What do we know about sweetness preference?

Science news from the EFAD Conference 2018

Highlights:

• Human preference for sweet taste is innate and universal. Liking for sweetness is intense during childhood and decreases to adolescence and into adulthood, but our appetite for sweetness remains until old age.
• Current evidence doesn’t support the notion that exposure to sweetness can lead to habituation to, or increased preference for, sweet taste.
• A higher sweet taste exposure, including from foods containing low calorie sweeteners, tends to lead to reduced preferences for sweetness in the shorter term

Sweet taste is universally liked. Human appetite for sweetness is innate, expressed even before birth, and spans across all ages and cultures around the world. At the same time, there is also a clear public health mandate to limit the overconsumption of free sugars in the diet. While the need to reduce excess sugars intake is well established, evidence does not support the need to reduce overall sweet taste in the diet on the basis of theories suggesting that by reducing exposure to sweet taste we could potentially change our preference for sweet food. In this context, the impact of exposure to sweetness on preferences, food intake and ultimately on body weight is an interesting topic of discussion among experts.

The role of sweet taste exposure in preference for sweetness was among the “hot topics in obesity and diabetes” that were discussed in a session at the European Federation of the Associations of Dietitians (EFAD) Conference 2018 that took place in Rotterdam, Netherlands, from 28th to 29th September. Prof Katherine Appleton from Bournemouth University (UK) presented the conclusions of a recent systematic review of the literature on this research field that was published in the American Journal of Clinical Nutrition in March 2018.

How does exposure to sweet taste influence preference and food intake?

Current evidence doesn’t support the notion that exposure to sweetness can lead to habituation to, or increased preference for, sweet taste or that by reducing exposure to sweet taste we could change our future preference for, or reduce intake of, sweet food. This was one of the key conclusions of the systematic review by Appleton et al. (2018) that was presented at the EFAD Conference. Reviewing the available evidence about the impact of dietary exposure to sweetness on the generalized acceptance, preference, choice, and/or intake of sweet taste in the human diet, Katherine Appleton and her colleagues examined 21 studies that met the criteria of their systematic review. The researchers concluded that the evidence from controlled clinical trials suggests that a higher sweet taste exposure tends to lead to reduced preferences for sweetness in the shorter term. This sensory-specific satiety has been previously described and suggests that exposure to a particular sensory attribute (e.g., sweetness) can lead to reductions in the apparent pleasantness and choice of foods and beverages with that same attribute, relative to others (Rolls, 1986). Thus, for example, exposure to sweet taste from dietary sources with low amounts of sugars, sweetened with low calorie sweeteners, may not only replace consumption of free sugars but could also reduce the desire for sweetness from other sources in the short term.

While this effect has been studied extensively in short-term trials, there are limited data from longer term studies. In any case, neither the available long-term clinical trials, nor the observational studies which show equivocal evidence, support public health and nutrition policies that call for a reduction of low calorie sweeteners’ use in the context of an overall reduction of sweetness and on the basis of a potential negative effect on habituation to sweet taste (sustained “sweet tooth”). Similarly, a review of the literature by Public Health England in the UK (2015) concluded that there is little evidence for the theory that repeated exposure to sweetness can lead to habituation to sweet taste.

Facts about sweetness preference

Human appetite for sweetness is innate, expressed even before birth, and spans across all ages and cultures around the world, which makes sweetness an integral part of the human diet. Liking for sweetness is intense during childhood, which may reflect the nutritional need for attracting young organisms to foods that are high in energy during periods of maximal growth (Mennella et al, 2014). Our natural liking for sweetness remains until old age, however, there is evidence that it decreases from childhood to adolescence and into adulthood (de Graaf and Zandstra, 1999).

While all humans express the same response to sweetness immediately after birth, the liking for sweet products changes over time and becomes highly idiosyncratic in adults (Schwartz et al, 2009). An appetite for sweetness is present in most adults, although large inter-individual differences exist in both the preferred level of sweetness in familiar products and in the range of foods and drinks that are consumed sweet (Bachmanov et al, 2011). There is also evidence that genetic differences among people may partly account for individual differences in sweetness preference and in the consumption of sweet foods and drinks (Keskitalo et al, 2007; Joseph et al, 2016).