Statistical methods to assess and minimize the role of intra-individual variability in obscuring the relationship between dietary lipids and serum cholesterol

A validation study comparing energy and nutrient intake between a web-based food frequency questionnaire and a 4-d dietary record

OBJECTIVE

Reliable assessments of dietary intake is crucial when examining associations between dietary factors and different outcomes. Today, web-based instead of paper-based food frequency questionnaires (FFQs) are common. A web-based FFQ implies a different experience (including design differences, the possibility only to show relevant questions, and automatic checks for completeness) and may capture dietary intake differently. The aim of this study was to validate a well-used paper-based FFQ transferred to a web-based version against a 4-d dietary record.

METHODS

Baseline data from a dietary intervention study comprising women and men with type 2 diabetes were used. Diet was assessed with the web-based FFQ and a 4-d dietary record. Energy intake and energy-adjusted nutrient intakes were assessed and compared using Spearman's rank correlation and Bland-Altman analysis. The analysis included 101 participants.

RESULTS

The average energy intake with the FFQ was 2068 kcal, 157 kcal higher than the average from the dietary record. Significant deattenuated correlations were found for intake of energy (r = 0.37; 95% confidence interval [CI],0.19-0.53), carbohydrates (r = 0.85; 95% CI, 0.78-0.89), protein (r = 0.53; 95% CI, 0.38-0.66) and fat (r = 0.59; 95% CI, 0.44-0.70). Significant deattenuated correlations (ranging r = 0.26-0.73) were found for intake of alcohol, whole grain, fiber, saturated fat, monounsaturated fat, polyunsaturated fat, cholesterol, vitamins A, B12, C, D, and E, folate, iron, potassium, magnesium, and calcium. Bland-Altman analyses showed no clear trends but wide limits of agreement.

CONCLUSION

Overall, the web-based FFQ performed well and is similar to the paper-based version. It can be a useful tool for dietary assessments.

Effects of sleep quality on diurnal variation of brain volume in older adults: A retrospective cross-sectional study

AIM

Brain volume is influenced by several factors that can change throughout the day. In addition, most of these factors are influenced by sleep quality. This study investigated diurnal variation in brain volume and its relation to overnight sleep quality.

METHODS

We enrolled 1,003 healthy Koreans without any psychiatric disorders aged 60 years or older. We assessed sleep quality and average wake time using the Pittsburgh Sleep Quality Index, and divided sleep quality into good, moderate, and poor groups. We estimated the whole and regional brain volumes from three-dimensional T1-weighted brain MRI scans. We divided the interval between average wake-up time and MRI acquisition time (INT) into tertile groups: short (INT1), medium (INT2), and long (INT3).

RESULTS

Whole and regional brain volumes showed no significance with respect to INT. However, the `interaction between INT and sleep quality showed significance for whole brain, cerebral gray matter, and cerebrospinal fluid volumes (p < .05). The INT2 group showed significantly lower volumes of whole brain, whole gray matter, cerebral gray matter, cortical gray matter, subcortical gray matter, and cerebrospinal fluid than the INT1 and INT3 groups only in the individuals with good sleep quality.

CONCLUSION

Human brain volume changes significantly within a day associated with overnight sleep in the individuals with good sleep quality.

Dietary fat quality, plasma atherogenic lipoproteins, and atherosclerotic cardiovascular disease: An overview of the rationale for dietary recommendations for fat intake

The scientific evidence supporting the current dietary recommendations for fat quality keeps accumulating; however, a paradoxical distrust has taken root among many researchers, clinicians, and in parts of the general public. One explanation for this distrust may relate to an incomplete overview of the totality of the evidence for the link between fat quality as a dietary exposure, and health outcomes such as atherosclerotic cardiovascular disease (ASCVD). Therefore, the main aim of the present narrative review was to provide a comprehensive overview of the rationale for dietary recommendations for fat intake, limiting our discussion to ASCVD as outcome. Herein, we provide a core framework - a causal model - that can help us understand the evidence that has accumulated to date, and that can help us understand new evidence that may become available in the future. The causal model for fat quality and ASCVD is comprised of three key research questions (RQs), each of which determine which scientific methods are most appropriate to use, and thereby which lines of evidence that should feed into the causal model. First, we discuss the link between low-density lipoprotein (LDL) particles and ASCVD (RQ1); we draw especially on evidence from genetic studies, randomized controlled trials (RCTs), epidemiology, and mechanistic studies. Second, we explain the link between dietary fat quality and LDL particles (RQ2); we draw especially on metabolic ward studies, controlled trials (randomized and non-randomized), and mechanistic studies. Third, we explain the link between dietary fat quality, LDL particles, and ASCVD (RQ3); we draw especially on RCTs in animals and humans, epidemiology, population-based changes, and experiments of nature. Additionally, the distrust over dietary recommendations for fat quality may partly relate to an unclear understanding of the scientific method, especially as applied in nutrition research, including the process of developing dietary guidelines. We therefore also aimed to clarify this process. We discuss how we assess causality in nutrition research, and how we progress from scientific evidence to providing dietary recommendations.

Validation of an interviewer-administered seven-day semi-quantitative food frequency questionnaire for the dietary assessment of preschool children in rural Bangladesh

A validation study of an interviewer-administered, seven-day semi-quantitative food frequency questionnaire (7-d SQFFQ) was conducted in Bangladeshi rural preschool age children. Using a cross-sectional study design, 105 children from 103 households were randomly selected. For the SQFFQ, a list of commonly consumed foods was adapted from the Bangladesh national micronutrient survey 2011–12. The data on the actual number of times and the amount of the children's consumption of the foods in the preceding 1 week were collected by interviewing the mothers. The intake was compared with two non-consecutive days 24-h dietary recalls conducted within 2 weeks after the SQFFQ. Validity was assessed by the standard statistical tests. After adjusting for the energy intake and de-attenuation for within-subject variation, the food groups (cereals, animal source foods, milk and the processed foods) had ‘good’ correlations between the methods (rho 0⋅65–0⋅93; P < 0⋅001). Similarly, the macronutrients (carbohydrate, protein and fats) had ‘good’ correlations (rho 0⋅50–0⋅75; P < 0⋅001) and the key micronutrients (iron, zinc, calcium, vitamin A, etc.) demonstrated ‘good’ correlations (rho 0⋅46–0⋅85; P < 0⋅001). The variation in classifying the two extreme quintiles by the SQFFQ and the 24-h recalls was <10 %. The results from Lin's concordance coefficients showed a ‘moderate’ to ‘excellent’ absolute agreement between the two methods for food groups, and nutrients (0⋅21–0⋅90; P < 0⋅001). This interviewer-administered, 7-d SQFFQ with an open-ended intake frequency demonstrated adequate validity to assess the dietary intake for most nutrients and suitable for dietary assessments of young children in Bangladesh.

Relative Validity of an Italian EPIC Food Frequency Questionnaire for Dietary Factors in Children and Adolescents. A Rizzoli Orthopedic Institute Study

Dietary factors play a major role in the development of non-communicable diseases, however little is known regarding the impact of nutrition on rare diseases like sarcomas. This Rizzoli Orthopedic Institute study aimed to evaluate the relative validity of a Food Frequency Questionnaire (FFQ) to measure the consumption of foods in comparison with a 3-days diary diet in a healthy Italian student population aged between 12 and 17 years. An extended version (including food groups for children) of the semi-quantitative FFQ used in the European Prospective Investigation into Cancer and Nutrition (EPIC) was administered. The validity of the FFQ was assessed by comparing the intakes from the FFQ against the 3-day diary method. 254 Italian subjects were included in the analyses: 128 females; 126 males; 116 from High Secondary School (14-17 years); 138 from Low Secondary School (12-13 years). Mean and median intakes are overall higher in the FFQs than in the food diaries. Spearman correlations adjusted for within-person variability were highest for legumes, vegetables and coffee/tea (>0.5), followed by potatoes, meat, fruits, breakfast cereals, biscuits and candies, and milk/yoghurts (>0.4). Moderate correlations were found for alcoholic drinks, soft drinks, juices, and grains (>0.3). For some food groups, such as fish, potatoes, and bread, correlations tend to become higher when stratifying the analyses for age group. These results demonstrate that the adapted EPIC COS FFQ validated in Italian adults is also appropriate and well understood by Italian children and adolescents.

