Food sources of nutrients among 13-year-old Portuguese adolescents

Eating out of home in Portugal: characterisation and effects on dietary intake

This cross-sectional study aims to describe and compare energy, nutrient intake and food consumption according to eating location and by age groups using data from the National Food, Nutrition and Physical Activity Survey (IAN-AF 2015/2016). Dietary intake was estimated by two non-consecutive days of food diaries (children)/24-h recalls (other age groups), and four eating location categories were defined according to the proportion of meals consumed at out-of-home locations: Home (at least 80 % of meals at home), Other Homes, School or Work and Restaurants and Other Places. The majority of meals (69·1 %) were consumed at home. Meals were also often taken at school by children and adolescents and in restaurants and similar outlets by adults and elderly. Children and adolescents in the School or Work category ate more fruit, vegetables and pulses and cereals and starchy tubers, whereas adults in this category ate more red and processed meats, sugar-sweetened beverages and sweets. Compared with Home category, Restaurants and Other Places was associated with worse diet adequacies among children (β = -1·0; 95 % CI = -2·0, -0·04), adolescents: (β = -2·4; 95 % CI = -3·2, -1·5) and adults (β = -1·3; 95 % CI = -1·6, -1·0) reflecting higher intakes of energy, fat, trans-fatty acids and SFA, and Na. The elderly consumed more free sugars and fat when eating out of home in general. Overall, findings reflect important variation in nutrient profiles by eating location, with meals taken at school or work contributing to higher consumption of nutrient-dense foods and those taken in restaurants and other similar settings implying higher consumption of energy-dense foods.

Prevalence of nutritional inadequacy in children aged 12-36 months: EPACI Portugal 2012

Adequate nutritional intake in the first years of life is crucial for future health. The purpose of this study is to assess the adequacy of nutritional intake in Portuguese toddlers. The EPACI Portugal 2012 is a cross-sectional study of a representative sample of toddlers (n = 2230), aged between 12 and 36 months. Data on diets were collected by trained interviewers. The current analysis included 853 children with full data from 3-day food diaries completed by parents/caregivers. Intakes of energy, macro- and micronutrients were estimated through Statistical Program to Assess Dietary Exposure (SPADE). Nutritional adequacy was evaluated using Dietary Reference Values established by the European Food Safety Authority. A large proportion of children exceeded the recommended energy intake. The median daily protein intake was 4.7 g/kg/day, five times more than that recommended. About 9% and 90% of the children consumed a lower proportion of energy than the lower limit of the Reference Intake range for carbohydrates and fat, respectively. Around a third consumed less fibre and magnesium and 100% less vitamin D than the recommended Adequate Intake (AI). Almost a third consumed less vitamin A than the recommended Average Requirement (AR) and 86% of the children showed excessive sodium consumption. Portuguese toddlers consumed a low proportion of energy from fat, had energy and protein intakes above the recommendations and excessive intakes of sodium, and inadequate intakes of vitamin A. Every child consumed less than the recommended AI for vitamin D.

A lower energy intake contributes to a better cardiometabolic profile in adolescence: Data from the EPITeen cohort

Caloric restriction has been associated with improved cardiometabolic health. Available data in humans are commonly based on short follow-up periods, specific diets, or population groups. We hypothesized that participants of a population-based cohort (Epidemiological Health Investigation of Teenagers in Porto) with a dietary pattern characterized by a lower energy intake during adolescence have a better cardiometabolic profile in adolescence and young adulthood than other dietary patterns. At aged 13 and 21 year evaluations, diet, anthropometric, and cardiometabolic measures were assessed. Diet was assessed through a food frequency questionnaire and, at 13 years, summarized in dietary patterns identified by cluster analysis. The lower intake dietary pattern included 40% of the participants. The energy intake misreport was estimated using the Goldberg method. Analysis of variance and analysis of covariance were used to compare cardiometabolic risk factors according to dietary patterns. The mean energy intake was 2394 and 2242 Kcal/d for the total sample at aged 13 years (n = 962) and 21 years (n = 862), respectively. Those belonging to the lower intake dietary pattern showed a 25% and 5% lower energy intake, respectively. In the cross-sectional analysis at aged 13, adolescents belonging to the lower intake dietary pattern presented lower glucose, insulin, triglycerides, and blood pressure values after adjusting for body mass index and parents' education level. Among the plausible reporters, differences were only statistically significant for glucose and systolic blood pressure. Our data support that a dietary pattern characterized by a lower energy intake may contribute to a better cardiometabolic profile in adolescents. However, no significant effect was found in young adulthood.

