The trick to temper your sweet tooth by temporarily cutting down on sugar and sweeteners does not seem to work after all. A large-scale Wageningen study shows that people who followed a low-sweetness diet for six months remained just as fond of sweet flavours as before. Those who consumed extra-sweet foods did not grow to like sweet flavours more. 'Our sweet taste preference turns out to be more stubborn than thought,' concludes PhD student Eva Čad.
The internet is full of tips for 'resetting' your preference for sweetness: avoid sweet foods and drinks, and supposedly your cravings for sugary treats will fade. But scientific evidence for this is scarce. Therefore, Čad designed a long-term intervention study involving 180 participants. Over six months, they received home-delivered breakfasts, lunches and snacks containing either a high, low or an average amount of sweet products. These included products sweetened with sugar and sweeteners. For example, the low-sweetness group received plain yoghurt and savoury pepper spreads, while the high-sweetness group got fruity yoghurt and sweetened peanut butter. The moderate group had a mix of both.
Firmly rooted
Before, during and after the study, participants took part in detailed taste tests involving products such as cake, custard and lemonade, each offered in five sweetness levels: from barely sweet to extremely sweet. The researchers asked how much the participants liked the products and how sweet they perceived them to be. Those ratings hardly changed throughout the study, regardless of diet. "I expected preferences to shift," says Čad. "That people who ate sweeter foods would grow to like sweeter products more, and vice versa. But that is not what we saw."
Our study shows that this is unlikely to be an effective public health strategy
The results suggest that our preference for sweetness is firmly rooted. It cannot easily be altered through six months of dietary change, at least not in adults. "The idea was that if you eat less sweet food, you will start liking it less and therefore consume less sugar, and thus fewer calories," says Monica Mars, Associate Professor of Human Nutrition and Health. Even authoritative organisations promote this statement as a possible solution to obesity or overconsumption. "Our study shows that this is unlikely to be an effective public health strategy. We need to focus on dietary guidelines that are evidence based." If individuals have little control over their taste preferences, then perhaps more responsibility lies with the wider environment - such as the food industry.
Tightly controlled study
The study was designed to be as fair as possible. Each group had an equal mix of men and women, as well as sweet-liking individuals and on average they had similar ages and BMI. Importantly, participants were unaware of the study's aim. Since meals were delivered to their homes, they could not compare products with one another.
Participantsreceived detailed instructions on what to eat on which days but were free to decide how much they ate. They recorded this in food diaries and had regular contact with a dietitian. This allowed the researchers to closely monitor compliance. Urine samples confirmed that the participants indeed consumed the sweeteners in the products. "That gave us confidence that participants were truly eating the provided foods," says Čad.
Eva Marija Čad will defend her PhD thesis on this research on Friday 13 June at Wageningen University & Research (Division of Human Nutrition and Health).