Within-Person Variation in Nutrient Intakes across Populations and Settings: Implications for the Use of External Estimates in Modeling Usual Nutrient Intake Distributions

Determining the proportion of a population at risk of inadequate or excessive nutrient intake is a crucial step in planning and managing nutrition intervention programs. Multiple days of 24-h dietary intake data per subject allow for adjustment of modeled usual nutrient intake distributions for the proportion of total variance in intake attributable to within-individual variation (WIV:total). When only single-day dietary data are available, an external adjustment factor can be used; however, WIV:total may vary by population, and use of incorrect WIV:total ratios may influence the accuracy of prevalence estimates and subsequent program impacts. WIV:total values were compiled from publications and from reanalyses of existing datasets to describe variation in WIV:total across populations and settings. The potential impact of variation in external WIV:total on estimates of prevalence of inadequacy was assessed through simulation analyses using the National Cancer Institute 1-d method. WIV:total values were extracted from 40 publications from 24 countries, and additional values were calculated from 15 datasets from 12 nations. Wide variation in WIV:total (from 0.02 to 1.00) was observed in publications and reanalyses. Few patterns by population characteristics were apparent, but WIV:total varied by age in children (< vs. >1 y) and between rural and urban settings. Simulation analyses indicated that estimates of the prevalence of inadequate intake are sensitive to the selected ratio in some cases. Selection of an external WIV:total estimate should consider comparability between the reference and primary studies with regard to population characteristics, study design, and statistical methods. Given wide variation in observed ratios with few discernible patterns, the collection of ≥2 days of intake data in at least a representative subsample in population dietary studies is strongly encouraged. In the case of single-day dietary studies, sensitivity analyses are recommended to determine the robustness of prevalence estimates to changes in the variance ratio.

Within- and Between-Household Variation in Food Expenditures Among Low-Income Households Using a Novel Simple Annotated Receipt Method

Background: Household food purchasing behavior has gained interest as an intervention to improve nutrition and nutrition-associated outcomes. However, evaluating food expenditures is challenging in epidemiological studies. Assessment methods that are both valid and feasible for use among diverse, low-income populations are needed. We therefore developed a novel simple annotated receipt method to assess household food purchasing. First, we describe and evaluate the extent to which the method captures food purchasing information. We then evaluate within- and between-household variation in weekly food purchasing to determine sample sizes and the number of weeks of data needed to measure household food purchasing with adequate precision.

Methods: Four weeks of food purchase receipt data were collected from 260 low-income households in the Minneapolis-St. Paul metropolitan area. The proportion of receipt line items that could not be coded into one of 11 food categories (unidentified) was calculated, and a zero-inflated negative binomial regression was used to evaluate the association between unidentified receipt items and participant characteristics and store type. Within- and between-household coefficients of variation were calculated for total food expenditures and several food categories.

Results: A low proportion of receipt line items (1.6%) could not be coded into a food category and the incidence of unidentified items did not appreciably vary by participant characteristics. Weekly expenditures on foods high in added sugar had higher within- and between-household coefficients of variation than weekly fruit and vegetable expenditures. To estimate mean weekly food expenditures within 20% of the group's usual (“true”) expenditures, 72 households were required. Nine weeks of data were required to achieve an r = 0.90 between observed and usual weekly food expenditures.

Conclusions: The simple annotated receipt method may be a feasible tool for use in assessing food expenditures of low-income, diverse populations. Within- and between-household coefficients of variation suggest that the number of weeks of data or group sizes required to precisely estimate usual household expenditures is higher for foods high in added sugar compared to fruits and vegetables.

Within-person, between-person and seasonal variance in nutrient intakes among 4- to 8-year-old rural Zambian children

Estimates of the components of nutrient intake variation are needed for modelling distributions of usual intake or predicting the usual intake of individuals. Season is a potential source of variation in nutrient intakes in addition to within- and between-person variation, particularly in low- or middle-income countries. We aimed to describe seasonal variation in nutrient intakes and estimate within-person, between-person and other major components of intake variance among Zambian children. Children from rural villages and peri-urban towns in Mkushi District, Zambia aged 4-8 years were enrolled in the non-intervened arm of a randomised controlled trial of pro-vitamin A carotenoid biofortified maize (n 200). Up to seven 24-h dietary recalls per child were obtained at monthly intervals over a 6-month period covering the late post-harvest (August-October), early lean (November-January) and late lean (February-April) seasons (2012-2013). Nutrient intakes varied significantly by season. For energy and most nutrients, intakes were highest in the early lean season and lower in the late post-harvest and late lean seasons. Season and recall on a market day had the strongest effects on nutrient intakes among covariates examined. Unadjusted within- to between-person variance ratios ranged from 4·5 to 31·3. In components of variance models, season accounted for 3-20 % of nutrient intake variance. Particularly in rural settings in low- and middle-income countries, where availability of locally grown, nutrient-rich foods may vary seasonally, studies should include replicates across seasons to more precisely estimate long-term usual intakes.

No one accelerometer-based physical activity data collection protocol can fit all research questions

Background

Measuring physical activity and sedentary behavior accurately remains a challenge. When describing the uncertainty of mean values or when making group comparisons, minimising Standard Error of the Mean (SEM) is important. The sample size and the number of repeated observations within each subject influence the size of the SEM. In this study we have investigated how different combinations of sample sizes and repeated observations influence the magnitude of the SEM.

Methods

A convenience sample were asked to wear an accelerometer for 28 consecutive days. Based on the within and between subject variances the SEM for the different combinations of sample sizes and number of monitored days was calculated.

Results

Fifty subjects (67% women, mean ± SD age 41 ± 19 years) were included. The analyses showed, independent of which intensity level of physical activity or how measurement protocol was designed, that the largest reductions in SEM was seen as the sample size were increased. The same magnitude in reductions to SEM was not seen for increasing the number of repeated measurement days within each subject.

Conclusion

The most effective way of reducing the SEM is to have a large sample size rather than a long observation period within each individual. Even though the importance of reducing the SEM to increase the power of detecting differences between groups is well-known it is seldom considered when developing appropriate protocols for accelerometer based research. Therefore the results presented herein serves to highlight this fact and have the potential to stimulate debate and challenge current best practice recommendations of accelerometer based physical activity research.

Corruption of the Pearson correlation coefficient by measurement error and its estimation, bias, and correction under different error models

Correlation coefficients are abundantly used in the life sciences. Their use can be limited to simple exploratory analysis or to construct association networks for visualization but they are also basic ingredients for sophisticated multivariate data analysis methods. It is therefore important to have reliable estimates for correlation coefficients. In modern life sciences, comprehensive measurement techniques are used to measure metabolites, proteins, gene-expressions and other types of data. All these measurement techniques have errors. Whereas in the old days, with simple measurements, the errors were also simple, that is not the case anymore. Errors are heterogeneous, non-constant and not independent. This hampers the quality of the estimated correlation coefficients seriously. We will discuss the different types of errors as present in modern comprehensive life science data and show with theory, simulations and real-life data how these affect the correlation coefficients. We will briefly discuss ways to improve the estimation of such coefficients.

Assessment and validation of spot urine in estimating the 24-h urinary sodium, potassium, and sodium/potassium ratio in Chinese adults

The commonly used methods of estimating the 24-h urinary sodium (UNa) and urinary potassium (UK) from spot urine (SU) are the Kawasaki method (K-method), INTERSALT method (I-method), and Tanaka method (T-method), but the method that is suitable for use in the general Chinese population is still uncertain. We aimed to assess and validate these methods in estimating the 24-h UNa and UK using SU samples in Chinese adults. We studied 1428 individuals aged 18–69 years using SU and 24-h urine samples. For the K-method, I-method, and T-method, the Pearson correlation coefficients of the 24-h UNa were 0.35, 0.35, and 0.33 (all p < 0.01), and the intraclass correlation coefficients (ICC) were 0.34, 0.26, and 0.26 (all p < 0.01), respectively. The estimated 24-h UK using the K-method and T-method had correlation coefficients of 0.36 and 0.39 (all p < 0.01) and ICCs of 0.31 and 0.27 (all p < 0.01). The mean bias for the K-method in estimating the 24-h UNa and UK were the least biased among these methods. The bias between the 24-h urine Na/K ratio and the spot urinary Na/K ratio by the Bland–Altman method was −0.22. These methods for estimating the 24-h UNa and UK from SU were inadequate at the population level in Zhejiang Province, although the K-method showed the least bias among these methods. The spot urine Na/K ratio may be a useful and alternative method for 24-h urine collection for the estimation of the urinary Na/K ratio in the Chinese population.