Relative Validity of a Semi-Quantitative Food Frequency Questionnaire for Adolescents

<b><i>Introduction:</i></b> A valid food frequency questionnaire (FFQ) is a priority for epidemiological studies. We aimed to perform a relative validity of an FFQ for Portuguese adolescents. <b><i>Methods:</i></b> A semi-quantitative Portuguese FFQ (SQ-PortFood-FQ) was developed and the relative validity performed using the multiple-pass 24-h recall. Eighty adolescents (aged 10–17 years) completed both questionnaires to measure energy intake, macro- and specific micronutrient intake. We used the following methods for the relative validity: (1) Spearman’s correlation coefficient (<i>r</i>); (2) cross-classification into the same third (agreement) and into the opposite third (disagreement); (3) weighted κ-coefficient (κ_W); (4) and the Bland-Altman method. <b><i>Results:</i></b> We obtained acceptable correlation coefficients between questionnaires for energy (<i>r =</i>0.59;<i> p</i> &#x3c; 0.001), protein (<i>r =</i>0.60;<i> p</i>&#x3c; 0.001), fat (<i>r</i> = 0.55;<i> p</i> &#x3c; 0.001), carbohydrates (<i>r =</i>0.51;<i> p</i> &#x3c; 0.001) and sodium (<i>r =</i>0.51;<i> p</i> &#x3c; 0.001). Tertile agreement for energy, protein, fat, carbohydrates and vitamin C intakes classified correctly more than 50% and grossly misclassified less than 10% of participants. Energy and protein produced moderate agreement between methods with a κ_W &#x3e;0.40. The SQ-PortFood-FQ overestimated all analysed data when compared to the 24-h recall, although those estimations were &#x3c;10% for energy, macronutrients and cholesterol. The 95% limits of agreement showed that all the variables (energy, protein, fat, carbohydrates, fibre, calcium, sodium, iron, saturated fatty acids, monounsaturated fatty acids and cholesterol) were within the desirable limits of agreement of 50–200%, with the exception of vitamin C (76–296%) and polyunsaturated fatty acids (PUFA) (75–232%). <b><i>Discussion/Conclusion:</i></b> The SQ-PortFood-FQ showed acceptable relative validity at the individual level for energy, protein, fat, carbohydrates, fibre, calcium, sodium, iron, saturated fatty acids, monounsaturated fatty acids and cholesterol. Non-significant relationships were found for vitamin C and PUFA. Our results are in line with previous studies carried out amongst adolescents. As far as we know this is the first FFQ validated for Portuguese adolescents.

Evaluating the association of free sugars intake and glycemic load on cardiometabolic outcomes: A prospective analysis throughout adolescence into early adulthood

PURPOSE

To prospectively evaluate the relation of free sugars intake and glycemic load with adiposity and insulin resistance, from adolescence into early adulthood.

METHODS

Data from the population-based cohort EPITeen (Porto, Portugal) at 13 and 21 years old was used (n = 1034). At both ages, dietary assessment was obtained by food frequency questionnaires (FFQ). Added sugar of each food item was estimated based on a systematic methodology described by Louie et al. Free sugars (FS) were defined according to World Health Organization. To each food item of the FFQ, a calculated mean value of FS and glycemic index was assigned. Dietary glycemic load (GL) was determined for each participant. Sex- and age-specific body mass index z-score (BMIz) and waist-to-weight ratio (WWr) were used as measures of adiposity, and the homeostasis model assessment (HOMA-IR) as a measure of insulin resistance. A cross-lagged path analysis was performed to examine causal relationships between FS intake or dietary GL with BMIz, WWr or HOMA-IR.

RESULTS

No significant association was found between intake of FS and dietary GL at 13 years with BMIz, WWr or HOMA-IR at 21. A significant inverse association was found between BMIz at 13 and FS (β = -0.595,95%CI -0.830, -0.359) and dietary GL (β = -0.687,95%CI -0.937,-0.437) at 21 years. Intake of FS, dietary GL, as well as BMIz, WWr and HOMA-IR tracked from 13 to 21 years.

