How growing up sweet can turn sour

Today's infants and children are growing up in a much sweeter nutritional environment than previous generations. Negotiating added sweeteners, sugary beverages and sweet snack foods has become an important daily task in bringing up today's children. Even though sugary beverage consumption, which contributes the most to this phenomenon, is declining at least in the United States (1,2), there is no denying the generational shift in the nutritional landscape of children who are now growing up with much greater access and exposure to sweeter foods and beverages. As summarized in this issue (3), analysis of the food supply in the United States shows that >70% of foods contain sugar, and consumption of soft drinks, including juices, has increased fivefold since 1950 (4), and studies from across the globe not presented in this issue show sugary beverage consumption is rising very rapidly (5–8). This sweeter environment includes not just an increase in ordinary table sugar (sucrose), but a whole host of other alternative natural and artificial sweeteners that are appearing in the food supply, some of which are likely to have important consequences on growth and development relevant to obesity and associated disease risk that could be distinctly different from sucrose. While much research has been done to examine the ‘sweeter’ food environment and its effects on obesity and disease risk in general, much less research has considered how this phenomenon specifically affects growth and development of infants and children. In this special issue, we present a series of new work that focuses on this problem as it relates to paediatric populations. The accompanying editorial by Bray and Popkin presents an update on an important hypothesis that these authors proposed 10 years ago (9). In their landmark paper, they discussed the impact of the appearance of high-fructose corn syrup (HFCS) in the food supply as a potential contributor to the obesity epidemic (10). Since this earlier publication, a new body of science has emerged and established the evidence for strong links between dietary sugars, especially fructose, and obesity and metabolic risk, including fatty liver disease, which notably has more than doubled in children in the last 10 years (11). Greater fructose consumption in adolescents has been shown to be associated with cardiometabolic risk and this is mediated through effects on increasing visceral adiposity (12). These findings suggest that greater exposure to fructose also probably contributes to the rise in paediatric fatty liver disease that is occurring (11), although specific data supporting this link have not yet been analysed. A new review by Stanhope et al. outlines how metabolism of the fructose moiety of sucrose explains many of these adverse metabolic effects (13). These effects are likely to be worse during growth and development because fructose promotes adipose tissue differentiation during growth (14). In support of this concept, the paper in this special issue by Disse et al. shows that children with fructose malabsorption have lower levels of obesity (15). Although not definitive, because this finding may also be explained by ‘loss of calories’ or effects of fructose in the gastrointestinal system promoting gut flora that would protect against obesity, this finding supports the concept of a more damaging effect of fructose on obesity during growth, and merits further investigation that should also include stronger measures of body composition/fat distribution and metabolic outcomes. Also, in this issue, Morgan presents results of a systematic literature review on the links between HFCS and obesity in children (16). This analysis yielded mixed results with some studies showing an effect and others showing null effects. However, the number and quality of studies in this area are very limited and remain focused on body weight, rather than body fat distribution and metabolic risk as outcomes, and have not considered the increased fructose exposure that comes from fruit juices. For example, the impact of a shift towards use of HFCS and greater fruit juice consumption should be examined in the context of the estimated doubling of fatty liver disease among US children and adolescents that was recently reported (11). Although some would argue that the overall consumption of sugar and fructose have declined in recent years (a trend found only at most in a few countries but not globally), it is important to point out that levels are still higher from a generational perspective, and that much of the world is experiencing major increases in sugar intake and hence fructose