Sunday, January 11, 2009

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.


Cynthia1770 said...

My google alert for HFCS picked up your post. That's an interesting study. I only wish that the experimenters had used caloric sweeteners instead of aspartame.
Nevertheless, it's food for thought. I've always wondered why the CRA didn't choose to use HFCS-50 to sweeten major brands of soda.
That at least would have mimicked the fructose:glucose ratio in sucrose. Instead they chose HFCS-55
(55%fructose:45%sucrose), which has lead to long term health hazard. Maybe the CRA settled on HFCS-55 because it was sweeter, possibly a little more addictive?
Woops, that sounds like a conspiracy.
Take care

Stargazey said...

Hi, Cynthia! That's a good point about the caloric sweeteners. In the Materials section, the authors state, "pilot testing using sucrose solutions with women with eating disorders suggested that their concerns about the caloric content of sucrose solutions limited their intake, despite instructions to not swallow the solutions." Possible caloric intake might also limit the sipping behavior of normal women, who are often socialized to be weight-conscious.

Another factor is that the women probably did swallow minute amounts of the solutions, so a nutritive sweetener would have provoked various digestive responses. Because the investigators were only interested in the psychological effects of stimulation of taste receptors, the zero calorie aspartame was probably a better choice from that standpoint as well.

Anonymous said...

Sugar addiction! Its real Im sure.