Temporal trends in the epidemic of childhood obesity have been paralleled by increases in the consumption of sugar-sweetened beverages (SSB) during childhood. Consumption has increased dramatically over the past several decades in all age ranges, with some moderation over the past 10 years. Evidence from cross-sectional, longitudinal, and interventional studies supports links between SSB consumption in childhood and unhealthy weight gain, as well as other untoward health outcomes. These data have stimulated public health efforts to curtail consumption as a means of improving childhood weight status and related health outcomes. Reducing ready access to SSBs, changing the message environment to which children are exposed, and replacing SSBs with healthier beverages have had moderate success in decreasing SSB consumption and curbing unhealthy weight gain.
The current worldwide epidemic of childhood obesity is well documented; childhood obesity in the United States has tripled from the 1970s to 2000, and significant increases have occurred even in developing areas of the world (62, 111). In the United States, current rates of childhood overweight and obesity are 15% and 17%, respectively (110), whereas in Europe, rates vary from 6% to 27% based on the country (150). Equally well documented are the sequelae of childhood obesity, with increased risks of bone and joint problems, sleep disturbance, and psychological problems during childhood and higher risks of cancer, type 2 diabetes, and heart disease in later life (31, 69, 73, 74, 76, 84, 118). Quality of life and well-being may be significantly affected by obesity in individuals around the world. In addition, each year, the United States spends between $150 billion and $190 billion in obesity-related costs, or about 20% of all health care spending (25, 47). As the long-term risks of obesity are discovered, those in the medical and public health communities are increasingly motivated to reduce obesity rates. However, it has been difficult to document the exact causes of this epidemic of childhood overweight and obesity. The search for etiologies has been difficult because the development of childhood obesity is a multifactorial process, and contributors are related largely to common and difficult-to-measure lifestyle factors, including a lower amount of physical activity and an excess of calories ingested (58, 149).
Definitions of Sugar-Sweetened Beverages
A significant consequence of the rise in sugar availability has been the rise in consumption of beverages sweetened with added sugars, frequently referred to as sugar-sweetened beverages (SSBs) (120). SSBs encompass a wide variety of drink types, including sodas/soft drinks, juices with added sugar, Kool-Aid, sport drinks, energy drinks, and sweet tea (44, 90, 107). Trends in increased intake of SSBs are found in children (16, 146), adolescents (104, 152), and adults (27, 35, 119). These have a well-known association with dental caries (98), and research has been increasingly focused on their potential contribution to the obesity epidemic.
Although some studies have reported juice consumption alongside that of SSBs, most studies—as well as this review—consider SSBs separately from juice. Because juice comes from fruits and thus has a small amount of vitamins and a minor amount of fiber, parents may view juice as a more nutritious option (17). Juice bears some similarities to SSBs: First, simple sugar is the only predominant calorie source in juice (though some orange juice preparations have a small amount of protein as well); second, juice consumption, like SSB consumption, has been linked to a decrease in milk consumption (107, 125); and third, juice, like SSBs, has been linked to unhealthy weight gain in some (125, 146) but not all (2, 45, 126, 146) studies. Additional findings have linked juice consumption to shorter stature or poorer linear growth compared to nondrinkers (125, 146), which has not been seen in studies regarding SSBs. Some studies have suggested that juice is a gateway to SSB consumption (129), warranting at least a mention here. In this review, studies considering juice and SSBs together will be specifically noted.
Even without considering 100% juice along with SSBs, the variety of drinks considered as SSBs have varying amounts of added sugar per 12-ounce serving. These range from drinks containing 10 g of sugar, such as light sport drinks, to those containing 51 g, as in orange sodas. The relationship between SSB consumption and health can be a difficult effect to study because the calorie content of each serving size varies on the basis of the amount of sugar. This review considers studies evaluating the health sequelae of SSB consumption in childhood.
