Adults who spent six months eating diets deliberately high, low, or average in sweetness ended the trial liking sweet tastes about as much as they had at the start, according to a randomized controlled trial that tested a widely repeated assumption behind public health advice.
The Sweet Tooth Trial, conducted by researchers at Wageningen University and Research in the Netherlands and Bournemouth University in the United Kingdom, assigned 180 healthy adults to three groups. The results appeared in the American Journal of Clinical Nutrition and have circulated repeatedly through science news outlets since.
The finding is a null result, and interpreting one correctly requires a specific kind of care. It does not establish that dietary sweetness can never affect cravings. It establishes that this trial, at this size, over this duration, in this population, did not detect a difference.
The Design and What Was Measured
Participants were randomly assigned to a low-sweetness diet, a regular-sweetness diet serving as the control, or a high-sweetness diet, with roughly 60 people in each arm. The trial used partial food provision, supplying about half of each participant's daily energy needs rather than all of it. In the low arm, 7% of provided foods and beverages were sweet-tasting; in the regular arm, 35%; in the high arm, 80%.
The sweetness in the provided foods came from a combination of sugars, low-calorie sweeteners, fruits, and dairy. That mixture is central to how the results should be read, because the trial manipulated sweet taste rather than sugar content specifically.
The primary outcome was liking for sweet taste. Secondary outcomes covered taste intensity perception, food choice and intake, food cravings, dietary patterns, body composition, body weight and related markers.
Across those measures, the researchers reported no meaningful differences between groups. Sweet taste liking did not change. Neither did energy intake or body weight. Assessment visits continued after the intervention period, at months 7 and 10, allowing the researchers to observe what happened once the provided food stopped.
Reading a Null Result Without Overreaching
A study that finds no difference is not the same as a study that proves no difference exists. The distinction turns on statistical power, duration, and population.
With roughly 60 people per arm over six months, the trial was designed to detect effects of a certain size. A smaller effect could exist and go undetected. Six months is also short relative to how long taste preferences form, which begins in childhood and develops over years, so an intervention in adulthood may be working against a preference already largely set.
Partial food provision means participants controlled part of their diet, which reflects real life more closely than a fully controlled feeding study but introduces variability in how completely each person followed their assignment.
The population matters as well. Participants were healthy adults with an average age of about 35 and an average body mass index of about 23, meaning most were not living with overweight or obesity. The results cannot be extended to children whose taste preferences are still forming, which is where much sweetness-focused public health advice is directed. The researchers have said they would like to repeat the study in children for that reason.
The Conclusion the Authors Draw from It
Katherine Appleton, a professor in psychology at Bournemouth University and corresponding author, framed the finding as a challenge to a specific piece of guidance.
"People have a natural love of sweet taste which has led many organizations, including the World Health Organization, to offer dietary advice on reducing the amount of sweetness in our diets altogether," Appleton said. "However, our results do not support this advice, which does not consider whether the sweet taste comes from sugar, low-calorie sweeteners, or natural sources."
Kees de Graaf, a professor in sensory science and eating behavior at Wageningen University, said the trial fills a specific gap. "Most studies examining the effects of repeated exposure to sweet taste on the liking, or preference, for sweetness have been short-term, covering periods up to one day," he said. "Some people avoid sweet-tasting foods, believing that regular exposure will increase their preference for sweetness, but our results show that's not the case."
The Boundaries of This Finding
This trial does not say sugar is fine. It says sweet taste and sugar content are different variables, and that manipulating the first did not change the measured outcomes.
The evidence linking added sugar intake to dental caries, and high-calorie diets to weight gain and metabolic disease, is separate and was not tested here. A diet can be low in sweetness, and high in calories, or sweet and nutritionally sound, and the trial's design deliberately separated those dimensions.
The trial also did not examine low-calorie sweeteners as a distinct question. Because sweetness in the provided foods came from a mix of sources, the results cannot answer whether sweeteners specifically help or hinder anything.
Funding deserves attention. The project was co-funded by a Dutch government public-private partnership allowance and also received private contributions from the American Beverage Association, the International Sweeteners Association, Unilever, Cargill, DSM-Firmenich, Arla Foods and several other food and ingredient companies. The published paper states that private partners sat on an advisory committee giving nonbinding advice, while an independent steering committee gave binding advice before, during and after the trial. Readers weighing a finding that runs against advice to reduce sweetness should know who helped pay for it.
Nothing here changes clinical or public health guidance, and a single trial would not be expected to. What it adds is evidence that one specific assumption, that reducing exposure to sweet taste retrains preference, did not hold under these conditions.
Anyone making dietary changes for a medical reason, including diabetes management or weight concerns, should work with a clinician or registered dietitian rather than adjusting based on a single study. Readers with a history of disordered eating should be particularly cautious about restructuring their eating around any single research finding. MedicalDaily has covered other nutrition trials whose results resisted the expected story.
Key Questions Answered
What did the trial test? Whether changing how much sweet-tasting food people eat changes how much they like sweetness. It assigned 180 healthy adults to low, regular or high dietary sweetness diets for six months, providing about half their daily energy needs.
What did it find? No meaningful differences between groups in sweet taste liking, energy intake or body weight.
Does this prove sweetness does not affect cravings? No. A null result means this trial, at roughly 60 people per group over six months in adults, did not detect a difference. A smaller effect could exist, and results may differ in children whose preferences are still forming.
Does this mean sugar is not a problem? No. The trial manipulated sweet taste, not sugar content specifically, using a mix of sugars, natural sweetness and low-calorie sweeteners. Evidence linking added sugar to dental caries and high-calorie diets to metabolic disease was not tested here.
Who funded it? A Dutch government public-private partnership allowance, plus private contributions from food, beverage and sweetener companies including the American Beverage Association and the International Sweeteners Association. An independent steering committee gave binding advice on the trial.
Does this settle the debate on low-calorie sweeteners? No. Sweetness in the provided foods came from multiple sources combined, so the trial cannot isolate the effect of sweeteners specifically.
Should anyone change their diet based on this? Clinical and public health guidance has not changed. Anyone making dietary changes for a medical reason should work with a clinician or registered dietitian.
