Excessive Fruit Juice Consumption: How Can Something That Causes Failure to Thrive be Associated with Obesity?
Excess Fruit Juice Consumption by Preschool-Aged Children is Associated with Short Stature and Obesity. Dennison BA, Rockwell HL, Baker SL. Pediatrics 1997;99:15-22.
Summary: What are the effects of excessive fruit juice consumption in childhood? This article looks at the association of fruit juice intake with height, weight, and weight-for-height measures in preschoolers. Subjects were 2- and 5-year-old children presenting for well child care to a general primary care practice. They were recruited from 225 subjects as part of a study to evaluate methods of measuring dietary fat intake. Data were derived from a written record of the child's intake for 7 consecutive days. The record was provided by the parent or caregiver, following instructions from a nutritionist who provided visual aids for estimating portion size. Measures of height and weight were also collected along with demographic information, parental self-reports of height and weight, and the child's activity level.
One hundred sixty-eight of the 225 eligible subjects (75%) returned an adequate 7-day food record. Parents who completed the food record were better educated than parents who did not. They were also less likely to smoke or to receive food assistance. There were no measured differences between children whose parents did or did not complete the food record. Ninetyseven percent of the study population were white.
Excess juice consumption was defined as ≥12 ounces per day, a figure twice the mean and three times the median for the entire study population. Two indices were used to determine obesity: the body mass index or BMI (weight in kg/height in meters2) and ponderal index (weight in kg/height in meters3). Subjects with a BMI ≥75th percentile for age and gender (by national norms) or a ponderal index ≥90th percentile (by distribution within the study) were considered very obese. Short stature was defined as height <20th percentile for age and gender.
Nineteen children (11%) consumed ≥12 ounces fruit juice per day. Of these, 8 (42%) had short stature compared with 21 (14%) children whose fruit juice consumption was <12 ounces per day. In addition, 10 of the 19 children defined as excessive juice drinkers (53%) were obese compared with 47 of the 149 who were not excessive juice drinkers (32%). Statistical adjustment revealed that the excessive juice drinkers who were short were not also obese; these were two separate populations. Statistical adjustments for maternal height, child age, child sex, and age-sex interaction strengthened the associations of excessive fruit juice consumption with both short stature and obesity.
Comment: Fruit juice is a popular choice for preschoolers. Children like its sweet taste and parents believe it to be healthy and nutritious, despite the fact that it has been linked to dental caries and gastrointestinal symptoms. In a study examining dietary patterns in infants and toddlers with failure to thrive, Smith and Lifshitz (Pediatrics 1994;93:438-43) reported excessive fruit juice consumption in eight patients whose growth improved when juice intake was decreased. This showed plainly what nutritionists and pediatricians were warning the public about: that juice could cause malabsorption and could displace other nutrients in the diet.
The current paper by Dennison, Rockwell, and Baker is novel in that it examines the effects of high levels of juice consumption in children in the general pediatric population, not in a clinic referral group. What they found were two different nutritional problems. Like Smith and Lifshitz, they found a group whose excessive intake was having a negative effect on their growth, in this case producing short stature. But they also found a group in whom high juice intake was associated with obesity, clearly the opposite of failure to thrive.
How can excessive fruit juice consumption produce two such opposite effects? Or, more specifically, how can high juice consumption be associated with obesity? The key is in the word “associated.” The argument for causation is much stronger for the putative role of juice in failure to thrive. This argument is supported by a biological mechanism (carbohydrate malabsorption), experimental evidence (improvement in growth with reduction in juice intake), and consistency across the literature (numerous papers have found juice intake to produce malabsorption and associated symptomatology, e.g., Pediatrics 1988; 82:64-8, J Pediatr 1992;120:85-29). Turning to obesity, the argument for causation is not nearly as compelling. However, the association in this study may be real, that is to say that obese children may indeed have consumed more juice than their nonobese counterparts. This may be because the obese children overconsumed in general and that juice was just one component of an overabundant diet. However, in this study the total caloric consumption of these children was not significantly different (by most measures) than that of their peers. Another explanation might be the parents' attempt to correct their child's obesity. Perceiving juice to be nutritious, parents may have encouraged juice consumption in order to improve the child's diet. This association could be an artifact of the study itself. It is not clear whether anthropometric data were collected before or after dietary intake data. However, simply knowing that weight status measures were going to be collected might have made the parents of heavier children attempt to change their child's diet to one they perceived to be more healthy.
It is disappointing that the study did not examine parental beliefs and attitudes toward juice drinking. Many parents may believe that juice should be promoted as part of a balanced diet. In this study, it is impossible to say whether high juice intake caused obesity or whether knowing the child was obese caused parents to encourage high juice intake. Clearly, physicians should be more specific about juice consumption when advising patients to increase their intake of fruit and vegetables. Because juice is sweet and children like it, it may be perceived by parents as an easy way to get children to improve their nutrition.
Amy A. Levine
Department of Nutrition; University of North Carolina at Chapel Hill; Chapel Hill; North Carolina, U.S.A.