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ORIGINAL RESEARCH COMMUNICATION |
1 From the Human Nutrition Laboratory, Institute of Food Science and Nutrition, ETH Zurich, Zurich, Switzerland (IA and MBZ); the Clinic for Endocrinology and Diabetes, University Hospital Zurich, Zurich, Switzerland (RL, GAS, and KB); the Children's Hospital of Eastern Switzerland, St Gallen, Switzerland (Dl'A); and the Child Development Center, University Children's Hospital, Zurich, Switzerland (LM)
See corresponding editorial on page 895.
| ABSTRACT |
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Objectives: We aimed to determine whether LDL particle size is associated with dietary factors and specifically with fructose intake in normal-weight and overweight children.
Design: In a cross-sectional study of normal-weight and overweight 6–14 y-old Swiss children (n = 74), dietary intakes were assessed by using two 24-h-recalls and a 1-d dietary record. Body mass index (BMI) and waist-hip ratio (WHR) were measured, and plasma lipid profile and LDL particle size were determined.
Results: Compared with the normal-weight group, overweight children had significantly higher plasma triacylglycerol concentrations, lower HDL-cholesterol concentrations, and smaller LDL particle size (P < 0.05). LDL particle size was inversely correlated to BMI SD scores and WHR (P = 0.007). Although there were no significant differences in total fructose intake, the overweight children consumed a significantly (P < 0.05) higher percentage of fructose from sweets and sweetened drinks than did the normal-weight children. After control for adiposity, the only dietary factor that was a significant predictor of LDL particle size was total fructose intake (P = 0.024).
Conclusions: In school-age children, greater total and central adiposity are associated with smaller LDL particle size and lower HDL cholesterol. Overweight children consume more fructose from sweets and sweetened drinks than do normal-weight children, and higher fructose intake predicts smaller LDL particle size.
Key Words: Fructose children diet LDL particle size overweight
| INTRODUCTION |
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HFCS is not a commonly used sweetener in Western Europe. In Switzerland, the origin of most free dietary fructose is fruit and vegetables, and overall fructose intakes are lower than those in the United States. Little is known about the metabolic effects of low-to-moderate levels of free fructose intake. Moreover, there are few data on the potential adverse effects of fructose consumption in children.
Smaller LDL particle size is associated with the metabolic syndrome and may be an early-onset risk factor for atherosclerosis and type 2 diabetes (9-11). Although obesity and central adiposity in adults and older children are associated with smaller LDL particle size (12-15), there are few data in younger, prepubertal children. Moreover, the dietary determinants of LDL particle size in children have not been studied. Therefore, the aim of the present study was to investigate the relations between dietary intakes—specifically, fructose consumption—and obesity, distribution of body fat, plasma lipids, and LDL particle size in a cohort of Swiss schoolchildren.
| SUBJECTS AND METHODS |
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Written informed consent was obtained from the parents, and oral informed assent was obtained from the children. Ethical approval for the study was obtained from the Ethics Committee of the Swiss Federal Institute of Technology in Zürich.
Methods
For the dietary assessment, each child was interviewed twice for a 24-h record, and each child filled in one 1-d weighed food record. Each child was visited at the family home 3 times within 3 wk by the same trained interviewer. The 24-h recalls were done at the first and second visits; at the second visit, the interviewer also gave instructions and guidelines for the use of the 1-d weighed food record. At the third visit, the 1-d food record was carefully reviewed with the parent and the child, and an appointment was scheduled at the hospital clinic, at the parents convenience, usually within 1–2 wk of the dietary assessment. Volumes and portion sizes for the 24-h recalls were estimated by using measuring cups and spoons, photographs of food portions, and graduated food samples of cheese and bread. The combination of 24-h recalls and a food record provides a good overview of a child's habitual diet; this approach has been validated in children as young as 8 y old (17).
The physical activity of the children was assessed with the use of a questionnaire, which asked about the amount of time spent in organized sports, watching television, and playing computer games. On the day of the blood sampling, the children presented to the hospital clinic in the morning after a 12-h overnight fast. A blood sample (12 mL) was taken by venipuncture. Height was measured to the nearest 0.5 cm with the use of a metal measuring tape (Personcheck #44 444; Medizintechnik KaWe, Kirchner & Wilhelm, Asperg, Germany), and weight was measured to the nearest 100 g with the use of a digital balance (BF 18; Beurer, Ulm, Germany). Waist and hip circumferences were measured by using a nonstretchable measuring tape. The measurements of waist and hip circumferences and skinfold thicknesses were done by 2 experienced observers (IA and IH). After a 15-min rest, supine resting blood pressure was measured by auscultation.
