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Dietary behavior is among the important modifiable patient-associated factors for optimizing health among youth with diabetes. It is also well established that youth with either type 1 diabetes (T1DM) or with type 2 diabetes (T2DM) have increased risk for cardiovascular complications later in life.1 The joint American Heart Association (AHA)/American Diabetes Association (ADA) Scientific Statement emphasizes the importance of weight management, medical nutrition therapy and physical activity in prevention of cardiovascular disease in people with diabetes.2 The statement also explicitly indicates that all of the recommendations for patients with T2DM appear appropriate for individuals with T1DM as well.
Medical nutrition therapy principles and recommendations for people with diabetes released by the ADA stress the importance of sufficient intake of certain foods and nutrients, such as whole grains, fruits, vegetables, and low-fat milk and lower consumption of others, including saturated fats.3 However, a large proportion of youth with diabetes do not follow the nutrition recommendations.4 Unhealthy diet may contribute to increased risk of other cardiovascular risk factors or complications in these patients.5 Detailed exploration of factors associated with unhealthy diet in youth with diabetes is needed.
The objective of this study is to explore demographic, socio-economic, diabetes-related and behavioral correlates of dietary intake of dairy, fruits, vegetables, sweetened soda, fiber, calcium, and saturated fat in youth with T1DM and T2DM using data from the SEARCH for Diabetes in Youth Study.
The SEARCH study is an ongoing multi-center study based on ascertainment of cases of physician-diagnosed diabetes mellitus in youth younger than age 20 years beginning in 2001 and continuing through the present. SEARCH has six centers, located in Ohio, Colorado, Washington, South Carolina, Hawaii, and California. Diabetes cases were also identified among three American Indian populations in Arizona and Colorado and among members of the Gila River Pima Indian community participating in the National Institute of Diabetes and Digestive and Kidney Diseases Pima Indian Diabetes Study. A detailed description of the SEARCH study was published elsewhere.6 The study was reviewed and approved by the local Institutional Review Boards at each center. Parents of participants under age 18 years at the time of data collection provided informed consent and minor participants assented; all participants aged 18 years or older provided signed informed consent.
The SEARCH food frequency questionnaire (FFQ) has been described in detail previously.4 The FFQ consisted of 85 food lines for which the participant indicated if the item(s) was/were consumed in the past week (“yes/no”) and if yes, how many days, and the average portion size. The food groups were created by either collapsing food lines based on their major components, or by disaggregating composite foods into constituent foods. The FFQ was self-administered by study participants age 10 years or older after careful instruction by study staff. A small percentage (7%) of FFQs were interviewer-administered because of participant difficulties in form completion.
The nutrient and portion-size databases for this instrument were modified from the respective Diabetes Prevention Program databases, using the Nutrition Data System for Research (database 3 version 4.05/33, 2002, Nutrition Coordinating Center, University of Minnesota, Minneapolis) and industry sources. This analysis focused on dairy, fruits, vegetables, sweetened soda, total fiber, calcium, and percent of calories from saturated fat. This selection was based on the components’ likely influence on metabolic status and on the development of complications associated with diabetes.
Race and ethnicity were obtained through self-report using the standard census questions.7 Highest parental education was based on the parent with the highest education as reported on a questionnaire. Household income was assessed through self-report in predetermined categories. Type of diabetes was based on the clinical diagnosis by the physician. Diabetes treatment mode, diabetes duration, diabetes-related self-care, weight management and parental education on healthy food choices were included in the analysis as probable correlates of dietary adherence. Diabetes-related self-care was assessed by the question “How much of your own diabetes care do you do for yourself?” with answers categorized as “none”, “less than 25%”, “25–75%”, “more than 75%” and “all”. Diabetes education was assessed by the question to the parent “Have you been taught about how to make healthy food choices?” Weight management and physical activity were assessed by questions developed for the Youth Risk Behavior Surveillance System (YRBSS).8 Weight management goal was assessed with a question “Which of the following are you trying to do about your weight?” with possible answers “not trying to do anything”, “trying to lose”, “trying to gain”, and “trying to stay the same weight”. Physical activity was assessed by the question: “On how many of the past 7 days did you exercise or participate in a physical activity for at least 20 minutes that made you sweat and breathe hard?” Sedentary behavior was assessed by a slightly modified YRBSS question “On each weekday, about how much do you usually spend watching TV?”