Trends in SSB Consumption
In 1977–1978, children in the United States consumed on average 88 kcal per day in SSBs; by 1999–2000, this number had grown to 166 kcal per day (107), as shown in a composite summary of multiple sources in Table 1 (21, 75, 100, 107). This amount has moderated more recently; consumption in recent years has averaged ∼150 kcal daily (52, 75, 100). However, this quantity remains much larger than historical levels (91). In the mid-1990s, children’s intake of sugared beverages passed that of milk (21). At the current rates of consumption, each child in the United States ingests on average a total of 55,000 kcal per year in SSBs. If this amount is above the usual caloric need and not offset by decreased intake or increased metabolism, the result is an unhealthy amount of stored fat tissue. This observation supports the plausibility that SSB consumption may contribute to adverse childhood health on an epidemiologic basis.
SSBs and Unhealthy Body Weight Status
Most of the investigation into SSB consumption has focused on the relationship with unhealthy weight status, including a higher body mass index (BMI) and a higher amount of adipose tissue compared to nondrinkers. Our understanding of these connections has been informed through the use of multiple approaches that we now consider here in the order of increasing strength of the study designs involved.
Cross-sectional studies examining the relationship between SSB consumption and weight status cannot determine causality but may provide useful information on relationships. Results from efforts to determine cross-sectional relationships have been mixed, although direct associations have been noted in multiple age groups (96).
Ariza et al. (5) found both that Hispanic American children ages 5–6 years who drank SSBs had an odds ratio (OR) of obesity of 3.7 and that overweight children in the cohort were more likely to be SSB drinkers. In an analysis of 8,500 US preschool children, using linear regression we found significant relationships between the number of servings of SSBs and the BMI z-score of the children at both 4 and 5 years of age (32), as well as higher odds of overweight (at age 4) and obesity (at age 5) even after adjustment for confounding variables, including sex, SES, and race/ethnicity. In a wider age group, Grimes et al. (60) found in a large cohort of Australian children ages 2–16 years that those drinking SSBs were more likely to be overweight. Nicklas et al. (106) evaluated children from the Bogalusa Heart Study at age 10 years and found an OR for overweight of 1.33 for SSB drinkers versus nondrinkers. Berkey et al. (12) found in 9-year-old and 14-year-old girls (but not boys) a linear relationship between the amount of SSBs consumed and BMI.
Nevertheless, not all cross-sectional studies have demonstrated these relationships. Among younger children, O’Connor et al. (109) evaluated data from 1,160 children ages 2–5 years in the 1999–2003 NHANES and found that even though children drinking >12 ounces daily of SSB had higher total daily caloric intake, their BMIs were similar as seen in nondrinkers. Keller et al. (71) noted that among a small cohort of children ages 3–7 years, those drinking SSB were not more likely to have a higher BMI. Forshee et al. (54) did not find any difference in BMI according to SSB intake in a large cohort of children ages 6–19 years. Although it is not mentioned in these reports, the potential for errors in reported caloric intake is a possible explanation for these findings.
The potential for SSBs to affect weight depends on whether consumption of calories from SSBs is above an individual’s usual caloric intake (and is not offset by a compensatory decrease in intake of calories from other sources or by an increase in energy expenditure). Increased consumption beyond energy expenditure would be expected to result in weight gain. O’Connor et al. (109) determined that children who drank >12 ounces daily of SSBs had a higher total daily caloric intake than did nondrinkers; however, total energy expenditure was not assessed. Other studies found that children who drank SSBs were less likely to drink milk than were those who did not drink SSBs, which suggests a compensatory decrease in another calorie source, as well (32, 71, 89). However, changes in consumption of healthier sources of calories also highlight the potential for other mechanisms of untoward health effects of SSBs, such as the potential for a lower intake of protein and calcium among SSB drinkers if milk intake were to decrease.
Longitudinal study designs have the advantage over cross-sectional studies in that they can potentially identify associations between SSB consumption and changes in weight status over time, although as with cross-sectional studies, confounding effects of unmeasured or unaccounted for variables that affect both SSB consumption and unhealthy weight gain cannot be ruled out. As with cross-sectional studies, longitudinal studies have had mixed results regarding change in weight over time in association with SSB intake.