Reliability of Repeated Measures of Nutrient Intake by Diet Records in Residents in the Western Region of Japan

OBJECTIVE

We aimed to assess the day-to-day variation in twelve one-day diet records over one year from 131 residents of urban and rural areas in the western region of Japan.

METHODS

Between 2014 and 2015, the participants provided repeated one-day diet records once a month. We estimated the intraclass correlation coefficient (ICCs) for intakes for energy and 39 crude and energy-adjusted nutrients using linear mixed models.

RESULTS

Among the unadjusted nutrients, ICCs ranged from 0.05 (95 percent confidence interval = 0.03-0.09) for vitamin A retinol equivalent (RE) to 0.55 (95% CI = 0.48-0.62) for potassium. After energy adjustment, the ICCs were 0.02 (95 percent confidence interval = 0.03-0.09) for vitamin A (RE) and 0.52 (95 percent confidence interval = 0.45-0.59) for potassium. Intakes of energy-adjusted macronutrients tended to have moderate degrees of day-to-day coefficients of variation (CV_w, range = 0.13-0.23, mean = 0.18), while the coefficients of variation for intakes of micronutrients varied dramatically (CV_w, range = 0.17-2.59, mean = 0.54).

CONCLUSION

There were large day-to-day variations in nutrient intake assessed by diet records among urban and rural residents in the western region of Japan. This study provided information on the reproducibility of crude and energy-adjusted nutrients that may be useful for other dietary studies in Japanese populations.

Validation of a semi-quantitative FFQ for 18-month-old toddlers: the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study

OBJECTIVE

Dietary intake of toddlers has been of growing interest due to its long-term consequences on health. However, previous works have focused largely on Caucasian populations and less is known about Asian toddlers. We aimed to validate a semi-quantitative FFQ designed to assess dietary intakes of 18-month-old toddlers in a multi-ethnic Asian cohort.

DESIGN

An FFQ of ninety-four food items, identified based on food records of 12-month-old GUSTO children, the Southampton Women's Survey 12 Month Infancy Questionnaire and inputs from paediatric dietitians, was filled out two weeks before the 18th-month clinic visit. As the reference method, two non-consecutive 24 h recalls (24HR) were administered during and two weeks after the clinic visit. FFQ nutrient intakes were validated against averaged 24HR nutrient intakes, using the Wilcoxon signed-rank test, Spearman's rank-order correlation, cross-classification and the Bland-Altman method.

SETTING

Data from the Singapore Growing Up in Singapore Towards Healthy Outcomes (GUSTO) mother-offspring birth cohort.ParticipantsToddlers (n 188) aged 18 months.

RESULTS

Absolute nutrient intakes from the FFQ were significantly higher than from the 24HR, except for vitamin A. After energy adjustments, r range was 0·56-0·78 (macronutrients) and 0·40-0·54 (micronutrients). De-attenuation increased r to 0·58-0·96 and 0·45-0·65 for macro- and micronutrients, respectively. Of participants, ≥82·4 % (macronutrients) and ≥77·7 % (micronutrients) were classified in the same and adjacent quartiles. No clear systematic increase in intake differences with increasing mean intake was observed in Bland-Altman plots.

CONCLUSIONS

This FFQ can provide a satisfactory assessment of toddlers' energy-adjusted nutrient intakes, as well as accurately rank them in a group.

Comparison of personal air benzene and urine t,t-muconic acid as a benzene exposure surrogate during turnaround maintenance in petrochemical plants

Previous studies have shown that biomarkers of chemicals with long half-lives may be better surrogates of exposure for epidemiological analyses, leading to less attenuation of the exposure-disease association, than personal air samples. However, chemicals with short half-lives have shown inconsistent results. In the present study, we compared pairs of personal air benzene and its short-half-life urinary metabolite trans,trans-muconic acid (t,t-MA), and predicted attenuation bias of theoretical exposure-disease association. Total 669 pairs of personal air benzene and urine t,t-MA samples were taken from 474 male workers during turnaround maintenance operations held in seven petrochemical plants. Maintenance jobs were classified into 13 groups. Variance components were calculated for personal air benzene and urine t,t-MA separately to estimate the attenuation of the theoretical exposure-disease association. Personal air benzene and urine t,t-MA showed similar attenuation of the theoretical exposure-disease association. Analyses for repeated measurements showed similar results, while in analyses for values above the limits of detection (LODs), urine t,t-MA showed less attenuation of the theoretical exposure-disease association than personal air benzene. Our findings suggest that there may be no significant difference in attenuation bias when personal air benzene or urine t,t-MA is used as a surrogate for benzene exposure.

Contribution to the understanding of how principal component analysis-derived dietary patterns emerge from habitual data on food consumption

Background

Principal component analysis (PCA) is a widely used exploratory method in epidemiology to derive dietary patterns from habitual diet. Such dietary patterns seem to originate from intakes on multiple days and eating occasions. Therefore, analyzing food intake of study populations with different levels of food consumption can provide additional insights as to how habitual dietary patterns are formed.

Objective

We analyzed the food intake data of German adults in terms of the relations among food groups from three 24-h dietary recalls (24hDRs) on the habitual, single-day, and main-meal levels, and investigated the contribution of each level to the formation of PCA-derived habitual dietary patterns.

Design

Three 24hDRs were collected in 2010-2012 from 816 adults for an European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam subcohort study. We identified PCA-derived habitual dietary patterns and compared cross-sectional food consumption data in terms of correlation (Spearman), consistency (intraclass correlation coefficient), and frequency of consumption across all days and main meals. Contribution to the formation of the dietary patterns was obtained through Spearman correlation of the dietary pattern scores.

Results

Among the meals, breakfast appeared to be the most consistent eating occasion within individuals. Dinner showed the strongest correlations with "Prudent" (Spearman correlation = 0.60), "Western" (Spearman correlation = 0.59), and "Traditional" (Spearman correlation = 0.60) dietary patterns identified on the habitual level, and lunch showed the strongest correlations with the "Cereals and legumes" (Spearman correlation = 0.60) habitual dietary pattern.

Conclusions

Higher meal consistency was related to lower contributions to the formation of PCA-derived habitual dietary patterns. Absolute amounts of food consumption did not strongly conform to the habitual dietary patterns by meals, suggesting that these patterns are formed by complex combinations of variable food consumption across meals. Dinner showed the highest contribution to the formation of habitual dietary patterns. This study provided information about how PCA-derived dietary patterns are formed and how they could be influenced.

The number of repeated observations needed to estimate the habitual physical activity of an individual to a given level of precision

Physical activity behavior varies naturally from day to day, from week to week and even across seasons. In order to assess the habitual level of physical activity of a person, the person must be monitored for long enough so that the level can be identified, taking into account this natural within-person variation. An important question, and one whose answer has implications for study- and survey design, epidemiological research and population surveillance, is, for how long does an individual need to be monitored before such a habitual level or pattern can be identified to a desired level of precision? The aim of this study was to estimate the number of repeated observations needed to identify the habitual physical activity behaviour of an individual to a given degree of precision. A convenience sample of 50 Swedish adults wore accelerometers during four consecutive weeks. The number of days needed to come within 5–50% of an individual's usual physical activity 95% of the time was calculated. To get an idea of the uncertainty of the estimates all statistical estimates were bootstrapped 2000 times. The mean number of days of measurement needed for the observation to, with 95% confidence, be within 20% of the habitual physical activity of an individual is highest for vigorous physical activity, for which 182 days are needed. For sedentary behaviour the equivalent number of days is 2.4. To capture 80% of the sample to within ±20% of their habitual level of physical activity, 3.4 days is needed if sedentary behavior is the outcome of interest, and 34.8 days for MVPA. The present study shows that for analyses requiring accurate data at the individual level a longer measurement collection period than the traditional 7-day protocol should be used. In addition, the amount of MVPA was negatively associated with the number of days required to identify the habitual physical activity level indicating that the least active are also those whose habitual physical activity level is the most difficult to identify. These results could have important implications for researchers whose aim is to analyse data on an individual level. Before recommendations regarding an appropriate monitoring protocol are updated, the present study should be replicated in different populations.

