Has the World Become Too Sweet?

While the use of added sugars and the discovery of chemicals that impart a sweet taste with few or no calories are relatively recent phenomena in human dietary history, our attraction to sweet taste is not. With industrialization came technological improvements and new sources of sweeteners—both nutritive and nonnutritive—that led to increased availability and lowered costs to meet the increasing demands for sweets. Added sugar, in its many forms, tastes good, which in turn contributes to its enduring popularity and contribution of more than 10% of daily calories to the US diet among adults and an even larger percentage (16%) among children. By the age of 2 years, on any given day, an American is more likely to eat a manufactured sweet than a fruit or vegetable.¹ The more added sugar in a child’s diet, the fewer fruits and vegetables.² The “sweetness” of the food environment in which children live continues to evolve, with increasing numbers of foods, beverages, and liquid medications that are sweetened with nutritive sweeteners, nonnutritive sweeteners (NNS), or blends of both.³

As discussed in the American Heart Association’s scientific statement “Added Sugars and Cardiovascular Disease Risk in Children,” by Vos et al,⁴ the effects of a diet rich in added sugars observed in children are similar to effects observed in adults. Though the strength of the evidence varies depending on the particular risk factor and the availability of clinical trial data, the direction is clear: Added sugars are associated with obesity, blood pressure elevations, and other metabolic effects. Vos et al resisted the urge to oversimplify the nutritional issues related to added sugars. Their calculated, evidence-based approach to understanding the impact of added sugars on children’s diets leads to an inescapable conclusion: Added sugars in the diet, particularly as beverages, add to cardiovascular risk. Vos et al recommended that children younger than 2 years consume no added sugars and older-aged children consume no more than 25 g (5-6 teaspoons) per day, which is about half the current consumption rates for 4-to-18 year olds.

Missing from this scientific statement is a discussion of why we have a problem with overconsumption of added sugars during childhood (and beyond), as well as the problems associated with substitution of NNS for added sugars and the prospects for altering dietary patterns in the current food environment. The answers begin with our biology. Evolution has shaped the taste of foods that children initially prefer or reject—in an environment with limited nutrients and abundant poisonous plants, sensory systems evolved to detect and reject perceptions that specified potential poisons that taste bitter and to prefer perceptions that specify crucial nutrients such as the once rare energy (carbohydrate)-rich plants that taste sweet.^5,6 The child does not need to be “introduced to” added sugars to be attracted to sweet taste. In fact, the preference for the taste of sweet is inborn, attracting newborns to the predominant taste quality of what once was their only first food—their mother’s milk. The preference for sweet tastes remains heightened throughout all of childhood, attracting children to sources of calories (most likely fruits) during periods of maximal growth.^7,8 For children especially, sweet taste can provide pleasure and blunt expressions of pain,^9,10 and is an integral part of modern cuisine. Sweet tastes can mask the bad tastes¹¹ that are inherent in a food or which develop during processing. The same receptors that detect sugars in the mouth are also found in the gut,¹² perhaps warning the digestive system of impeding nutrients.

But as with other human behaviors, experience teaches children the rules of cuisine, including how sweet a food should taste. The sensation of sweetness is context dependent and can acquire meaning through associative learning.^13,14 Through familiarization and repeated exposure, children develop a sense of what should, or should not, taste sweet. Early introduction to sugar-sweetened beverages not only is associated with increased likelihood of consuming sugar-sweetened beverages¹⁵ but also results in heightened sweet preferences several years later.¹⁶ In other words, children learn from an early age to like what they are exposed to, as well as what should (in the sense of expectation) and should not taste sweet. Food habits are established by 2 years of age1,^17-19—if “we are what we eat,” then what a child eats during early life is what the child will become.

While this “sweet” attraction may have served children well in a feast-or-famine setting, today it makes them vulnerable to food environments abundant in processed foods rich in added sugars and NNS and poor in healthy sweet foods like fruits.^20,21 Now, in many parts of the world, a mismatch exists between children’s physiology and their current²² food environment: Many live in an environment that provides food everywhere—it is inexpensive, good tasting, and served in large portions. Children’s natural taste predispositions them to be drawn to processed foods that taste sweet, which in turn makes them especially vulnerable to poor food choices. Sweetened processed foods and beverages are displacing the very foods—fruits—that our taste system evolved to be attracted to. Eating processed foods that are highly sweetened and predictable in taste does not familiarize children to the varying tastes and textures of fresh, whole fruits, important sources of cardio- and metabolic-protective nutrients, including potassium, fiber, and antioxidants,^23-27 that are part of a healthy diet for children and adults.