CONCLUSION

No significant association was found between consumption of FS and GL at 13 years with cardiometabolic features at 21 years. Dietary intake and cardiometabolic outcomes tracked from adolescence into early adulthood.

Adherence to Southern European Atlantic Diet and physical fitness on the atherogenic index of plasma in adolescents

We sought (i) to evaluate the associations of cardiorespiratory fitness (CRF), muscular fitness (MF) and Southern European Atlantic Diet (SEADiet) with atherogenic index of plasma (AIP) and (ii) to investigate de combined association of MF, CRF and SEADiet on AIP in adolescents. A cross-sectional school-based study was conducted on 493 adolescents (285 girls and 208 boys) aged 15-18 years, from the Portuguese Azorean Archipelago. CRF was measured by shuttle run test and MF by curl up and push up tests. Adherence to SEADiet was assessed with a semi-quantitative food frequency questionnaire (FFQ). The AIP was estimated as log (TG/HDL-C). Measures of pubertal stage and socioeconomic status were assessed. Linear regression showed a significant inverse association between MF (standardized β = -0.165; p < 0.001), CRF (standardized β = -0.081; p < 0.030) and SEADiet (standardized β = -0.081; p < 0.045) with AIP, after adjustments for age, sex, pubertal stage and parental education. Furthermore, participants classified with an optimal as well as those with low adherence to a SEADiet but with LowMF/LowCRF had on average the highest AIP (F(7.482) = 3.270; p = 0.002). Moreover, optimal SEADiet with HighMF/HighCRF group showed the lowest AIP when compared with those with low adherence to a SEADiet with HighMF/HighCRF group (p = 0.03). AIP is inversely associated with MF, CRF and SEADiet. The low MF combined with a low CRF levels seems to overcome the potential healthy effect of having an optimal adherence to the SEADiet on AIP. However, an optimal adherence to SEADiet seems to improve the AIP in those adolescents with high fitness levels.

The Relationship between Lifestyle Factors and Obesity Indices among Adolescents in Qatar

Background: Physical inactivity, sedentary behaviour and an unhealthy diet are factors that may increase weight and general and/or abdominal obesity. Objective: To evaluate the relationship between general and abdominal obesity and lifestyle factors among adolescents in Qatar. Methods: The study data are based on the Arab Teens Lifestyle Study (ATLS). The target population consisted of 1184 adolescents aged between 14 and 18 years old (563 boys and 621 girls), randomly selected through multistage sampling. A validated questionnaire was used to collect data on lifestyle indicators. Anthropometric indicators, which included body weight, height and waist circumference (WC), were measured according to standardised procedures. International Obesity Task Force (IOTF) age- and sex-specific body mass index (BMI) reference values were used to define overweight and obesity. Abdominal obesity was defined by the 'waist-to-height ratio' (WHtR > 0.5) and by sex- and age-specific WC cutoff values. Results: Females were more inactive than males (63.7% vs. 36.3%; p < 0.001). The proportion of adolescents who reported screen time of over 2 h per day was 82.5%. Females engaged in more sedentary behaviour than males (53.4% vs. 46.4%, p = 0.009). Being male (OR: 1.3; CI: 1.0-1.7) and skipping breakfast (OR: 1.5; CI: 1.2-2) were significantly associated with overweight/obesity. In contrast, high intake of fast food, fries, sweets and cake were negative predictors of general and abdominal obesity. Conclusions: The findings revealed the prevalence of unhealthy lifestyle habits among adolescents in Qatar and indicated relationships between certain dietary habits and obesity. The findings of this study may help in advocating for the implementation of an intervention that includes lifestyle changes targeting adolescents.

Food intake and high-sensitivity C-reactive protein levels in adolescents

BACKGROUND AND AIMS

Diet comprises factors with anti and pro-inflammatory potential that can contribute to modulate obesity-induced inflammation. We aimed to assess the association between food intake and high-sensitivity C-reactive protein (hsCRP) levels in adolescents.

