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To determine the possible association between carbonated beverage consumption and bone fractures among teenaged girls given the awareness of the concern about the impact of carbonated beverage consumption on children's health.
An urban high school.
A cross-sectional (retrospective) study. Four hundred sixty 9th- and 10th-grade girls attending the high school participated in this study by completing a self-administered questionnaire relating to their physical activities and personal and behavioral practices. The school system and the Harvard School of Public Health Institutional Review Boards approved the study. The girls' self-reports on physical activity, carbonated beverage consumption, and bone fractures are analyzed.
In the total sample, carbonated beverage consumption and bone fractures are associated: odds ratio=3.14 (95% confidence limit, 1.45, 6.78), P=.004. Among physically active girls, the cola beverages, in particular, are highly associated with bone fractures: odds ratio=4.94 (95% confidence limit, 1.79, 13.62), P=.002.
The results reported confirm previous findings, but the mechanism by which cola drinks are associated with bone fractures in physically active girls has neither been fully explored nor determined. Nevertheless, national concern and alarm about the health impact of carbonated beverage consumption on teenaged girls is supported by the findings of this study. The results have policy implications for improving the dietary practices and health of children.
ALARMED BY the fact that "teens drink breathtaking quantities of soda,"1 the Center for Science in the Public Interest in a letter to the Secretary of Health and Human Services urged that department to commission a study on the health impact of soda pop. This article herein confirms an earlier finding of an association between carbonated beverage consumption and bone fractures among teenaged girls, and particularly the association of cola drinks and bone fractures among physically active teenaged girls.2
The study was conducted in an urban high school. Permission to carry out the study was granted by the school system's authorities and also approved by the Harvard School of Public Health's Human Subjects Committee, Boston, Mass.
Data were obtained in the course of a project designed to reduce the incidence of teenaged pregnancy by enrolling girls attending an urban high school in group physical activity programs. Permission from the school was obtained to distribute a questionnaire to 9th- and 10th-grade girls during the school day; approval was granted by the Human Subjects Committees of the school authorities and of the Harvard School of Public Health. Four hundred sixty teenaged girls completed the questionnaire.
The questionnaires were self-administered in a classroom setting and monitored by classroom personnel. Since the responses were confidential, they were not examined by school personnel. However the girls were instructed about the need to answer as best they could and to provide complete answers. The information provided had internal consistency and face validity, although as in any questionnaire, a few questions were unanswered or incompletely answered.
The questions relevant to this article relate to the intensity of the girl's activity level, based on a 5-point scale: inactive, light, moderate, high-level, and vigorous; their medical history; and their carbonated beverage consumption. In particular, participants were asked whether they had ever been told by a physician that they had a bone fracture, and if so, the type or site of the fracture and the year of its occurrence. Questions on carbonated beverage consumption were: "Do you drink carbonated beverages at present? yes/no"; "What type(s) of these beverages do you most commonly consume, ie, diet cola, cola with sugar, other diet carbonated drinks, other carbonated drinks with sugar?"
In addition to questions about physical activity, bone fractures and other questions relating to medical history, and carbonated beverage consumption, behavioral practices were asked about. The areas of inquiry were as follows: (1) current height and weight; satisfaction with present body weight, weight gained or lost (if >2.3 kg) in the past year; being on a special diet for weight loss or gain, vegetarian concerns, low cholesterol, low salt, low fat, or other special dietary reasons; (2) smoking history; (3) medical history, including regular care by a physician for medical conditions, whether they had heart disease or diabetes, whether they ever had an operation, and medications taken; (4) personal matters in life, eg, sexual intercourse, pregnancy; (5) menstrual history, ie, age at menarche, regularity of periods; (6) current life (related to self-esteem and self-efficacy); (7) work history outside of school or the home; and (8) thoughts about the future, ie, college, job, any plans.
Statistical analyses were done on a personal computer using SAS Statistical software procedures that included descriptive statistics and logistic regression analysis.3
Participation in any physical activity, either the special program or a high school athletic team, was dichotomized as high level or vigorous, coded 1/0. (Table 1). Carbonated beverage consumption variables were dichotomized as yes or no and coded as 1/0. Bone fractures were dichotomized as yes or no and coded as 1/0. Table 2 gives the results for all fractures. Analyses were also done in which bone fractures that happened when the girl was younger than 8 years old were excluded because it was felt fractures that early in life were not likely to be associated with carbonated beverage consumption. Table 3 gives the results when fractures that occurred before the age of 8 were coded as 0 in the analyses relating carbonated beverage consumption to bone fractures. Results based on analyses of the data on all fractures irrespective of time of occurrence did not differ significantly from the analyses that excluded those that occurred when the girl was younger than 8 years. Therefore, the results in Table 3 will not be discussed further.
The mean (SD) age of the girls was 15 years 8 months (10 months). One girl was in the 11th grade; 2, in the 12th grade; and the rest were either ninth or 10th graders. Of the total sample of 460, 55.65% did not participate in any sports activity; the rest participated in either the special physical activity program, the regular high school sports' teams, or both programs. With respect to activity level, 10.9% reported themselves as being "inactive"; 22.0% as engaging in "light" activity; 28.7%, in "moderate" activity; and 17.2%, in "high-level" activity; and 18.5%, in "vigorous" activity; 2.8% did not specify activity level participation. Nearly 80% drink carbonated beverages at present; 49.8%, cola beverages only, 11.5%, noncola beverages only; and 15.0%, both cola and noncola beverages. Thus, nearly two thirds of the 460 high school girls consumed cola drinks. Of those who consumed carbonated beverages, most drank regular (sugar) in contrast to diet drinks; only 20% of the participants drank diet drinks, either diet cola or other diet drinks. One fifth of the girls reported a history of a bone fracture at any age; 9 girls reported having had fractures when younger than 8 years old. The activity level was associated with neither the drinking of carbonated beverages nor the type of beverage they consumed, ie, cola or noncola. Similarly, participation in either the special program or the high school teams activities was not associated with drinking carbonated beverages (Table 1).