Improving Metabolic Health Through Precision Dietetics in Mice

The incidence of diet-induced metabolic disease has soared over the last half-century, despite national efforts to improve health through universal dietary recommendations. Studies comparing dietary patterns of populations with health outcomes have historically provided the basis for healthy diet recommendations. However, evidence that population-level diet responses are reliable indicators of responses across individuals is lacking. This study investigated how genetic differences influence health responses to several popular diets in mice, which are similar to humans in genetic composition and the propensity to develop metabolic disease, but enable precise genetic and environmental control. We designed four human-comparable mouse diets that are representative of those eaten by historical human populations. Across four genetically distinct inbred mouse strains, we compared the American diet's impact on metabolic health to three alternative diets (Mediterranean, Japanese, and Maasai/ketogenic). Furthermore, we investigated metabolomic and epigenetic alterations associated with diet response. Health effects of the diets were highly dependent on genetic background, demonstrating that individualized diet strategies improve health outcomes in mice. If similar genetic-dependent diet responses exist in humans, then a personalized, or "precision dietetics," approach to dietary recommendations may yield better health outcomes than the traditional one-size-fits-all approach.

Validation and Assessment of Three Methods to Estimate 24-h Urinary Sodium Excretion from Spot Urine Samples in High-Risk Elder Patients of Stroke from the Rural Areas of Shaanxi Province

Background: 24-h urine collection is regarded as the "gold standard" for monitoring sodium intake at the population level, but ensuring high quality urine samples is difficult to achieve. The Kawasaki, International Study of Sodium, Potassium, and Blood Pressure (INTERSALT) and Tanaka methods have been used to estimate 24-h urinary sodium excretion from spot urine samples in some countries, but few studies have been performed to compare and validate these methods in the Chinese population. Objective: To compare and validate the Kawasaki, INTERSALT and Tanaka formulas in predicting 24-h urinary sodium excretion using spot urine samples in 365 high-risk elder patients of strokefrom the rural areas of Shaanxi province. Methods: Data were collected from a sub-sample of theSalt Substitute and Stroke Study. 365 high-risk elder patients of stroke from the rural areas of Shaanxi province participated and their spot and 24-h urine specimens were collected. The concentrations of sodium, potassium and creatinine in spot and 24-h urine samples wereanalysed. Estimated 24-h sodium excretion was predicted from spot urine concentration using the Kawasaki, INTERSALT, and Tanaka formulas. Pearson correlation coefficients and agreement by Bland-Altman method were computed for estimated and measured 24-h urinary sodium excretion. Results: The average 24-h urinary sodium excretion was 162.0 mmol/day, which representing a salt intake of 9.5 g/day. Three predictive equations had low correlation with the measured 24-h sodium excretion (r = 0.38, p < 0.01; ICC = 0.38, p < 0.01 for the Kawasaki; r = 0.35, p < 0.01; ICC = 0.31, p < 0.01 for the INTERSALT; r = 0.37, p < 0.01; ICC = 0.34, p < 0.01 for the Tanaka). Significant biases between estimated and measured 24-h sodium excretion were observed (all p < 0.01 for three methods). Among the three methods, the Kawasaki method was the least biased compared with the other two methods (mean bias: 31.90, 95% Cl: 23.84, 39.97). Overestimation occurred when the Kawasaki and Tanaka methods were used while the INTERSALT method underestimated 24-h sodium excretion. Conclusion: The Kawasaki, INTERSALT and Tanaka methods for estimation of 24-h urinary sodium excretion from spot urine specimens were inadequate for the assessment of sodium intake at the population level in high-risk elder patients of stroke from the rural areas of Shaanxi province, although the Kawasaki method was the least biased compared with the other two methods.

Association of diet quality with dietary inflammatory potential in youth

Background: Diet plays a crucial role in the regulation of chronic inflammation. The sparse evidence available in adult populations indicates that diet quality is linked to the dietary inflammatory potential; however, this association has not been established in youth. Design: Data were obtained from a representative national sample of 2889 children and young people in Spain, aged 6-24 years. The dietary inflammatory potential was measured by the dietary inflammatory index (DII), and diet quality by three conceptually different measures: the Mediterranean Diet Quality Index for children and adolescents (KIDMED), energy density, and total dietary antioxidants capacity. Results: The mean DII was 1.96 ± 0.76 units Scoring for the KIDMED index and the total dietary antioxidant capacity significantly decreased (p < 0.001 and p = 0.030, respectively) across quintiles of the DII, whereas the opposite was true for energy density (p < 0.001). The effect size of these associations was strongest for energy density, followed by the KIDMED index and total dietary antioxidant capacity. Conclusion: A healthy diet characterized by high adherence to the Mediterranean diet, high total dietary antioxidant capacity, or low energy density was linked to greater anti-inflammatory potential of the diet, as measured by the DII.

Cumulative Effect of Obesogenic Behaviours on Adiposity in Spanish Children and Adolescents

OBJECTIVE

Little is known about the cumulative effect of obesogenic behaviours on childhood obesity risk. We determined the cumulative effect on BMI z-score, waist-to-height ratio (WHtR), overweight and abdominal obesity of four lifestyle behaviours that have been linked to obesity.

METHODS

In this cross-sectional analysis, data were obtained from the EnKid sudy, a representative sample of Spanish youth. The study included 1,614 boys and girls aged 5-18 years. Weight, height and waist circumference were measured. Physical activity (PA), screen time, breakfast consumption and meal frequency were self-reported on structured questionnaires. Obesogenic behaviours were defined as <1 h PA/day, ≥2 h/day screen time, skipping breakfast and <3 meals/day. BMI z-score was computed using age- and sex-specific reference values from the World Health Organization (WHO). Overweight including obesity was defined as a BMI > 1 SD from the mean of the WHO reference population. Abdominal obesity was defined as a WHtR ≥ 0.5.

RESULTS

High screen time was the most prominent obesogenic behaviour (49.7%), followed by low physical activity (22.4%), low meal frequency (14.4%), and skipping breakfast (12.5%). Although 33% of participants were free of all 4 obesogenic behaviours, 1, 2, and 3 or 4 behaviours were reported by 44.5%, 19.3%, and 5.0%, respectively. BMI z-score and WHtR were positively associated (p < 0.001) with increasing numbers of concurrent obesogenic behaviours. The odds of presenting with obesogenic behaviours were significantly higher in children who were overweight (OR 2.68; 95% CI 1.50; 4.80) or had abdominal obesity (OR 2.12; 95% CI 1.28; 3.52); they reported more than 2 obesogenic behaviours. High maternal and parental education was inversely associated (p = 0.004 and p < 0.001, respectively) with increasing presence of obesogenic behaviours. Surrogate markers of adiposity increased with numbers of concurrent presence of obesogenic behaviours. The opposite was true for high maternal and paternal education.

Comparison of a web-based food record tool and a food-frequency questionnaire and objective validation using the doubly labelled water technique in a Swedish middle-aged population

Two web-based dietary assessment tools have been developed for use in large-scale studies: the Riksmaten method (4-d food record) and MiniMeal-Q (food-frequency method). The aim of the present study was to examine the ability of these methods to capture energy intake against objectively measured total energy expenditure (TEE) with the doubly labelled water technique (TEEDLW), and to compare reported energy and macronutrient intake. This study was conducted within the pilot study of the Swedish CArdioPulmonary bioImage Study (SCAPIS), which included 1111 randomly selected men and women aged 50-64 years from the Gothenburg general population. Of these, 200 were enrolled in the SCAPIS diet substudy. TEEDLW was measured in a subsample (n 40). Compared with TEEDLW, both methods underestimated energy intake: -2·5 (sd  2·9) MJ with the Riksmaten method; -2·3 (sd 3·6) MJ with MiniMeal-Q. Mean reporting accuracy was 80 and 82 %, respectively. The correlation between reported energy intake and TEEDLW was r 0·4 for the Riksmaten method (P < 0·05) and r 0·28 (non-significant) for MiniMeal-Q. Women reported similar average intake of energy and macronutrients in both methods whereas men reported higher intakes with the Riksmaten method. Energy-adjusted correlations ranged from 0·14 (polyunsaturated fat) to 0·77 (alcohol). Bland-Altman plots showed acceptable agreement for energy and energy-adjusted protein and carbohydrate intake, whereas the agreement for fat intake was poorer. According to energy intake data, both methods displayed similar precision on energy intake reporting. However, MiniMeal-Q was less successful in ranking individuals than the Riksmaten method. The development of methods to achieve limited under-reporting is a major challenge for future research.