This analysis included youth whose diabetes was prevalent in 2001 or incident in 2002–2005 who participated in the SEARCH examination. Of the 11,437 registered, valid subjects, 8,338 youth (73%) were contacted by phone and had an initial patient survey; of these, 5,293 youth (63%) attended the SEARCH clinic visit; 3,074 of whom were age-eligible (10 years and older at the study visit) and completed the dietary assessment. Among these youth, we excluded those with provider-defined diabetes type other than type 1 and type 2 or with type missing (n=27); diabetes duration less than 6 months (n=369); race/ethnicity other than non-Hispanic white, African American, Hispanic, Asian/Pacific Islander, or Native American (n=12); and those who reported eating much more or much less in the week when food intake was assessed than their typical week (n=154). A total of 533 observations were excluded from the analysis due to one or more criteria listed above; data from 2,541 youth were included in these analyses.
Analyses were conducted using the SAS (version 9.1, 2003, SAS Institute Inc, Cary, NC). Across subgroups of demographic, socio-economic, behavioral and diabetes-related variables, the medians of intake were compared by means of quantile regression.9 We also explored the overall significance of the association for covariates with more than 2 levels or categories (i.e. race/ethnicity, income, diabetes-related self-management and weight management) with Wald test. Due to the number of statistical tests conducted, alpha=.01 was used to determine statistical significance.
Of the 2,541 youth, 2,176 had T1DM and 365 had T2DM (Table 1). As compared to youth with T1DM, those with T2DM were older, more likely to be females, and more likely to be from a minority racial/ethnic group (Asian Pacific Islanders, African Americans, Hispanic, and Native Americans). Median intake for selected food groups and nutrients, as well as lower and upper quartiles, is presented by diabetes type (Table 2). All estimates of dietary intake presented in Tables 2 to to44 are per 1000 kcal of total energy intake.
Among youth with T1DM, older participants had lower dairy and calcium intake and higher soda intake in comparison to younger youth (Table 3). Males had lower consumption of vegetables, fruits, and fiber, and higher consumption of soda and saturated fat than females. In comparison to non-Hispanic whites, African Americans had lower dairy and calcium intake and higher soda intake (Table 3).
Among the youth with T2DM, participants age 15 years and older had higher soda intake than the younger ones. The median consumption of dairy and calories from saturated fat by Native Americans was lower than intake by non-Hispanic whites. On the other hand, vegetable, total fiber and soda intake was higher in Native Americans than in whites. Hispanics also consumed more fiber than non-Hispanic whites. Calcium intake was highest in Hispanics and lowest in Asian/Pacific Islanders (p=0.03).
As shown in Table 4, after adjustment for age, gender and race/ethnicity, among youth with T1DM, lower parental education was significantly associated with lower fruit intake. Youth from low income families consumed less calcium than youth from high income families. Among youth with T2DM, family income was associated with sweetened soda and vegetable intake. Soda consumption was higher in youth from medium-income families (household income $25,000–$74,999) as compared to high-income families ($75,000 and greater), whereas vegetable consumption was highest in high-income families and lowest in medium-income families.
Diabetes-related self-management, weight control efforts and parent education about healthy food choices were significant correlates for food and nutrient intake in youth with T1DM after adjustment for age, gender and race/ethnicity (Table 4). Youth with less self-management had higher fruit intake and lower saturated fat intake. Lower vegetable intake was associated with parental education about healthy food choices. Those youth who were trying to gain weight had lower vegetable intake as contrasted to those who tried to lose weight (p<0.01).
Among youth with T1DM, watching television for ≥ 2 hours every weekday was associated with lower fruit and total fiber intake (Table 4). On the other hand, fruit intake was higher among youth who were involved in rigorous physical activity 3 days per week or more as compared to those who had less rigorous physical activity. In the T2DM group, rigorous physical activity was associated with higher calcium intake (Table 4)
The ADA recommends inclusion of whole grains, fruits, vegetables, and low-fat milk in a healthy diet and discourages excessive intake of saturated fats.3 We have previously shown that a significant proportion of youth with diabetes does not meet AHA/ADA recommendations.4 In this study we explored the correlates of selected food and nutrient intake among these youth.
