If you are someone who has adopted a low-carbohydrate diet or reduced intake of sugar in its various forms, was there a point where you realized that you no longer care for sweet foods and beverages? It was as if your body became accustomed to eating less sweet foods and over time this led to a change in sweet preference.

Thanks to funding by PepsiCo, whether lowering dietary sugar intake affects sweet taste intensity, pleasantness, and preference was recently investigated in a small group of healthy, overweight, middle-aged men and women who all habitually consumed at least 2 sugar-sweetened sodas per day and did not regularly use zero-calorie sweeteners.

The participants were followed for 5 months under free-living conditions with complete control over their diets. Rather than strictly controlling food intake, one of the study authors met individually with each participant to discuss individualized dietary guidelines. The first month served as a baseline period, after which the participants were blindly randomized to a low-sugar or control group for the following 3 months. The low-sugar group was instructed on replacing high-sugar foods with items higher in complex carbohydrates, protein, and/or fats, and to dilute sugary drinks by 50% with water or seltzer so as to continue drinking the same volume. The control group was told to keep doing their thing with minor changes to obtain adequate nutrition. Importantly, both groups were instructed not to replace sugar with zero-calorie sweeteners. During the fifth and final month, both groups could follow any diet they wished.

Ultimately, the dietary advice translated into a 40-50% reduction in sugar intake in the low-sugar group that was evident by the first intervention month (month 2), whereas the control group maintained their sugar intake within 10% of baseline. Amusingly, a sham test was performed monthly to encourage compliance. This involved scanning the thumbs of the participants and telling them that blood sugar levels were being monitored. Apparently, it worked, especially considering that sugar intake began to return to baseline levels by month 5 when the participants could again eat whatever they wanted.

At the end of each month, the participants underwent sensory testing with sweet (vanilla puddings and raspberry beverages) and salty (broth and soda crackers) stimuli that contained varying levels of sucrose and sodium chloride, respectively. The salty stimuli testing was performed to ensure that any changes were limited to sweet taste perception, and the lack of significant findings with regard to salty testing confirms this to be the case.

First and foremost, neither group showed any changes in sucrose detection thresholds (which averaged ~5 grams of sucrose per liter of water), suggesting that reducing sugar intake doesn’t affect the minimum level of sweetness we are able to perceive. Additionally, the low-sugar intervention had no significant impact on the pleasantness ratings for the puddings and beverages, with both groups preferring puddings and beverages that were roughly ~30% and ~13% sucrose by weight, respectively.

Where the significant difference came into play was the perceived intensity of the sweetness. The low-sugar group showed significant increases in their perceived sweetness intensity of the puddings and beverages beginning in month 3, with intensity being about 40% greater than baseline during month 4. However, there was a return towards baseline during month 5, when sugar intake had begun to increase again.

This study suggests that the intensity of sweet taste mimics habitual sugar intake. If you consume a diet lower in sugar, than everything will taste sweeter than it does to someone consuming a diet higher in sugar. From an evolutionary perspective this makes sense. Sugar was not abundant as we evolved and having us perceive foods as sweeter may send a stronger signal to the brain that we should eat whatever this is.

These findings are somewhat in contrast to related research. It has been shown that a 50% reduction in dietary sodium intake for several weeks leads to an increased perceived intensity of salty foods and a reduction in the preferred salt level. This makes sense given that everything tastes saltier. However, in the current study the test foods and beverages were perceived as 40% sweeter on average in the low-sugar group, and yet the participants still preferred the same sucrose concentrations. In essence, it could be argued that the preference for sweetness levels increased by about 40%. How this would influence dietary behaviors remains to be determined.

In addition to the abovementioned salt study, it has been suggested that changes in salt preferences are mediated by salt taste stimulation, as swallowing salt tablets has no effect. In another study, having individuals follow a low-fat diet was shown to lead to a reduction in hedonic ratings for high-fat foods and preferred fat content in foods, but only in the group deprived of sensory exposure to fats. Collectively, these results suggest that it is the sensory exposure in the mouth that influences our dietary preferences. This again makes sense in light of evolution, as it is favorable to prefer foods that are in-line with your habitual diet and to be able to shift preferences when available food changes (e.g., seasonal stuff).

This was a study that needed to be done. Whether or not people can grow accustomed to lower amounts of dietary sugar and be more accepting of lower-sugar foods is an important area of research for public health. It is therefore not surprising that a lot of follow-up work is necessary. Would similar effects be seen with zero-calorie sweeteners? That is, would replacing sugar with a zero-calorie sweetener maintain the perceived intensity of sweet taste? Similarly, would maintaining dietary sugar levels through sugar pills that eliminate the hedonic effects do anything? It would also be nice to have this study replicated from an independent source with a larger sample size.