Rapid Assessment of Dietary Intake of Fat, Fiber, and Saturated Fat: Validity of an Instrument Suitable for Community Intervention Research and Nutritional Surveillance

Traditional methods to assess changes in dietary intake, for example food frequency questionnaires or 24-hour dietary recalls, are often not practical: they are lengthy, expensive, and unsuitable for telephone administration. This article describes the development and evaluation of an approach to the rapid assessment of the dietary intake of nutrients of most interest in health promotion research; total fat, saturated fat, dietary fiber, and percent of calories from fat. In this validation study on 97 women, short dietary questionnaires were compared to two criterion measures of usual dietary intake, a food frequency questionnaire and the mean of two four-day diet records. Correlations between self-administered short questionnaires and four-day diet records were 0.52, 0.53, 0.61, and 0.40 for total fat, percent of calories from fat, saturated fat, and dietary fiber, respectively. These correlations are similar to those observed between food frequency questionnaires and four-day diet records, which suggests that this approach to developing and administering short dietary questionnaires may be useful in situations where more expensive and time-consuming methods of dietary assessment are not practical.

IHD from copper deficiency: a unified theory

The theory, in brief outline here, implicating deficiency of Cu in the aetiology and pathophysiology of IHD explains more attributes of the disease than any other theory. This theory satisfies several of Hill's criteria of a half-century ago for deducing association between an environmental feature and presence of an illness. Most important is the temporal association between the rise of IHD and the decrease in dietary Cu since the 1930s along with a parallel increase in the supplementation of pregnant women with Fe, a Cu antagonist. There are more than eighty anatomical, chemical and physiological similarities between animals deficient in Cu and individuals with IHD. Few of these similarities have been produced by other dietary manipulations because feeding cholesterol induces Cu deficiency in animals. The most recent of these to be identified is decreased serum dehydroepiandrosterone. Some concomitant aspects of Cu metabolism and utilisation have been identified in other theories about heart disease: fetal programming, homocysteine, and Fe overload.

Validation and Assessment of Three Methods to Estimate 24-h Urinary Sodium Excretion from Spot Urine Samples in Chinese Adults

24-h urinary sodium excretion is the gold standard for evaluating dietary sodium intake, but it is often not feasible in large epidemiological studies due to high participant burden and cost. Three methods--Kawasaki, INTERSALT, and Tanaka--have been proposed to estimate 24-h urinary sodium excretion from a spot urine sample, but these methods have not been validated in the general Chinese population. This aim of this study was to assess the validity of three methods for estimating 24-h urinary sodium excretion using spot urine samples against measured 24-h urinary sodium excretion in a Chinese sample population. Data are from a substudy of the Prospective Urban Rural Epidemiology (PURE) study that enrolled 120 participants aged 35 to 70 years and collected their morning fasting urine and 24-h urine specimens. Bias calculations (estimated values minus measured values) and Bland-Altman plots were used to assess the validity of the three estimation methods. 116 participants were included in the final analysis. Mean bias for the Kawasaki method was -740 mg/day (95% CI: -1219, 262 mg/day), and was the lowest among the three methods. Mean bias for the Tanaka method was -2305 mg/day (95% CI: -2735, 1875 mg/day). Mean bias for the INTERSALT method was -2797 mg/day (95% CI: -3245, 2349 mg/day), and was the highest of the three methods. Bland-Altman plots indicated that all three methods underestimated 24-h urinary sodium excretion. The Kawasaki, INTERSALT and Tanaka methods for estimation of 24-h urinary sodium excretion using spot urines all underestimated true 24-h urinary sodium excretion in this sample of Chinese adults. Among the three methods, the Kawasaki method was least biased, but was still relatively inaccurate. A more accurate method is needed to estimate the 24-h urinary sodium excretion from spot urine for assessment of dietary sodium intake in China.

Diet-related greenhouse gas emissions assessed by a food frequency questionnaire and validated using 7-day weighed food records

BACKGROUND

The current food system generates about 25 % of total greenhouse gas emissions (GHGE), including deforestation, and thereby substantially contributes to the warming of the earth's surface. To understand the association between food and nutrient intake and GHGE, we therefore need valid methods to assess diet-related GHGE in observational studies.

METHODS

Life cycle assessment (LCA) studies assess the environmental impact of different food items. We linked LCA data expressed as kg carbon dioxide equivalents (CO2e) per kg food product to data on food intake assessed by the food frequency questionnaire (FFQ) Meal-Q and validated it against a 7-day weighed food record (WFR). 166 male and female volunteers aged 20-63 years completed Meal-Q and the WFR, and their food intake was linked to LCA data.

RESULTS

The mean GHGE assessed with Meal-Q was 3.76 kg CO2e per day and person, whereas it was 5.04 kg CO2e using the WFR. The energy-adjusted and deattenuated Pearson and Spearman correlation coefficients were 0.68 and 0.70, respectively. Moreover, compared to the WFR, Meal-Q provided a good ranking ability, with 90 % of the participants classified into the same or adjacent quartile according to their daily average CO2e. The Bland-Altman plot showed an acceptable level of agreement between the two methods and the reproducibility of Meal-Q was high.

CONCLUSIONS

This is the first study validating the assessment of diet-related GHGE by a questionnaire. The results suggest that Meal-Q is a useful tool for studying the link between food habits and CO2e in future epidemiological studies.

FFQ for the adult population of the capital of Ecuador (FFQ-Quito): development, reliability and validity

Objective

To assess the reliability and validity of a semi-quantitative FFQ designed to evaluate the usual nutrient intake of adults in Quito, Ecuador.

Design

Dietary data using 24 h recalls (24hR) were used to design a list of commonly consumed foods. The relative validity of a 111-item FFQ was evaluated by comparing nutrient intakes against three non-consecutive 24hR. All nutrients were energy-adjusted. Reliability was assessed using two FFQ (FFQ1 and FFQ2) and assessed by the intra-class correlation coefficient. The comparisons between the FFQ and the 24hR were assessed by the de-attenuated Pearson correlation coefficient, weighted kappa and by Bland–Altman plots.

Setting

Quito, Ecuador.

Subjects

Overall, 345 adults were enrolled in the present study. Two hundred and fifty participated in FFQ development and ninety-five participated in the FFQ validity and reliability.

Results

The FFQ produced higher energy and nutrient intakes. Reliability correlation coefficients after adjusting for energy ranged from 0·62 to 0·88 for protein and Ca, respectively. For the validity study, energy-adjusted and de-attenuated correlation coefficients between the questionnaire and the 24hR ranged from 0·21 for fat to 0·65 for Ca. Only 4 % of the participants were grossly misclassified and 46 % had weighted kappa higher than 0·42. The Bland–Altman plot showed a constant bias with a tendency to increase according to the intake level.

Conclusions

The FFQ showed reasonably good relative validity and reliable measurements, especially for nutrients considered protective and risk markers of non-communicable disease, and can be used to assess usual nutrient intake in this population.

Relative validity of a semi-quantitative FFQ in 3-year-old Polish children

OBJECTIVES

The aim of the study was to assess the relative validity of a semi-quantitative FFQ (SFFQ) which measures the usual dietary intake of 3-year-old children.

DESIGN

The children's daily dietary intake was measured using the SFFQ. The average intake of three 24 h dietary recalls (24hDR) was calculated as a reference method. Wilcoxon's rank test and Spearman's rank-correlation coefficient were used to compare nutrient intakes assessed by both methods. The level of agreement between the SFFQ and the repeated 24hDR was determined by the Bland-Altman method. To assess the agreement in quartile distribution, the weighted kappa coefficient (κ w) was used.

SETTING

Krakow, Poland.

SUBJECTS

One hundred and forty-three 3-year-old children and their mothers, participants of a prospective cohort study.

RESULTS

Overall, the SFFQ overestimated energy and nutrient intakes compared with the repeated 24hDR. The median correlation coefficient for energy and nutrient intakes was 0·456, with higher results for Ca, P and riboflavin. Although the κ w value showed only slight to fair agreement between the two methods, about 75 % of the children were classified into the same or adjacent quartile and the level of agreement assessed by the Bland-Altman method for most of the nutrients investigated was good.

CONCLUSIONS

The study indicated that the SFFQ might be a useful tool to assess dietary intakes of nutrients by small children, especially for ranking them according their nutrient intake.