Gender differences in diet found in youth with T1DM include higher intake of vegetables, fruits, and total fiber by females, and higher intake of soda and percent of calories from saturated fat by males. In this study, females had a healthier diet at least with respect to the foods and nutrients included in this analysis, which may be associated with the higher prevalence of dieting among female than male adolescents. Forty percent of females with T1DM reported that they were trying to lose weight as compared with 21% of males. Among youth with T2DM, 82% of females and 73% of males reported that they were trying to lose weight. Higher prevalence of healthful dieting among females with T1DM than in males with T1DM may explain the observed differences in dietary intake between males and females. Increased prevalence of overweight among T1DM and T2DM found in the recent study may contribute to the dieting behavior in these youth. 10
Among racial/ethnic groups, non-Hispanic white youth seem to eat the healthiest diet, regardless of diabetes type. They consumed more dairy, calcium and less sweetened soda than African American youth. Higher calcium and dairy intake in whites as compared to other race/ethnicity groups was reported by Xie et al.11 Consistent with the results of these analyses, Storey et al12 and Xie et al11 both found that family income had a positive association with calcium and dairy consumption among adolescents. Moreover, we observed an association of income with soda intake in T2DM youth, which is similar with the data presented by Xie et al11 for added sugar.
Watching television more than 2 hours per day was associated with a poorer diet – less fruits and fiber. Using YRBSS data, Pate et al13 reported that, among high school students, watching television was associated with low levels of physical activity. Furthermore, low activity was associated with eating less fruits and vegetables. Wilson et al14 found that both low exercise frequency and decreased consumption of vegetables and milk/dairy products by high school students was associated with smoking. Lowry et al15 found that trying to lose weight was associated with increased fruit and vegetable consumption in adolescent males. To summarize, diet, physical activity, and other lifestyle and behavioral factors represent complex set of interconnected variables affecting the health of youth with diabetes.
Besides the strengths of the SEARCH study which include among others large sample size and diverse populations, our study has some limitations. The cross-sectional study design, though adequate for exploratory association studies, does not allow any causal inferences. Lack of precision in diet measurement may have had an impact on the results of the study. Food frequency questionnaire usually tends to underestimate the actual intake.16 Moreover, random error in diet estimates may result in insufficient power to detect small differences between groups. We also found that participation in the SEARCH baseline study visit declined with increasing age. Non-participants to the in-person research visits may differ in terms of diet structure from those who actively collaborate with study personnel. Specifically, the latter may have a healthier diet in comparison to those who refused to participate in the study. Groups with low socio-economic status may be underrepresented in our sample. All these probably affect absolute estimates of intake, but are unlikely to substantially influence the associations found in the analysis.
This study has several potential clinical and research implications. Recent nutritional management guidelines for youth with diabetes provide comprehensive recommendations on dietary treatment.17 Data provided by our study may help dietitians to focus on groups of youth with diabetes who have lower adherence to a healthy diet. Youth with diabetes who adhere poorly to dietary guidelines are more likely to be minority male adolescents aged fifteen and above with low level of parental education and low or middle family income; low parental involvement in diabetes management; and a sedentary lifestyle; all of which are additional risk factors for inadequate diet. Therefore, diet counseling groups may be tailored according to these major determinants of diet behavior among youth with diabetes.
SEARCH for Diabetes in Youth is funded by the CDC (PA number 00097 and DP-05-069) and supported by the NIDDK. Site Contract Numbers: Kaiser Permanente Southern California (U01 DP000246), University of Colorado Health Sciences Center (U01 DP000247), Pacific Health Research Institute (U01 DP000245), Children’s Hospital Medical Center (Cincinnati) (U01 DP000248), University of North Carolina (U01 DP000254), University of Washington School of Medicine (U01 DP000244), Wake Forest University School of Medicine (U01 DP000250).
The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention and the National Institute of Diabetes and Digestive and Kidney Diseases.
The SEARCH for Diabetes in Youth Study is indebted to the many youth and their families, and their health care providers, whose participation made this study possible.
The authors acknowledge the involvement of General Clinical Research Centers (GCRC) at the following institutions in the SEARCH for Diabetes in Youth Study: Medical University of South Carolina (Grant Number M01 RR01070); Cincinnati Children’s Hospital (Grant Number M01 RR08084); Children’s Hospital and Regional Medical Center and the University of Washington School of Medicine (Grant Number M01RR00037 and M01RR001271); Colorado Pediatric General Clinical Research Center (Grant Number M01 RR00069).
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