An approach to estimate between- and within-group correlation coefficients in multicenter studies: plasma carotenoids as biomarkers of intake of fruits and vegetables

FirstStep2Health: A cluster randomised trial to promote healthy behaviours and prevent obesity amongst low-income preschoolers

OBJECTIVE

To evaluate the preliminary effects of a theory-based, multi-component intervention on improving healthy lifestyle behaviours and preventing obesity amongst low-income preschoolers.

METHODS

A cluster randomised controlled trial was conducted at 10 daycare centres. The 16-week FirstStep2Health intervention, grounded in the Actor-Partner Interdependence Model and the Social Cognitive Theory, included five components: a Facebook-based parent programme, three virtual parent meetings, three weekly motivational text messages, parent-child learning via weekly child letters and daycare centre-based child programme.

RESULTS

A total of 95 preschoolers (53 intervention and 42 control) participated. Preschoolers' mean age was 49.27 months, with 57.9% being female, 12.6% being Hispanic and 40% being African American. The intervention significantly decreased intervention preschoolers' fat intake (B = -33.76, p = 0.047) and % body fat (B = -1.18, p = 0.036) compared to the control. During year 2, there were significant intervention effects on increasing skin carotenoids (B = 87.06, p = 0.035). Although not statistically significant, the intervention showed positive effects on increasing preschoolers' fruit/vegetable intake; and decreasing screen time, body mass index z-score and proportion of overweight/obesity.

CONCLUSIONS

Even with some potential limitations (small sample size, measurement concerns and confounding with Coronavirus Disease 2019 pandemic), the study's results support the preliminary efficacy of the FirstStep2Health intervention in preventing obesity amongst low-income racially diverse preschoolers.

Happy Family, Healthy Kids: A Healthy Eating and Stress Management Program in Low-Income Parent-Preschooler Dyads

BACKGROUND

Substantial effort has been invested to combat childhood obesity, but overall effects are disappointing, especially in low-income racial minority children. One possible reason is a lack of focus on the important stress-eating connection. Stress can negatively influence eating behaviors, leading to an increased appetite for high-fat and energy-dense foods.

OBJECTIVE

This study aimed to evaluate the preliminary effects of a healthy eating and stress management program targeting multiple theoretical variables on improving eating behavior (dyads' fruit/vegetable intake, emotional eating), food insecurity, anthropometric characteristics (dyads' body mass index, % body fat), cardiovascular health (dyads' blood pressure), and mental well-being (parental stress).

METHODS

A one-group, quasi-experimental pilot study was conducted among 107 low-income parent-preschooler dyads. The 14-week program included a parent component, a parent-preschooler learning component, and a day care-based preschooler component.

RESULTS

The program had positive effects on improving dyads' fruit/vegetable intake, food insecurity, body mass index, and blood pressure and parents' nutrition knowledge, self-efficacy, support, food resource management behavior, problem-focused coping, and home eating environment. The overall satisfaction rate was 95.2%, and 88.1% stated that the program assisted their families with having a healthy lifestyle.

DISCUSSION

Results support the preliminary effects of the program on improving health outcomes in rural and urban low-income families. Although warranting further investigation with a more rigorous randomized controlled trial, the healthy eating and stress management program provides a potential solution to the current coexistence of an obesity epidemic and mental health crisis.

Dietary biomarkers-an update on their validity and applicability in epidemiological studies

The aim of this literature review was to identify and provide a summary update on the validity and applicability of the most promising dietary biomarkers reflecting the intake of important foods in the Western diet for application in epidemiological studies. Many dietary biomarker candidates, reflecting intake of common foods and their specific constituents, have been discovered from intervention and observational studies in humans, but few have been validated. The literature search was targeted for biomarker candidates previously reported to reflect intakes of specific food groups or components that are of major importance in health and disease. Their validity was evaluated according to 8 predefined validation criteria and adapted to epidemiological studies; we summarized the findings and listed the most promising food intake biomarkers based on the evaluation. Biomarker candidates for alcohol, cereals, coffee, dairy, fats and oils, fruits, legumes, meat, seafood, sugar, tea, and vegetables were identified. Top candidates for all categories are specific to certain foods, have defined parent compounds, and their concentrations are unaffected by nonfood determinants. The correlations of candidate dietary biomarkers with habitual food intake were moderate to strong and their reproducibility over time ranged from low to high. For many biomarker candidates, critical information regarding dose response, correlation with habitual food intake, and reproducibility over time is yet unknown. The nutritional epidemiology field will benefit from the development of novel methods to combine single biomarkers to generate biomarker panels in combination with self-reported data. The most promising dietary biomarker candidates that reflect commonly consumed foods and food components for application in epidemiological studies were identified, and research required for their full validation was summarized.