METHODS AND RESULTS

A cross-sectional analysis of 991 adolescents aged 13 years old was conducted as part of the EPITeen cohort, Porto, Portugal. Food intake was assessed by a food frequency questionnaire and thirteen food groups were defined. Anthropometric assessment was performed and serum hsCRP was measured in a fasting blood sample. hsCRP concentrations above the 75th percentile were considered high. Logistic regression was fitted to estimate the association between the intake frequency of the food groups and hsCRP, stratified by BMI and adjusted for sex, parental education and total energy intake. Median (25-75th percentiles) hsCRP concentrations increased with increasing values of BMI [normal weight: 0.20 (0.10-0.50); overweight: 0.40 (0.20-0.80); obese: 1.10 (0.40-2.15) mg/l, p < 0.001]. After adjustment for sex, parental education and total energy intake, no statistically significant associations were found amongst normal weight and overweight participants. However, among obese individuals, having as reference the first frequency category (<1 per day), a higher frequency of vegetables/legumes intake showed a decreased odds of high hsCRP levels (OR: 0.10, 95%CI 0.03-0.38, 1-3 per day; and OR: 0.14, 95%CI 0.04-0.52, >3 per day).

CONCLUSION

Among participants with obesity-induced higher hsCRP levels, a higher frequency of vegetable/legume intake was inversely related to hsCRP.

Foods Contributing to Macronutrient Intake of Women Living in Puerto Rico Reflect Both Traditional Puerto Rican and Western-Type Diets

Lack of variability in dietary intake within a population makes identification of relationships between diet and disease difficult. Studies in populations with greater interindividual variation can provide important insights. The Puerto Rican diet is in transition from a traditional to a more Western-type diet, resulting in greater interindividual variability. We identified foods contributing to absolute intake and variability in the intake of macronutrients among Puerto Rican women. One hundred women, aged 30⁻79, residents of San Juan, Puerto Rico, completed three, interviewer-administered, 24-h dietary recalls from which foods contributing to absolute intake and intake variability in intake of energy, fat, protein, carbohydrate and dietary fiber were determined. The overall prevalence of intake of foods was also calculated. Traditional Puerto Rican foods such as legumes, rice, and plantains were important contributors to the intake of calories and macronutrients as were foods more typical of Western diets including white bread and sweetened carbonated beverages. Identification of food sources of nutrients for this population with a diet in transition can contribute to the development of instruments to measure dietary intake and to understand the contribution of diet to the etiology of chronic disease among Puerto Rican women.

Relationship between dietary vitamin D and serum 25-hydroxyvitamin D levels in Portuguese adolescents

OBJECTIVE

To understand the relationship between vitamin D intake and serum 25-hydroxyvitamin D (25(OH)D) levels in a sample of Portuguese adolescents.

DESIGN

Cross-sectional evaluation carried out in the 2003/2004 school year. Vitamin D intake was assessed by an FFQ and 25(OH)D was measured in a fasting blood sample.

SETTING

Public and private schools in Porto, Portugal.

SUBJECTS

Adolescents aged 13 years (n 521) enrolled at school (EPITeen cohort).

RESULTS

Both mean (sd) intake and serum 25(OH)D level were far below the recommended, 4·47 (2·49) µg/d and 16·5 (5·7) ng/ml, respectively. A significant difference in serum level was found according to season, with lower values in winter than summer (14·8 (4·6) v. 17·3 (5·9) ng/ml, P<0·001). Vitamin D intake was weakly correlated with serum 25(OH)D (r=0·056, P=0·203).

CONCLUSIONS

Dietary vitamin D and serum 25(OH)D levels were positively but weakly correlated and the error was higher among those with higher serum 25(OH)D concentration. Our results support the need for strategies that promote increase of the most important food sources of vitamin D to reduce the high prevalence of low vitamin D status.

Vitamin D levels and cardiometabolic risk factors in Portuguese adolescents

BACKGROUND

Growing evidence suggests a possible association between low vitamin D levels and increased cardiovascular risk. However, research regarding the period of adolescence is scarce. We aimed to evaluate the association of vitamin D, intake and serum 25(OH)D levels, with cardiometabolic risk factors in 13-year-old adolescents.