Diet pattern and longevity: do simple rules suffice? A commentary

Nutritionism reduces dietary advice to statements about a few nutrients, with sometimes unintended implications for science, industry, and the public. Although reductionist questions about nutrition are legitimate scientifically, a nutrient focus in the public arena forces the food industry to compete with the use of nutrient statements. Consumers must interpret information that may not be correct or relevant. The theory of food synergy, which postulates that the many constituents of individual foods and dietary patterns act together on health, leads to the idea that dietary policy would be clearer if it focused on foods. To illustrate this method, the food-based A Priori Diet Quality Score was described in the Iowa Women's Health Study; a substantial total mortality reduction for increasing quartiles of the score was found. The simple food-based rules implied in this a priori score support minimizing meat, salt, added sugar, and heavily processed foods while emphasizing phytochemical-rich foods. These principles could help improve nutrition policy, help industry to supply better food, and help to focus future scientific research. Although an understanding of what foods are best for health is a step forward in nutrition, other major challenges remain, including getting high-quality food to the masses and food sustainability.

Relative validity of micronutrient and fiber intake assessed with two new interactive meal- and Web-based food frequency questionnaires

BACKGROUND

The meal- and Web-based food frequency questionnaires, Meal-Q and MiniMeal-Q, were developed for cost-efficient assessment of dietary intake in epidemiological studies.

OBJECTIVE

The objective of this study was to evaluate the relative validity of micronutrient and fiber intake assessed with Meal-Q and MiniMeal-Q. The reproducibility of Meal-Q was also evaluated.

METHODS

A total of 163 volunteer men and women aged between 20 and 63 years were recruited from Stockholm County, Sweden. Assessment of micronutrient and fiber intake with the 174-item Meal-Q was compared to a Web-based 7-day weighed food record (WFR). Two administered Meal-Q questionnaires were compared for reproducibility. The 126-item MiniMeal-Q, developed after the validation study, was evaluated in a simulated validation by using truncated Meal-Q data.

RESULTS

The study population consisted of approximately 80% women (129/163) with a mean age of 33 years (SD 12) who were highly educated (130/163, 80% with >12 years of education) on average. Cross-classification of quartiles with the WFR placed 69% to 90% in the same/adjacent quartile for Meal-Q and 67% to 89% for MiniMeal-Q. Bland-Altman plots with the WFR and the questionnaires showed large variances and a trend of increasing underestimation with increasing intakes. Deattenuated and energy-adjusted Spearman rank correlations between the questionnaires and the WFR were in the range ρ=.25-.69, excluding sodium that was not statistically significant. Cross-classifications of quartiles of the 2 Meal-Q administrations placed 86% to 97% in the same/adjacent quartile. Intraclass correlation coefficients for energy-adjusted intakes were in the range of .50-.76.

CONCLUSIONS

With the exception of sodium, this validation study demonstrates Meal-Q and MiniMeal-Q to be useful methods for ranking micronutrient and fiber intake in epidemiological studies with Web-based data collection.

Estimating and testing interactions when explanatory variables are subject to non-classical measurement error

Assessing interactions in linear regression models when covariates have measurement error (ME) is complex.We previously described regression calibration (RC) methods that yield consistent estimators and standard errors for interaction coefficients of normally distributed covariates having classical ME. Here we extend normal based RC (NBRC) and linear RC (LRC) methods to a non-classical ME model, and describe more efficient versions that combine estimates from the main study and internal sub-study. We apply these methods to data from the Observing Protein and Energy Nutrition (OPEN) study. Using simulations we show that (i) for normally distributed covariates efficient NBRC and LRC were nearly unbiased and performed well with sub-study size ≥200; (ii) efficient NBRC had lower MSE than efficient LRC; (iii) the naïve test for a single interaction had type I error probability close to the nominal significance level, whereas efficient NBRC and LRC were slightly anti-conservative but more powerful; (iv) for markedly non-normal covariates, efficient LRC yielded less biased estimators with smaller variance than efficient NBRC. Our simulations suggest that it is preferable to use: (i) efficient NBRC for estimating and testing interaction effects of normally distributed covariates and (ii) efficient LRC for estimating and testing interactions for markedly non-normal covariates.

Measurement error in time-series analysis: a simulation study comparing modelled and monitored data

Background

Assessing health effects from background exposure to air pollution is often hampered by the sparseness of pollution monitoring networks. However, regional atmospheric chemistry-transport models (CTMs) can provide pollution data with national coverage at fine geographical and temporal resolution. We used statistical simulation to compare the impact on epidemiological time-series analysis of additive measurement error in sparse monitor data as opposed to geographically and temporally complete model data.

Methods

Statistical simulations were based on a theoretical area of 4 regions each consisting of twenty-five 5 km × 5 km grid-squares. In the context of a 3-year Poisson regression time-series analysis of the association between mortality and a single pollutant, we compared the error impact of using daily grid-specific model data as opposed to daily regional average monitor data. We investigated how this comparison was affected if we changed the number of grids per region containing a monitor. To inform simulations, estimates (e.g. of pollutant means) were obtained from observed monitor data for 2003–2006 for national network sites across the UK and corresponding model data that were generated by the EMEP-WRF CTM. Average within-site correlations between observed monitor and model data were 0.73 and 0.76 for rural and urban daily maximum 8-hour ozone respectively, and 0.67 and 0.61 for rural and urban log_e(daily 1-hour maximum NO₂).

Results

When regional averages were based on 5 or 10 monitors per region, health effect estimates exhibited little bias. However, with only 1 monitor per region, the regression coefficient in our time-series analysis was attenuated by an estimated 6% for urban background ozone, 13% for rural ozone, 29% for urban background log_e(NO₂) and 38% for rural log_e(NO₂). For grid-specific model data the corresponding figures were 19%, 22%, 54% and 44% respectively, i.e. similar for rural log_e(NO₂) but more marked for urban log_e(NO₂).

Conclusion

Even if correlations between model and monitor data appear reasonably strong, additive classical measurement error in model data may lead to appreciable bias in health effect estimates. As process-based air pollution models become more widely used in epidemiological time-series analysis, assessments of error impact that include statistical simulation may be useful.

Randomized controlled trial of behavioral treatment for comorbid obesity and depression in women: the Be Active Trial

OBJECTIVE

Depression is associated with increased risk for obesity and worse weight loss treatment outcomes. The purpose of the present study was to test the hypothesis that delivering evidence-based behavior therapy for depression before a lifestyle weight loss intervention improves both weight loss and depression.

DESIGN

In a randomized controlled trial, obese women with major depressive disorder (N=161, mean age=45.9 (s.d.: 10.8) years) were randomized to brief behavior therapy for depression treatment followed by a lifestyle intervention (BA) or a lifestyle intervention only (LI). Follow-up occurred at 6 and 12 months. Main outcome measures included weight loss and depression symptoms.

RESULTS

Intention-to-treat analyses revealed both conditions lost significant weight, but no differences between conditions in weight change at 6 months (BA=-3.0%, s.e.=-0.65%; LI=-3.7%, s.e.=0.63%; P=0.48) or 12 months (BA=-2.6%, s.e.=0.77%; LI=-3.1%, s.e.=0.74%; P=0.72). However, the BA condition evidenced significantly greater improvement in Beck Depression Inventory-II scores relative to the LI condition at both 6 months (BA mean change=-12.5, s.d.=0.85; LI mean change=-9.2, s.d.=0.80, P=0.005) and 12 months (BA mean change=-12.6, s.d.=0.97; LI mean change=-9.9, s.d.=0.93; P=0.045). Participants who experienced depression remission by 6 months (61.2%) lost greater weight (mean=-4.31%; s.e.=0.052) than those who did not (39.7%; mean=-2.47%, s.e.=0.53; P=.001).

CONCLUSION

Adding behavior therapy to a lifestyle intervention results in greater depression remission but does not improve weight loss within 1 year. Improvement in depression is associated with greater weight loss.

Mapping low intake of micronutrients across Europe

Achieving an understanding of the extent of micronutrient adequacy across Europe is a major challenge. The main objective of the present study was to collect and evaluate the prevalence of low micronutrient intakes of different European countries by comparing recent nationally representative dietary survey data from Belgium, Denmark, France, Germany, The Netherlands, Poland, Spain and the United Kingdom. Dietary intake information was evaluated for intakes of Ca, Cu, I, Fe, Mg, K, Se, Zn and the vitamins A, B₁, B₂, B₆, B₁₂, C, D, E and folate. The mean and 5th percentile of the intake distributions were estimated for these countries, for a number of defined sex and age groups. The percentages of those with intakes below the lower reference nutrient intake and the estimated average requirement were calculated. Reference intakes were derived from the UK and Nordic Nutrition Recommendations. The impact of dietary supplement intake as well as inclusion of apparently low energy reporters on the estimates was evaluated. Except for vitamin D, the present study suggests that the current intakes of vitamins from foods lead to low risk of low intakes in all age and sex groups. For current minerals, the study suggests that the risk of low intakes is likely to appear more often in specific age groups. In spite of the limitations of the data, the present study provides valuable new information about micronutrient intakes across Europe and the likelihood of inadequacy country by country.

