Detecting, Liking and Wanting Sweetness

Those who read food labels realize that high fructose corn syrup is added to all sorts of products, from pickles to yogurt to spaghetti sauce. The Corn Refiners Association says this is because high fructose corn syrup enhances flavor and increases shelf life. A recent article in the journal Physiology and Behavior suggests that there may be another reason.

The article, called Modified sham feeding of sweet solutions in women with and without bulimia nervosa, was designed to show whether people who experience binge-eating episodes might overrespond to the stimulations of taste and smell. As it turns out, they do not, or at least they did not in this study. However, the study did produce an interesting outcome in terms of the way people respond to sweet tastes.

The study compared two groups of women--ten healthy women (termed NC, or Normal Control) and eleven women with Bulimia Nervosa (termed BN). The women were given solutions of cherry-flavored Kool-Aid sweetened with aspartame in concentrations of 0, 0.01, 0.03, 0.08 and 0.28%. (The 0.08% solution approximates the sweetness of commercial soda.) There were three trials in which the five solutions were prepared in five opaque containers, each fitted with a straw. The solutions were presented in a random order, using a one-minute access period during which the women could sip as much as they wanted of that particular solution, but they could not swallow it. They were instructed to spit out the solution into another opaque container. (The amount sipped and the amount spit out was later measured by the investigators.) The women were then asked to

1. Rate the sweetness of the solution

2. Rate how well they liked the solution

3. Rate how much they wanted more of the solution

Even though the solutions were presented in random order, both the Normal Control group and the Bulimia Nervosa group were able to accurately distinguish among the five levels of sweetness provided in the solutions. Again, although the solutions were presented randomly, both the Normal Control group and the Bulimia Nervosa group reported liking the solutions in direct proportion to how sweet the solutions were. Consistent with the self-reported preference rating, both groups sipped an increasing amount of the solution as the sweetness of the solution increased. (Remember, they were not allowed to swallow the solution, but they could sip as much of it as they wanted.) Finally, as shown in the graph below, both groups reported that they wanted more of the solution as the sweetness of the solution increased.
For both groups of women, more sweetness led to more liking, more sipping and more wanting. This was not a function of actually consuming the sweetened solutions, but simply of having the solutions in their mouths for a few seconds. Using this information, it not unreasonable to suggest that the increased use of another sweet substance, high fructose corn syrup, in all sorts of foods, may have the unintended result of producing more liking, more eating and more wanting of the products that contain it.