METHODS

We conducted a cross-sectional analysis of 1033 adolescents evaluated at 13years old as part of the population-based cohort EPITeen. Vitamin D intake was assessed by a food frequency questionnaire. Serum 25(OH)D levels were assessed for a subsample of 514 participants. Metabolic syndrome (MetS) features were defined according to the National Cholesterol Education Program Adult Treatment Panel III definition modified for age. Logistic regression was fitted to estimate the association between vitamin D status and cardiometabolic risk factors, adjusting for sex, parental education, BMI, physical activity and season.

RESULTS

Mean (SD) vitamin D levels, 4.61 (2.50)μg for intake and 16.52 (5.72)ng/mL for serum, were below the recommendations. The prevalence of MetS was 13.2%. Total cholesterol and LDL levels significantly decreased with 25(OH)D serum increase. After adjustment, no association was found between vitamin D levels and MetS. Regarding MetS features, an increased odds of high BMI was observed for those with a lower intake (OR 1.87 95% CI 1.04-3.35).

CONCLUSIONS

Although a significant increase in total and LDL cholesterol was observed for lower 25(OH)D levels, and an increased odds of high BMI was observed for those with a lower vitamin D intake, no significant association was observed between vitamin D levels and metabolic syndrome.

Eating out of home and dietary adequacy in preschool children

The present study aims to describe dietary intake and dietary adequacy according to eating location in preschool children. A sub-sample of 2414 children from the Generation XXI birth cohort (Porto, Portugal), evaluated during the follow-up between 2009 and 2011, was included. Dietary intake was assessed by 3 d food diaries and four groups of children were defined according to the eating location: 'Home' ( ≥ 80% of meals at home), 'Other homes', 'Preschool' and 'Restaurants'. A dietary adequacy index was developed based on general recommendations for children; a higher score represents a better dietary adequacy. The comparison of nutrients and foods daily intake according to the eating location groups was performed by ANOVA and ANCOVA to adjust for potential confounders. Children classified in 'Preschool' group ate significantly more vegetables, fruit, bread and fish, and less meat, compared to children classified into the 'Home' group. Children classified in the 'Restaurants' group ate more cakes, salty snacks and fruit juices than children in 'Home' group; and less vegetables, dairy products and pasta/rice/potatoes. In 'Restaurants' children obtained the lowest mean score of the dietary adequacy index (15.5, 95% CI 14.8, 16.3) and in 'Preschool' children had the highest mean score (18.3, 95% CI 18.1, 18.4), corresponding to a better dietary adequacy. Preschools seem to have a relevant role in promoting the intake of healthy foods in preschool children. The consumption in restaurants/coffee shops seems to contribute to energy-dense food intake and reduced consumption of nutrient-dense foods.

Food consumption, physical activity and socio-economic status related to BMI, waist circumference and waist-to-height ratio in adolescents

OBJECTIVE

To examine the association between obesity and food group intakes, physical activity and socio-economic status in adolescents.

DESIGN

A cross-sectional study was carried out in 2008. Cole's cut-off points were used to categorize BMI. Abdominal obesity was defined by a waist circumference at or above the 90th percentile, as well as a waist-to-height ratio at or above 0·500. Diet was evaluated using an FFQ, and the food group consumption was categorized using sex-specific tertiles of each food group amount. Physical activity was assessed via a self-report questionnaire. Socio-economic status was assessed referring to parental education and employment status. Data were analysed separately for girls and boys and the associations among food consumption, physical activity, socio-economic status and BMI, waist circumference and waist-to-height ratio were evaluated using logistic regression analysis, adjusting the results for potential confounders.

SETTING

Public schools in the Azorean Archipelago, Portugal.

SUBJECTS

Adolescents (n 1209) aged 15-18 years.

RESULTS

After adjustment, in boys, higher intake of ready-to-eat cereals was a negative predictor while vegetables were a positive predictor of overweight/obesity and abdominal obesity. Active boys had lower odds of abdominal obesity compared with inactive boys. Boys whose mother showed a low education level had higher odds of abdominal obesity compared with boys whose mother presented a high education level. Concerning girls, higher intake of sweets and pastries was a negative predictor of overweight/obesity and abdominal obesity. Girls in tertile 2 of milk intake had lower odds of abdominal obesity than those in tertile 1. Girls whose father had no relationship with employment displayed higher odds of abdominal obesity compared with girls whose father had high employment status.