Laboratory analysis
Blood samples were centrifuged for 15 min at 20 °C and at 2500 RPM (Omnifuge 2.0RS; Heraeus Sepatech GmbH, Osterode, Germany). Total, HDL, and LDL cholesterol and triacylglycerols were measured in fresh serum on a Hitachi 917 analyzer (Combination Triacylglycerol GPO-PAP and HDL+ 2nd-generation kits; Roche, Basel, Switzerland). Serum was stored at –20 °C for later analysis. Nondenaturing polyacrylamide gradient gel electrophoresis (GGE) of plasma was performed at 10–14 °C in 2–16% polyacrylamide gradient gels. Gels were subjected to electrophoresis for 24 h at 125 V in tris borate buffer (pH 8.3) as described elsewhere (18, 19). Gels were fixed and stained for lipids in a solution containing Oil Red O (Sigma Chemical, St Louis, MO) in 60% ethanol at 55 °C. Gels were placed on a light source and photographed by using Luminescent Image Analyzer (LAS-3000; Fujifilm, Tokyo, Japan) detection with transmitted white light. Using public domain software from the National Institutes of Health (IMAGE; version 1.62; National Institutes of Health, Bethesa, MD), we measured the migration distance for each absorbance peak and calculated the molecular diameter corresponding to each peak from a calibration curve generated from the migration distance of size standards of known diameter. These standards include carboxylated latex beads (Duke Scientific, Palo Alto, CA), thyroglobulin, and apoferritin (HMW Std; Pharmacia, Piscataway, NJ), which have a molecular diameter of 380, 170, and 122 Å, respectively, and lipoprotein calibrators of previously determined particle size.
Statistical analysis
The data for the 3 d of dietary assessment were carefully checked and entered into EBISPRO for WINDOWS software (version 4.0; J Erhardt, University of Hohenheim, Stuttgart, Germany) by the lead interviewer (IA). This system translates the amount of food eaten into individual nutrients. The program is based on the German Food and Nutrition Database (BLS 2.3; Federal Health Department, Berlin, Germany); for foods specific to Switzerland, it incorporates values of >700 foods from the Swiss Food Composition Database (20). Energy and nutrient data were averaged across the 3 d to obtain mean daily energy and nutrient intakes for each child.
The body mass index (BMI; in kg/m2) of the children was calculated. BMI SD scores (BMI-SDS) were calculated (BMI-SDS = individual BMI value – reference mean BMI value divided by SD to scale the data for comparison across ages and sex) and used as age- and sex-independent values in the analysis. Age- and sex-specific criteria from the Centers for Disease Control and Prevention (CDC; 21) were used to classify children as normal-weight, above the 85th percentile, or above the 95th percentile. Although the CDC uses the terms "at risk for overweight" for children between the 85th and the 95th percentiles and "overweight" for children above the 95th percentile, in the present study, we used the terms "overweight" for the former and "obese" for the latter. This wording is consistent with that in a previous study in which these criteria were validated in Swiss children at the same age (22).
Statistical analyses were performed by using SPSS for WINDOWS statistical software (version 13.0; SPSS Inc, Chicago, IL). Nonnormally distributed variables were log transformed for comparisons. One-way analysis of variance (ANOVA) with a post hoc Bonferroni test was used to compare means. Pearson correlations were used to investigate the relation between measures of adiposity and LDL particle size. To analyze the associations of dietary factors and metabolic parameters with LDL particle size, multivariate regressions were done. All equations were checked for confounding factors, such as adiposity, age, pubertal stage, and sex, and those factors were added as covariates when necessary.
| RESULTS |
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20% higher in the overweight children than in the normal-weight children, that difference was not statistically significant. In the continuous analysis, there were strong associations between LDL particle size and BMI-SDS, an index of overall adiposity (r = –0.313, P < 0.007), and WHR, a measure of central adiposity (r = –0.444; P < 0.001).