Vos et al take an extra step beyond establishing the relationship of added sugars to cardiovascular risk, suggesting additional mechanisms of impact and harm. Foods with added sugars, often nutrient poor, don’t just conflict with foods that are nutrient rich²⁸—they displace calories because they are more preferred by the child. To suggest that the lower intake of vegetables when children eat a “combo meal” of sweetened punch drink and carrots/red peppers compared with a combo meal of water and carrots/red peppers is caused by a conflict in taste fails to acknowledge the amount of calories coming from the punch (~90 calories) compared with the minimal amounts (<10 calories) from the vegetables consumed by these children. The evidence shows that children are particularly vulnerable to over-consuming processed foods and sugar-sweetened beverages, important and independent causal factors in the childhood obesity epidemic. The increased levels of sugar in the punch cater to children’s natural taste predispositions. We should be asking why is it culturally acceptable that a sweetened beverage, whether nutritive or nonnutritive, constitutes an appropriate component of a meal for children (see de Ruyter et al ²⁹)? Shouldn’t these beverages be treated as a dessert, offered only occasionally and not during the main meal?

Attempts to limit consumption of sweet-tasting foods and beverages may be more difficult for some children because of the individual differences in the inherent hedonic value of sweet taste³⁰ and how sweets make them feel.10 The frequency with which the child is exposed to such foods and their salience within a given cultural framework are also driven by multiple aspects of availability, food marketing and their interplay with extant cultural beliefs, preferences, and norms.³¹ This emphasizes the need for strategies to alter the current patterns of exposure to sweetened foods, particularly for children, all of whom are vulnerable, some more than others, and the need to direct children’s proclivity for sweets toward healthy, good-tasting fruits.

Is the answer just to replace added sugars with NNS? Get rid of the calories but provide sweetness because children like to eat or drink foods and beverages that taste sweet? The American Heart Association scientific statement on nonnutritive sweeteners was cautious about the role of these agents in weight management for adults.²² We believe that the pediatric clinical trial evidence is inadequate to make the claim that the use of NNS is beneficial. Using NNS perpetuates the highly sweetened food environment. The randomized trial data cited in Vos et al on the effects of replacing a sugar-sweetened beverage with a NNS-sweetened beverage on body weight includes mostly normal-weight children,^29,32 without an appropriate control group (no unsweetened beverage such as water was included). Prior trials have shown inconsistent outcomes, including some that show an association of NNS-sweetened beverages with weight gain and increased risk for cardiovascular and other diseases (see references^33-35 for review). As stated by Vos et al, the possibility that NNS, in some conditions, may be metabolically active cannot be discounted³⁶ and requires scientific study. Furthermore, although replacing nutritive sweeteners with NNS reduces the caloric content, experience nonetheless teaches children that those particular foods and beverages should taste sweet. Future trials should not include foods or beverages with NNS as the sole control group, and psychophysical taste measurements should be included to determine whether the intervention modifies the liking for sweets, since taste is one of the most important determinants of what young children choose to eat.³⁷

The gaps in knowledge regarding effective ways to reduce added sugar consumption are huge. There is no evidence that the biologic sweet preference can be lowered in children. Research is needed to determine whether gradually taking added sugars and NNS out of children’s diets, as has been suggested for salt³⁸ (another taste highly preferred by children8), leads to preferences for lower levels of sweetness. That food habits are established by 2 years of age,1,^17-19 and that added sugar intake among many women of childbearing age remains at levels well above current recommendations,^39-41 highlights the relevance of focusing not just on children but on entire families. Parents feed their children the foods they themselves like and serve as models of eating that children learn to emulate.⁴² Furthermore, sweetened foods are often inexpensive, marketed as normative food choices, and more likely to be available in the home than are fruits and vegetables. Research is needed to determine the impact of subsidies for healthy foods (e.g., fruits, vegetables) and taxation on foods with added sweeteners; some communities have begun to adopt such taxes.⁴³

The societal and clinical impact in promoting sustainable food habits is significant since what a child eats determines in part what the child becomes.^18,44,45 How can we as a society create public awareness promoting healthy, sustainable food habits for all Americans? The evidence compelling us to accomplish this goal exists in our children and future generations.