CONCLUSIONS

We have found that different measures of obesity have distinct associations with food group intakes, physical activity and socio-economic status.

Dietary patterns among 13-y-old Portuguese adolescents

OBJECTIVE

The aim of this study was to identify dietary patterns in 13-y-old adolescents and to evaluate their association with socioeconomic and behavioral factors.

METHODS

Data from 1489 adolescents born in 1990 and enrolled in schools of Porto, Portugal, in 2003-2004 (EPITeen study) were analyzed, after excluding those without information on the food frequency questionnaire and the outliers. The questionnaire items were grouped into 14 food groups and dietary patterns were identified by cluster analysis (k-means). Their association with participants' characteristics was computed using multinomial logistic regression.

RESULTS

Four dietary patterns were identified. The pattern healthier (16.1%) was characterized by the highest consumption of seafood, soup, vegetables/legumes, fruit, and added fats. The dairy products pattern (29.7%) showed the highest consumption of dairies. The pattern fast food and sweets (14.2%) presented the highest intake of fast food, sweets and pastry, soft drinks and coffee or tea. The lower intake pattern (40%) was characterized by a lower consumption of the majority of food groups. A higher odds of belonging to the fast food and sweets pattern, compared with the lower intake pattern was found among adolescents spending more time watching TV on the weekends (>360 min: odds ratio [OR], 2.09; 95% confidence interval [CI], 1.23-3.57) and among those consuming four to seven fried meals per week (OR, 3.96; 95% CI, 2.27-6.90). Adolescents with highly educated parents were less likely to belong to the fast food and sweets group.

CONCLUSION

Unhealthier behaviors and lower socioeconomic position were the main factors associated with the unhealthier dietary pattern (fast food and sweets). This information should be considered in the development of health-promotion interventions.

Associations between a posteriori defined dietary patterns and bone mineral density in adolescents

PURPOSE

Dietary pattern analysis may uncover the joint effects of multiple dietary components on bone health, but such research is scarce and targets mostly adults.

METHODS

We quantified prospective associations between dietary patterns and bone mineral density (BMD) in 1,007 adolescents of a cohort born in 1990 and recruited at schools in Porto during the 2003/2004 school year. Forearm BMD was measured using dual-energy X-ray absorptiometry. Participants' dietary patterns were classified "Healthier", "Dairy products", "Fast food and sweets" and "Lower intake" according to previously identified patterns obtained in a larger sample of 1,489 participants using the K-means method. Using dietary patterns at 13 years old as the main exposure, associations were estimated cross-sectionally (with BMD at the age of 13) and prospectively (with annual BMD variation between 13 and 17 years), using linear regression coefficients adjusted for height, weight, energy intake and, in girls, for menarche age.

RESULTS

No significant associations between the a posteriori dietary patterns identified and mean BMD at 13 were found. However, among girls, adherence to a pattern characterized by low intake of energy and all food groups was negatively associated with annual BMD variation between 13 and 17 years [adjusted coefficient (95 % CI) -0.451 (-0.827; -0.074) mg·cm⁻²·year⁻¹].

CONCLUSIONS

Although results showed that, in girls, adherence to a "Lower intake" dietary pattern is associated with lower annual BMD variation throughout adolescence, overall, there were no consistent associations between dietary patterns and forearm BMD in adolescents.

Associations between a priori-defined dietary patterns and longitudinal changes in bone mineral density in adolescents

OBJECTIVE

To quantify short- and long-term associations between dietary patterns defined a priori and bone mineral density (BMD) during adolescence.

DESIGN

Dietary patterns were defined at 13 years old using a Mediterranean diet (MD) quality index, the Dietary Approaches to Stop Hypertension (DASH) diet index and the Oslo Health Study (OHS) dietary index. Linear regression coefficients were used to estimate associations between dietary patterns and forearm BMD at 13 and 17 years, measured by dual-energy X-ray absorptiometry.

SETTING

Public and private schools of Porto, Portugal.

SUBJECTS

The EPITeen cohort comprising 1180 adolescents born in 1990, recruited at schools during the 2003/2004 school year and re-evaluated in 2007/2008.