Two new meal- and web-based interactive food frequency questionnaires: validation of energy and macronutrient intake

BACKGROUND

Meal-Q and its shorter version, MiniMeal-Q, are 2 new Web-based food frequency questionnaires. Their meal-based and interactive format was designed to promote ease of use and to minimize answering time, desirable improvements in large epidemiological studies.

OBJECTIVE

We evaluated the validity of energy and macronutrient intake assessed with Meal-Q and MiniMeal-Q as well as the reproducibility of Meal-Q.

METHODS

Healthy volunteers aged 20-63 years recruited from Stockholm County filled out the 174-item Meal-Q. The questionnaire was compared to 7-day weighed food records (WFR; n=163), for energy and macronutrient intake, and to doubly labeled water (DLW; n=39), for total energy expenditure. In addition, the 126-item MiniMeal-Q was evaluated in a simulated validation using truncated Meal-Q data. We also assessed the answering time and ease of use of both questionnaires.

RESULTS

Bland-Altman plots showed a varying bias within the intake range for all validity comparisons. Cross-classification of quartiles placed 70%-86% in the same/adjacent quartile with WFR and 77% with DLW. Deattenuated and energy-adjusted Pearson correlation coefficients with the WFR ranged from r=0.33-0.74 for macronutrients and was r=0.18 for energy. Correlations with DLW were r=0.42 for Meal-Q and r=0.38 for MiniMeal-Q. Intraclass correlations for Meal-Q ranged from r=0.57-0.90. Median answering time was 17 minutes for Meal-Q and 7 minutes for MiniMeal-Q, and participants rated both questionnaires as easy to use.

CONCLUSIONS

Meal-Q and MiniMeal-Q are easy to use and have short answering times. The ranking agreement is good for most of the nutrients for both questionnaires and Meal-Q shows fair reproducibility.

Quantifying diet for nutrigenomic studies

The field of nutrigenomics shows tremendous promise for improved understanding of the effects of dietary intake on health. The knowledge that metabolic pathways may be altered in individuals with genetic variants in the presence of certain dietary exposures offers great potential for personalized nutrition advice. However, although considerable resources have gone into improving technology for measurement of the genome and biological systems, dietary intake assessment remains inadequate. Each of the methods currently used has limitations that may be exaggerated in the context of gene × nutrient interaction in large multiethnic studies. Because of the specificity of most gene × nutrient interactions, valid data are needed for nutrient intakes at the individual level. Most statistical adjustment efforts are designed to improve estimates of nutrient intake distributions in populations and are unlikely to solve this problem. An improved method of direct measurement of individual usual dietary intake that is unbiased across populations is urgently needed.

Appropriateness of the probability approach with a nutrient status biomarker to assess population inadequacy: a study using vitamin D

BACKGROUND

There are questions about the appropriate method for the accurate estimation of the population prevalence of nutrient inadequacy on the basis of a biomarker of nutrient status (BNS).

OBJECTIVE

We determined the applicability of a statistical probability method to a BNS, specifically serum 25-hydroxyvitamin D [25(OH)D]. The ability to meet required statistical assumptions was the central focus.

DESIGN

Data on serum 25(OH)D concentrations in adults aged 19-70 y from the 2005-2006 NHANES were used (n = 3871). An Institute of Medicine report provided reference values. We analyzed key assumptions of symmetry, differences in variance, and the independence of distributions. We also corrected observed distributions for within-person variability (WPV). Estimates of vitamin D inadequacy were determined.

RESULTS

We showed that the BNS [serum 25(OH)D] met the criteria to use the method for the estimation of the prevalence of inadequacy. The difference between observations corrected compared with uncorrected for WPV was small for serum 25(OH)D but, nonetheless, showed enhanced accuracy because of correction. The method estimated a 19% prevalence of inadequacy in this sample, whereas misclassification inherent in the use of the more traditional 97.5th percentile high-end cutoff inflated the prevalence of inadequacy (36%).

CONCLUSIONS

When the prevalence of nutrient inadequacy for a population is estimated by using serum 25(OH)D as an example of a BNS, a statistical probability method is appropriate and more accurate in comparison with a high-end cutoff. Contrary to a common misunderstanding, the method does not overlook segments of the population. The accuracy of population estimates of inadequacy is enhanced by the correction of observed measures for WPV.

Determinants of plasma 25-hydroxyvitamin D and development of prediction models in three US cohorts

Epidemiological and other evidence suggests that vitamin D may be protective against several chronic diseases. Assessing vitamin D status in epidemiological studies, however, is challenging given finite resources and limitations of commonly used approaches. Using multivariable linear regression, we derived predicted 25-hydroxyvitamin D (25(OH)D) scores based on known determinants of circulating 25(OH)D, including age, race, UV-B radiation flux at residence, dietary and supplementary vitamin D intakes, BMI, physical activity, alcohol intake, post-menopausal hormone use (women only) and season of blood draw, in three nationwide cohorts: the Nurses' Health Study, Nurses' Health Study II and the Health Professionals Follow-up Study. The model r 2 for each cohort ranged from 0·25 to 0·33. We validated the prediction models in independent samples of participants from these studies. Mean measured 25(OH)D levels rose with increasing decile of predicted 25(OH)D score, such that the differences in mean measured 25(OH)D between the extreme deciles of predicted 25(OH)D were in the range 8·7-12·3 ng/ml. Substituting predicted 25(OH)D scores for measured 25(OH)D in a previously published case-control analysis of colorectal cancer yielded similar effect estimates with OR of approximately 0·8 for a 10 ng/ml difference in either plasma or predicted 25(OH)D. We conclude that these data provide reasonable evidence that a predicted 25(OH)D score is an acceptable marker for ranking individuals by long-term vitamin D status and may be particularly useful in research settings where biomarkers are not available for the majority of a study population.

Exposure to inhalable dust and endotoxin among Danish livestock farmers: results from the SUS cohort study

Studies on personal dust and endotoxin concentrations among animal farmers have been either small or limited to a few sectors in their investigations. The present study aimed to provide comparable information on the levels and variability of exposure to personal dust and endotoxin in different types of animal farmers. 507 personal inhalable dust samples were collected from 327 farmers employed in 54 pig, 26 dairy, 3 poultry, and 3 mink farms in Denmark. Measurements in pig and dairy farmers were full-shift and performed during summer and winter, while poultry and mink farmers were monitored during 4 well-defined production stages. The collected samples were measured for dust gravimetrically and analyzed for endotoxin by the Limulus amebocyte lysate assay. Simple statistics and random-effect analysis were used to describe the levels and the variability in measured dust and endotoxin exposure concentrations. Measured inhalable dust levels had an overall geometric mean of 2.5 mg m(-3) (range <LOD to 47.8) and endotoxin of 988 EU m(-3) (range <LOD to 374,000). The highest dust and endotoxin concentrations were measured among pig and poultry farmers, and were the lowest among dairy and mink farmers, respectively. Exposure among pig and cattle farmers was characterised by a substantial day-to-day variability that increased from the indoor to outdoor working environment. Only mink farmers complied with the Danish occupational exposure limit for total dust (3 mg m(-3)). More than 93% of our measurements exceeded the recently proposed Dutch exposure-limit for endotoxin (90 EU m(-3)). These findings suggest animal farmers to be exposed to high levels of dust and endotoxin consistent with an increased risk of developing respiratory symptoms and diseases. The development of preventive strategies to reduce exposure will require in-depth identification of factors that affect day-to-day variability in exposure.