Table 2 gives the results for the association of carbonated beverage consumption and bone fractures among all girls, active girls, and less active girls, controlling for participation in physical activity programs and for the level of activity, ie, high or low. For all girls, the odds ratio (OR) for the association of bone fractures and drinking carbonated beverages is 3.14 (95% confidence limit [CL], .45, 6.78), P=.004.
Table 2, B, gives the results comparing the group who drank either no carbonated beverages or noncola beverages with the group who drank either cola drinks only or both cola and noncola drinks. For the active girls the OR=4.94 (95% CL, 1.79, 13.62), P=.002, while for less active girls, the OR=1.16 (96% CL, 0.60, 2.24), P=.66.
Table 2, C, gives the ORs for 3 comparisons of noncarbonated beverages with noncola beverages only; cola beverages only; and both cola and noncola beverages. For active girls, the ORs are, respectively, for consumers of noncola beverages only, 0.43(95% CL, 0.05, 4.22), P=.47; cola beverages only, 2.83 (95% CL, 0.87, 9.23), P=.09;and both cola and noncola beverages,=7.00 (95% CL, 2.00, 24.46), P=.002. The χ21 trend is statistically significant, (P=.001), indicating a dose-response relationship. For less active girls the results are marginally significant for cola drinkers; but, for the noncola drinkers: OR=4.27 (95% CL, 1.40, 13.07), P=.01.
In summary, from Table 2, B and C, we observed that for less active girls, the association between carbonated cola beverages and bone fractures is marginal; however, for active girls who consume both cola and noncola drinks, the risk of bone fractures was highest.
One health impact of carbonated beverage consumption among teenaged girls, the risk of bone fractures, is reported herein. Among all the girls, the OR for the association between carbonated beverages and bone fractures is 3.14 (95% CL, 1.45, 6.78), P=.004. Among physically active girls, the risk was highest for those who consumed both cola and noncola beverages, as compared with those who did not drink carbonated beverages, the OR being 7.00 (95%CL, 2.00, 24.45), P=.002. This association between cola drinks and bone fractures among physically active adolescents confirms results from previous work.2
Teens have doubled or tripled their consumption of soft drinks and they have cut their consumption of milk by more than 40%.1 Low bone mineral density is due to genetic, hormonal, or environmental factors, eg, diet may be causally related to fractures.4 Calcium and calcium supplementation have been found to increase bone mineral density.5-7 Osteoporotic fractures may be affected by diet and activity among young women.8 Adolescence could be a critical period for bone mass formation; adolescent females at the time of puberty may be the optimal population for early prevention of osteoporosis with calcium intake.9,10 Laboratory investigators have reported possible bone resorption from high levels of phosphorus intake.11,12 Others have found that there may be a deleterious effect on bone owing to the change in the calcium-phosphorus ratio in the diet.13,14 The association observed may be because of the phosphoric acid content in cola drinks.2,15 As long ago as the 19th century, an increase in bone fractures from occupational exposure to phosphorus was reported.16,17 Research to elucidate and understand the biological mechanism by which cola drinks may lead to bone fractures among physically active girls is needed.
Our present results confirm earlier findings,2 but the study has some of the following possible limitations. The design is cross-sectional and causality cannot be inferred from the data; causality could be inferred from a longitudinal study. Further, a study design with mineral density measurements would have been preferable for the assessment of the relationship between carbonated beverage consumption and fractures; such measurements were not part of the study design. The questionnaire did not include questions on calcium consumption, so the effect of calcium consumption could not be assessed. The teenaged subjects studied provided information on whether they consumed carbonated beverages and the types of these beverages, ie, cola or noncola, regular or diet, but not on the amount. No difference between regular and diet drinks was found; but no questions were asked regarding caffeinated vs noncaffeinated drinks.
The data were self-reports of adolescent girls via self-administered questionnaires. The girls were informed in their classrooms of the study's importance, and they were asked to respond as accurately and as completely as they could. On the whole, the responses were complete, internally consistent, and had face validity. The results obtained in this study confirm the relationship between cola consumption and bone fractures among physically active girls found in a smaller sample of adolescent girls.2 In the earlier study, calcium intake and the calcium-phosphorus ratio were assessed and controlled for in the analyses.2 Despite our study's limitations, the results reported herein warrant attention and confirmation in longitudinal and biomedical studies.
In conclusion, nationally, there is great concern about the effects of carbonated beverage consumption on obesity, tooth decay, osteoporosis, and other health problems.1 Concern about the health impact of carbonated beverage consumption, in particular, the association with bone fractures in adolescent girls, is validated by our findings. Our findings have implications both for the health of teenagers and for the health of women at later ages. In addition to research, health and social policies to promote better behavioral practices, including one's diet, among American women of all ages are needed.
Accepted for publication November 10, 1999.
I thank Rose Frisch, PhD, who was responsible for the administration of the project and for its development.
Reprints: Grace Wyshak, PhD, Department of Population and International Health, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115 (e-mail: email@example.com).
Wyshak G. Teenaged Girls, Carbonated Beverage Consumption, and Bone Fractures. Arch Pediatr Adolesc Med. 2000;154(6):610–613. doi:10.1001/archpedi.154.6.610
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