RESULTS

In girls, at 13 years, mean BMD (g/cm2) in the first and third tertiles was 0·369 and 0·368 for the MD pattern, 0·368 and 0·369 for the DASH diet, and 0·370 and 0·363 for the OHS index. In boys, mean BMD (g/cm2) in the first and third tertiles was 0·338 and 0·347 for the MD pattern, 0·342 and 0·346 for the DASH diet, and 0·344 and 0·342 for the OHS index. None of these differences were significant. Mean BMD at 17 years and prospective variation were also not significantly different between tertiles of adherence to each score. However, a trend of increased BMD at 13 years with greater adherence to the MD pattern was observed in boys (adjusted coefficient = 0·248; 95% CI 0·052, 0·444).

CONCLUSIONS

The selected dietary patterns may not capture truly important dietary differences in determining BMD or diet may not be, beyond nutrient adequacy, a limiting determinant of BMD.

Caffeine intake reduces sleep duration in adolescents

In our study, we hypothesized that higher caffeine intake would be associated with lower sleep duration among 13-year-old adolescents. In addition, we aimed to identify food sources of caffeine intake in this sample. Eligible participants were adolescents who were born in 1990 and attended school in Porto, Portugal, in 2003/2004. Self-administered questionnaires were used, and diet was evaluated using a food frequency questionnaire. From the 2160 eligible participants, only 1522 with valid information regarding their diet were included in this study. In our sample, the median intake of caffeine was 23.1 mg/d, with soft drinks being the major source. Ice tea presented the highest median (25th-75th percentiles) contribution (33.1% [14.0-52.1]), followed by cola (21.1% [6.4-37.6]). Regarding cocoa products, chocolate bars presented a median contribution of 5.1% (1.0-14.0), and snacks containing chocolate had a contribution of 3.0% (0.5-7.2). Coffee and tea presented a negligible contribution. Adolescents who reported less sleep duration and those who spent more time watching TV during the weekend had a significantly higher caffeine intake. Overall, boys had higher intakes of caffeine from soft drinks, and private school attendees, those who had parents with more education, who reported less television viewing time and had lower body mass index presented higher intakes of caffeine from chocolate. Considering sleeping more than 9.5 hours as a reference class, for each increase of 10 mg/d in caffeine intake, we found that the odds ratio of sleeping 8.5 hours or less was 1.12 (95% confidence interval, 1.06-1.19). Our results support the hypothesis that caffeine intake was inversely associated with sleep duration in adolescents.

Sleep duration and adiposity during adolescence

BACKGROUND AND OBJECTIVE

The association between sleep and obesity has been described in different age groups. However, there are not sufficient data to clarify the inconsistent results reported in adolescents. Our objective was to study the associations between sleep duration and adiposity at 13 and at 17 years of age, with both cross-sectional and longitudinal approaches.

METHODS

We evaluated, as part of an urban population-based cohort (EPITeen), 1171 adolescents at both 13 and 17 years of age. Sleep duration was estimated by self-reported bedtimes and wake-up times. Age- and gender-specific BMI z scores were calculated based on Centers for Disease Control and Prevention references. Body fat percentage (BF%) was assessed by bioelectrical impedance. Regression coefficients (β) and respective 95% confidence intervals (CIs) were used to estimate the association between sleep and BMI z scores and BF%. Additionally, a cross-lagged analysis was performed to investigate the causal relations.

RESULTS

In the cross-sectional analysis, at 13 years, sleep duration was inversely associated with BMI z score only in boys (β = -0.155, 95% CI: -0.267 to -0.043); at 17 years, a positive association was found among girls but was only significant for BF% (β = 0.510, 95% CI: 0.061-0.958). In the longitudinal approach, sleep duration at age 13 was inversely associated with BMI z score (β = -0.123, 95% CI: -0.233 to -0.012) and BF% (β = -0.731, 95% CI: -1.380 to -0.081) at 17 years only in boys. These significant associations disappeared after adjustment for adiposity at 13 years. These results were corroborated by those from cross-lagged analysis.

CONCLUSIONS

Our results showed an effect of sleep duration in adiposity at younger ages of adolescence and suggested gender differences in this association.