You may find this surprising — I certainly did — but only about 15 percent of Americans regularly consume beverages and foods that contain artificial sweeteners.
Given the perpetual struggles in this nation with expanding waistlines, and the apparent popularity of diet sodas, I would have expected that at least half the population would routinely try to cut calories by choosing what scientists call non-nutritive sweeteners in place of caloric sweeteners like sugar (sucrose) and high-fructose corn syrup.
Experts offer several reasons people may be reluctant to make the switch. One, of course, is taste. People become used to foods and drinks tasting a certain way, and they won't or can't adapt to a new flavor. Try convincing a lover of regular Coke that Diet Coke tastes as good.
Another obstacle is the safety concerns about the federally approved non-nutritive sweeteners: aspartame (NutraSweet and Equal), saccharin (Necta Sweet), sucralose (Splenda), stevia (Truvia and PureVia), acesulfame potassium (Ace-K) and neotame (a relative of aspartame).
Forty years ago, saccharin and cyclamates came under scrutiny after a study found that the combined artificial sweeteners caused cancer in laboratory rats. That led to a federal ban in 1969 on cyclamates, a sweetener that is still marketed in more than 100 countries. Saccharin, rarely used in soft drinks, remains a popular tabletop sweetener despite a suspected link to bladder cancer.
Early on, aspartame was charged with causing headaches and other neurological problems, including seizures and brain tumors. Although some consumers may be sensitive to this sweetener, in 25 years of widespread use no human evidence of a link to cancer has emerged from prospective studies of diet and health.
A final issue is the role of non-nutritive sweeteners in appetite and weight control. I am not alone in having noticed that many overweight people drink diet sodas as if they were water. The question is: Does a weight problem prompt people to try to cut calories, or does the consumption of artificial sweeteners lead to their weight problem?
Behavior, not biology
In the current issue of The American Journal of Clinical Nutrition, Richard D. Mattes of Purdue University and Barry M. Popkin of the University of North Carolina reviewed 224 professional studies of the effects of non-nutritive sweeteners on appetite, food intake and weight. They acknowledge that the literature is rife with contradictory reports.
Nonetheless, they concluded that "taken together, the evidence summarized by us and others suggests that if non-nutritive sweeteners are used as substitutes for higher-energy-yielding sweeteners, they have the potential to aid in weight management."
But there's a rub. In the published report and in interviews, Popkin and other experts emphasized that these no-calorie and very-low-calorie sweeteners can aid in weight control only if people do not overcompensate by eating lots of high-calorie foods.
I've long been amused by diners who choose a dessert like apple pie a la mode, at about 600 calories a serving, and sprinkle artificial sweetener in their coffee or tea to replace the 16 calories in a teaspoon of sugar. If taste is the only reason, then go for it. Otherwise, this trade-off makes no sense.
"Used prudently, non-nutritive sweeteners can work," Popkin said. "We feel that after water and noncaloric teas and coffees, diet beverages are completely safe and should be consumed by people trying to lose weight or keep from gaining. In the real world, however, a lot of people don't do it properly, and they gain weight drinking diet sodas because they use them as an excuse to eat more high-calorie foods.
"It's more a behavioral issue than a biological one," Popkin said. "Some people use non-nutritive sweeteners as a crutch; other use them to help create a healthy diet."
Still, some researchers believe that non-nutritive sweeteners can be responsible for that crutch because sweetness, regardless of its source, begets an increased desire for sweet-tasting foods. Some scientists maintain that an attempt to fool the body by divorcing the sweet taste from the calories that would normally be in a sweet food creates a craving for real calories.
For example, in recent widely publicized studies in rats, Susan E. Swithers, a psychologist at Purdue University, compared the results when animals were given either caloric sweeteners or saccharin with a regular, unrestricted diet. Those given saccharin gained more weight and more body fat because they overcompensated for the noncaloric sweetener, Swithers said in an interview. A possible reason, she suggested, is the failure of saccharin to raise the animals' core temperature as much as a caloric sweetener does.
"The experience of the sweet taste no longer has the expected consequences," Swithers said. "We don't know if humans react in the same way because no one has tested this idea in humans."
Why waste calories?
But as Dr. George Blackburn put it, "Man is not a rat." Blackburn, director of the Center for the Study of Nutrition Medicine at Beth Israel Deaconess Medical Center in Boston, said that when people were motivated to lose weight, non-nutritive sweeteners could help.
In one of the largest and longest studies, Blackburn and his colleagues at Beth Israel found that among dieters who were randomly assigned to consume liquid calories or artificially sweetened drinks for 175 weeks, those who drank the diet drinks took in 100 fewer calories a day and lost significantly more weight and kept more of it off.
"Those 100 calories add up to 10 pounds a year," Blackburn said. "Small changes in caloric intake can result in small but meaningful healthier weights. Most people would be happy with that."
Dr. Barbara Rolls and her colleagues at Pennsylvania State University have done short-term studies using non-nutritive sweeteners as sugar substitutes to reduce energy intake. They found them effective "when used as a real substitute and not an excuse to eat a lot of other things," Rolls said. "Why waste the calories?"
In a 19-month observational study among 548 middle-school children by Dr. David Ludwig and colleagues at Harvard, each added serving of sugary soft drink daily increased the obesity risk 60 percent. The children who drank diet drinks did not gain weight. A six-month follow-up study found that overweight children given noncaloric drinks lost significant weight compared with those who consumed their usual soft drinks.
Adam Drewnowski, director of the Center for Public Health Nutrition at the University of Washington in Seattle, said the diet soda and weight issue must consider economics.
"Regular soft drinks are largely consumed by lower income groups, who are more likely to be obese, whereas diet soft drinks tend to be consumed by more upscale people, who tend not to be obese," he said in an interview. "What contributes to the obesity — is it the drink or socioeconomic status?"