A moment-adjusted imputation method for measurement error models

Studies of clinical characteristics frequently measure covariates with a single observation. This may be a mismeasured version of the "true" phenomenon due to sources of variability like biological fluctuations and device error. Descriptive analyses and outcome models that are based on mismeasured data generally will not reflect the corresponding analyses based on the "true" covariate. Many statistical methods are available to adjust for measurement error. Imputation methods like regression calibration and moment reconstruction are easily implemented but are not always adequate. Sophisticated methods have been proposed for specific applications like density estimation, logistic regression, and survival analysis. However, it is frequently infeasible for an analyst to adjust each analysis separately, especially in preliminary studies where resources are limited. We propose an imputation approach called moment-adjusted imputation that is flexible and relatively automatic. Like other imputation methods, it can be used to adjust a variety of analyses quickly, and it performs well under a broad range of circumstances. We illustrate the method via simulation and apply it to a study of systolic blood pressure and health outcomes in patients hospitalized with acute heart failure.

Arguments at mealtime and child energy intake

OBJECTIVE

To examine how arguments at mealtimes relate to children's daily energy intake.

DESIGN

A cross-sectional study using data obtained through the Québec Longitudinal Study of Child Development 1998-2010 (QLSCD), a representative sample of children born in 1998, in the province of Québec, Canada.

SETTING

Face-to-face interviews, questionnaires, and 24-hour dietary recall interviews addressed to children's parents.

PARTICIPANTS

One thousand five hundred forty-nine 4-year-old children who participated in a nutrition substudy.

MAIN OUTCOME MEASURE

Children's energy intakes were measured through a 24-hour dietary recall interview administered to parents by trained nutritionists, in the children's homes.

ANALYSIS

The main associations were examined through chi-square tests of independence and through multivariate logistic regression analyses.

RESULTS

The adjusted odds for consuming a high daily energy intake was 2.5 (95% confidence interval: 1.3-4.9) in children who were never exposed to arguments (between parents and children) at mealtimes, in comparison to children who were often or always exposed to arguments.

CONCLUSIONS AND IMPLICATIONS

Mealtimes that are free of arguments, specifically between parents and children, appear to associate with high daily energy intakes in children, even after controlling for other factors, including a child's level of physical activity, eating in front of the television, mother's educational level, and number of overweight parents, among others.

Higher intakes of energy and grain products at 4 years of age are associated with being overweight at 6 years of age

This study examined dietary factors associated with overweight in a population-based sample of 6-y-old children. Analyses of data from the Québec Longitudinal Study of Child Development (QLSCD) included a representative sample (n = 1014) of children born in 1998 in the province of Québec, Canada. Dietary intake was measured by using a 24-h dietary recall administered at 4 y of age. Weight and height were measured using a standard protocol at 6 y. Using logistic regression, higher daily energy intake at 4 y was significantly related to overweight at 6 y. After adjustment for confounding and overweight at 4 y, the relationship remained significant among girls (P = 0.04) but became marginally significant among boys (P = 0.07). Additionally, boys who consumed ≥5 servings of grain products/d at 4 y were more likely to be overweight at 6 y compared to those who did not [adjusted OR = 3.20 (95% CI): 1.72-5.97]. The association attenuated somewhat after adjustment for overweight at 4 y [OR = 1.82 (95% CI): 0.894-3.71; P = 0.09]. The findings provide support for the revisions made in the Canadian dietary guidelines for young children, which now recommend 4-7 servings of grain products daily for children aged 4-8 y rather than the excessive 5-12 servings of previous recommendations.

Organophosphate pesticide metabolite levels in pre-school children in an agricultural community: within- and between-child variability in a longitudinal study

This study characterized the within- and between-child variability in dimethylthiophosphate (DMTP) levels in the urine of 44 children living in an agricultural community in central Washington State in December 1997 and 1999. The goal of this analysis was to investigate these variability components during periods when organophosphate pesticides were and were not actively applied to orchards in that community. Each child provided between 10 and 26 biweekly urine samples over a 21-month period, and these samples were analyzed for six dialkylphosphate (DAP) metabolites common to organophosphate pesticides, including DMTP. Previous analysis of this dataset found that DAP concentrations were elevated during months when organophosphate pesticides were applied to orchards in this region. The current analysis demonstrates that the within-child component of day-to-day variability was much greater than the between-child component of variability by a factor of 3-7 across the DAP metabolites that were analyzed. Therefore, organophosphate pesticide exposure appeared to vary more than 3 times from day-to-day than from child-to-child. This finding has important implications for epidemiologic and exposure pathways research, since accounting for within-child variability may increase the power of a study and allow for the detection of differences that would not otherwise be possible without an analysis that separates out the within-child variability.

Review of pesticide urinary biomarker measurements from selected US EPA children's observational exposure studies

Children are exposed to a wide variety of pesticides originating from both outdoor and indoor sources. Several studies were conducted or funded by the EPA over the past decade to investigate children’s exposure to organophosphate and pyrethroid pesticides and the factors that impact their exposures. Urinary metabolite concentration measurements from these studies are consolidated here to identify trends, spatial and temporal patterns, and areas where further research is required. Namely, concentrations of the metabolites of chlorpyrifos (3,5,6-trichloro-2-pyridinol or TCPy), diazinon (2-isopropyl-6-methyl-4-pyrimidinol or IMP), and permethrin (3-phenoxybenzoic acid or 3-PBA) are presented. Information on the kinetic parameters describing absorption and elimination in humans is also presented to aid in interpretation. Metabolite concentrations varied more dramatically across studies for 3-PBA and IMP than for TCPy, with TCPy concentrations about an order of magnitude higher than the 3-PBA concentrations. Temporal variability was high for all metabolites with urinary 3-PBA concentrations slightly more consistent over time than the TCPy concentrations. Urinary biomarker levels provided only limited evidence of applications. The observed relationships between urinary metabolite levels and estimates of pesticide intake may be affected by differences in the contribution of each exposure route to total intake, which may vary with exposure intensity and across individuals.

Demographic and socio-economic factors related to food intake and adherence to nutritional recommendations in a cohort of pre-school children

Objective

To examine: (i) children's food intake and adherence to both Canada's Food Guide for Healthy Eating and Dietary Reference Intakes; and (ii) the social and demographic factors related to children's food intake.

Design

A cross-sectional study.

Setting

Data were obtained through the Quebec Longitudinal Study of Child Development 1998–2010, a representative sample (n 2103) of children born in 1998 in the province of Quebec, Canada. Information on energy, macronutrient and food consumption was derived from responses to a 24 h dietary recall interview addressed to children's mothers and day-care staff when the children were 4 years old.

Subjects

A total of 1549 children aged 4 years who participated in a nutritional sub-study.

Results

The mean daily total energy intake was 6360 kJ (1520 kcal) for girls and 6916 kJ (1653 kcal) for boys. For boys and girls alike, energy intake was comprised of approximately 54 % carbohydrates, 31 % fats and 15 % proteins. The mean number of servings consumed from each of the four essential food groups closely approached the dietary recommendations made by Canada's Food Guide for Healthy Eating; however, <2 % of the children in the present study actually met the full dietary guidelines. The dietary intake of pre-school children was associated with socio-economic and demographic factors, most notably mother's level of education, mother's immigrant status and sex of the child.

Conclusions

Diet-related disparities associated with socio-economic and demographic factors exist from as early as 4 years of age.

Exclusive breastfeeding duration and later intake of vegetables in preschool children

BACKGROUND/OBJECTIVES

To examine whether a relationship exists between exclusive breastfeeding duration and later vegetable consumption in 4-year-old children, independently of factors traditionally associated with children's vegetable intake.

SUBJECTS/METHODS

A longitudinal study using information collected on children's food consumption patterns and behaviors from a representative sample of children born in 1998 in the province of Québec, Canada. Face-to-face interviews and self-administered questionnaires were addressed to children's mothers and fathers. From the first group of children (n=2100) included in the cohort, a subsample of 4-year-old children participated in a nutrition substudy (n=1549).

RESULTS

Children whose mothers held a university degree had odds of 8.7 (95% CI: 4.23-17.93) for consuming two or more servings of vegetables a day at 4 years of age (vs less than one serving per day) in comparison to children of mothers with no high school diploma. Likewise, children who were exclusively breastfed for 3 or more months had odds of 2.6 (95% CI: 1.34-5.02, with 3 to <4 months of exclusive breastfeeding) and 1.9 (95% CI: 1.01-3.61, with 4 or more months of exclusive breastfeeding) for consuming two or more servings of vegetables per day (vs less than one serving per day) in comparison to children who were formula-fed and/or partially breastfed (no exclusive breastfeeding).

CONCLUSIONS

The findings suggest that three or more months of exclusive breastfeeding is a predictive factor for higher vegetable consumption in preschool children.