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10 times the lowest intakes. However, the sources of fructose were different in the 2 groups: overweight children consumed significantly less fructose, as a percentage of total fructose, from fruit and vegetables and significantly more fructose from sweets and sweetened drinks (P < 0.05 for both).
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| DISCUSSION |
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0.5% of daily energy intake. This is
5% of the mean intakes in US adults, who derive
9% of their daily energy from fructose (8). Although the median intake in the present study was low, the highest intake was
10 times the lowest intake; children with the highest intakes were consuming >10 g/d. In the present study, overweight children consumed a significantly higher percentage of fructose originating from sweets and sweetened drinks and a significantly lower percentage of fructose originating from fruit and vegetables than did normal-weight children. To our knowledge, these are the first published data on fructose consumption in normal-weight and overweight children in Europe. High intakes of fructose have been implicated in the development of dyslipidemia and obesity (2, 23). High intakes of dietary fructose induce hyperlipidemia in rodents (1), but studies on the effects of fructose intake on plasma lipids in adults are equivocal. Several studies have shown the effects of a high fructose intake on plasma lipids—in particular, the triacylglycerol concentrations increased (7, 24); however, other studies did not show such effects (8, 25). In our study, compared with normal-weight children, overweight children had significantly lower HDL-cholesterol concentrations and smaller LDL particle size and significantly greater plasma triacylglycerol concentrations. This finding is consistent with 2 previous studies in obese older children and adolescents (26, 27). However, there was no association between fructose consumption and HDL, LDL, or total cholesterol or triacylglycerols. We are aware of no previous studies on fructose intake and dyslipidemia in children.
The dietary determinants of LDL particle size in adults and children are uncertain. Several studies have shown that short-term high-carbohydrate diets lead to a reduction in LDL particle size (28-31), but those studies investigated the total carbohydrate intake, not the intakes of specific types of carbohydrates. The major new finding of the present study is that higher intakes of dietary fructose predict smaller LDL particle size in young children, independent of adiposity. This association was found despite overall fructose intakes that were lower than those found in countries where HFCS is widely used as an added sweetener. Although the total free fructose intake predicted smaller LDL particle size, there was no significant relation between the intake of fructose derived from fruit and vegetables (intrinsic sources) or the amount added to sweets and sweetened drinks and LDL particle size. Thus, we could not distinguish whether a particular source of dietary fructose was responsible for an observed relation with LDL particle size.
Fructose intakes were correlated with LDL particle size but not with adiposity or any other lipid variable in the children in the present study, which suggests that one of the earliest metabolic effects of higher fructose intake may be modulation of LDL particle size. This finding is consistent with a previous study in adults with coronary artery disease (32), in which changes in LDL particle size appeared to precede other dyslipidemic changes.
The present study had some limitations. Because it was cross-sectional, the directionality of the reported associations cannot be established, and the sample size may have been insufficient to detect weak associations. However, studies in young children on the determinants of LDL particle size are valuable because the findings are usually not confounded by chronic disease or smoking and alcohol consumption. Moreover, dietary assessment, which is always challenging, is particularly so in children, because their ability to record or remember their diet and their knowledge of food and food preparation are limited (33, 34). We used a rigorous method that required 3 home visits and combined 24-h recalls and weighed food records—2 complementary assessment tools (17)
The pattern B phenotype (a predominance of small, dense LDL) is a common finding in obese adults, and this phenotype is linked to a greater incidence of cardiovascular disease (11). The present study shows that LDL particle size in overweight children is smaller than that in normal-weight children. However, the mean LDL particle size of 285.68 Å observed in the overweight children still exceeds the 264 Å that is considered the lower limit of large, buoyant LDL particle size for adults. However, the smaller LDL particle size in the overweight children may represent an early, subtle shift toward the dyslipidemic pattern of small, dense LDL particles often found in obese adults.
| ACKNOWLEDGMENTS |
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The authors responsibilities were as follows—All authors: contributed to the study design; IA, MBZ, RL, GAS, and DA: performed the fieldwork and the data collection; IA, KB, MBZ, and GAS: supervised the laboratory analysis and completed the data analysis. IA, KB, and LM: conducted the statistical analysis; IA, MZ, and KB: wrote the first draft of the manuscript; and all authors: edited the manuscript. None of the authors had a personal or financial conflict of interest.
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