New study explores sweet perception, preferences

THE LEVEL of sweetness most preferred in foods and beverage does not change even though foods such as vanilla pudding taste sweeter after a low-sugar diet for a period of three months. This finding of a new study conducted by scientists at the Monell Center and collaborators can be used by public health initiatives to cut the amount of added sugars people consume in their diets.

Humans generally like sweet taste. Scientists, however, have yet to obtain a clear understanding of how sugar consumption influences perception of and liking for sweet foods and beverages.

The current study, published online ahead of print in the American Journal of Clinical Nutrition, addressed the role of dietary experience by looking into whether a person’s sweet taste perception and preference can be shifted by reducing the amount of sugar consumed in their diet. Meanwhile, a genetic component to sweet taste perception demonstrated in a recent paper co-authored by Monell scientists accounted for only about 30% of person-to-person variance.

According to study lead author Paul Wise, a sensory psychologist at Monell, “Overconsumption of sugar is widely believed to contribute to obesity and related health problems such as heart disease. If people could adjust to a lower-sugar diet over time without affecting food acceptance, it might be possible to gradually reduce added sugars in food and beverages without causing rejection.”

(Photo: Colin Stitt I Dreamstime Stock Photos)

The research, funded by PepsiCo and Monell Center institutional funds, involved healthy adults typically consuming two or more sugar or high fructose corn syrup-sweetened soft drinks daily but not using non-nutritive sweeteners on a regular basis. After a one-month baseline period, 16 subjects from the ‘control’ group maintained their normal diet and sugar intake over the next three months. Meanwhile, 13 subjects forming the ‘reduced-sugar’ group maintained their baseline caloric intake while replacing 40% of calories from sugars with fats, proteins, and complex carbohydrates over the same time period. Both groups were guided by a dietician.

Tests were conducted at the end of each month to rate sweet taste intensity and pleasantness of sweetened vanilla puddings and raspberry beverages, both of which were prepared using a wide range of added sucrose (table sugar). The subjects rated most puddings as sweeter than did individuals not sugar-restricted after three months on the reduced sugar diet. A similar effect was seen for low concentrations of the beverages.

The findings indicated three months of sugar restriction did not influence the amount of sucrose most preferred in the pudding, which averaged 32.4% for the reduced-sugar group and 31.2% for individuals who maintained their normal diet, despite the difference in sweetness ratings. The preferred level of added sucrose in raspberry beverage did not differ between the two groups, averaging 13.5% for the reduced-sugar group and 13.9% for the control group.

The participants were allowed to choose their own diet on the fifth month of the study. Those from the reduced-sugar group quickly increased their sugar intake to baseline levels. Their ratings of sweet taste intensity reverted to pre-diet levels.

Wise said, “People who had been on a low-sugar diet for three months quickly went back to their previous sugar levels when given a choice. This rapid rebound suggests that people may resist changes in the sugar level of their diets.”

Previous Monell studies examining the effect of dietary salt intake on salty taste perception and preference yielded different results, with both perception and pleasantness changing with reduced amount of salt consumed over several months. Subjects on a low-salt diet came to prefer lower levels of salt in their food.

Study co-author Gary Beauchamp, PhD, a behavioral biologist at Monell, noted the factors that underlie liking for sugar and salt may differ.

“The salt findings formed part of the rationale for the National Academy of Sciences’ recommendation to decrease salt consumption by gradually lowering the amount of salt in prepared and restaurant foods. Modern diets contain a large proportion of calories as sugar, but this same tactic may not work as well to help reduce the amount of sugar that people consume,” said Dr. Beauchamp.

The researchers are hoping to use a larger group of participants to find out whether a longer period on a low sweetener diet may eventually change preferences for sweet foods.

“It also will be interesting to know whether the critical factor is the overall level of sweetness in the diet or the amount of sugar consumed,” said Wise.

The research included contributions from Laura Nattress and Linda J. Flammer of Pepsi Global R&D also contributed to the study. PepsiCo played no role in design, data collection, data analysis, or interpretation.

Philadelphia, Pennsylvania-based Monell Chemical Senses Center is an independent nonprofit basic research institute that has for more than 47 years advanced scientific understanding of the mechanisms and functions of taste and smell to benefit human health and well-being. Scientists here use an interdisciplinary approach to collaborate in the programmatic areas of sensation and perception, neuroscience and molecular biology, environmental and occupational health, nutrition and appetite, health and well-being, development, aging and regeneration, and chemical ecology and communication.