beverages. And personally, I avoid artificial sweeteners. For me, fresh fruit in season and other natural sources of sweetness can't be matched by anything that comes from a factory.

— David S. Ludwig, M.D., Ph.D.
Children's Hospital Boston