Sweet Tooth: Nature or Nurture? Assessing the role of dietary sweetness exposure on sweet taste liking

Humans have an innate preference for sweet taste, often leading to concerns about energy overconsumption. This preference underlies a widely accepted public health narrative: greater exposure to sweetness makes it more liked, leading to higher sugar intake, elevated calorie consumption, and, ultimately, weight gain. However, the empirical data for this causal link remain limited. This thesis investigates whether long-term exposure to high and low dietary sweetness alters sweet taste preference, sweet taste perception, food intake, and body weight in healthy Dutch adults. The first part of the thesis describes the study design of a six-month randomized controlled trial with a four-month follow-up (the Sweet Tooth study). The intervention used a whole-diet approach, assigning 180 healthy adults to one of three dietary groups differing in sweet taste exposure: low (10–15% energy from sweet-tasting foods), regular (25–30%), and high (40–45%). Sweetness exposure was manipulated through a variety of sugar-sweetened, low-calorie-sweetened, and non-sweet foods and beverages, while maintaining similar energy and macronutrient profiles across groups. The second part of the thesis focuses on the development of sensitive and reliable methodologies to measure sweet taste preference, liking, and perception. A method called Ranking on a Scale was evaluated across several experiments. This method, which combines ranking and rating, effectively captured individual differences in hedonic responses to sweetness across diverse food types, including familiar and unfamiliar, sweet and non-sweet items. In the third part, cross-sectional analyses explore the relationship between sweet taste liking and intake of sweet foods using baseline data from the Sweet Tooth study. Sweet taste liking was assessed using multiple measures, including psychohedonic functions, sweet liker phenotypes, and self-reported preferences. While different sweet taste liking measures were in agreement, only self-reported preferences were associated with sugar and sweet food intake, challenging the assumption that hedonic response alone directly predicts consumption of sugar and sweet food. Finally, the fourth part presents the main findings of the randomized controlled trial. Over the six-month intervention and four-month follow-up, no significant effects of dietary sweet taste exposure were observed on sweet taste preference, sweet taste perception, food intake, or body weight. These findings suggest that modifying exposure to sweet-tasting foods over six months alone is insufficient to shift taste preferences, affect food intake and body weight. In conclusion, this thesis provides one of the first comprehensive assessments of long-term sweet taste exposure using a whole-diet, randomized controlled approach. The findings offer valuable insights that should be considered when formulating public health recommendations. They challenge the assumption that simply reducing the number of sweet-tasting foods will automatically change preferences and intake. This highlights the need for additional research on the mechanisms underlying sweetness preference formation, its health implications, and the development of strategies to promote healthier food behaviors.