A New Pipeline for the Normalization and Pooling of Metabolomics Data

Pooling metabolomics data across studies is often desirable to increase the statistical power of the analysis. However, this can raise methodological challenges as several preanalytical and analytical factors could introduce differences in measured concentrations and variability between datasets. Specifically, different studies may use variable sample types (e.g., serum versus plasma) collected, treated, and stored according to different protocols, and assayed in different laboratories using different instruments. To address these issues, a new pipeline was developed to normalize and pool metabolomics data through a set of sequential steps: (i) exclusions of the least informative observations and metabolites and removal of outliers; imputation of missing data; (ii) identification of the main sources of variability through principal component partial R-square (PC-PR2) analysis; (iii) application of linear mixed models to remove unwanted variability, including samples' originating study and batch, and preserve biological variations while accounting for potential differences in the residual variances across studies. This pipeline was applied to targeted metabolomics data acquired using Biocrates AbsoluteIDQ kits in eight case-control studies nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Comprehensive examination of metabolomics measurements indicated that the pipeline improved the comparability of data across the studies. Our pipeline can be adapted to normalize other molecular data, including biomarkers as well as proteomics data, and could be used for pooling molecular datasets, for example in international consortia, to limit biases introduced by inter-study variability. This versatility of the pipeline makes our work of potential interest to molecular epidemiologists.

From carotenoid intake to carotenoid blood and tissue concentrations - implications for dietary intake recommendations

There is uncertainty regarding carotenoid intake recommendations, because positive and negative health effects have been found or are correlated with carotenoid intake and tissue levels (including blood, adipose tissue, and the macula), depending on the type of study (epidemiological vs intervention), the dose (physiological vs supraphysiological) and the matrix (foods vs supplements, isolated or used in combination). All these factors, combined with interindividual response variations (eg, depending on age, sex, disease state, genetic makeup), make the relationship between carotenoid intake and their blood/tissue concentrations often unclear and highly variable. Although blood total carotenoid concentrations <1000 nmol/L have been related to increased chronic disease risk, no dietary reference intakes (DRIs) exist. Although high total plasma/serum carotenoid concentrations of up to 7500 nmol/L are achievable after supplementation, a plateauing effect for higher doses and prolonged intake is apparent. In this review and position paper, the current knowledge on carotenoids in serum/plasma and tissues and their relationship to dietary intake and health status is summarized with the aim of proposing suggestions for a "normal," safe, and desirable range of concentrations that presumably are beneficial for health. Existing recommendations are likewise evaluated and practical dietary suggestions are included.

Fruits and vegetables: measuring intake and encouraging increased consumption

A high intake of fruit and vegetables (FV) is associated with reduced risk of chronic disease, although the evidence base is mostly observational. Blood biomarkers offer an objective indicator of FV intake, potentially improving estimates of intakes based on traditional methods. A valid biomarker of overall FV intake would be able to confirm population intakes, more precisely evaluate the association between intakes and health outcomes and confirm compliance in FV interventions. Several substances have been proposed as biomarkers of FV intake: vitamin C, the carotenoids and polyphenols. Certain biomarkers are strong predictors of single FV; however, the proposed single biomarkers of FV consumption are only modestly predictive of overall FV consumption. This is likely to be due to the complexity of the FV food group. While accurately measuring FV intake is important in nutrition research, another critical question is: how best can an increase in FV intake be achieved? Increased FV intake has been achieved in efficacy studies using intensive dietary advice. Alternative, less intensive methods for encouraging FV consumption need to be developed and tested for population level intervention. Systematic reviews suggest peer support to be an effective strategy to promote dietary change. This review will describe the evidence for a link between increased FV intake and good health, outline possible novel biomarkers of FV consumption, present the most recently available data on population intake of FV and examine the usefulness of different approaches to encourage increased consumption of FV.

Challenges in estimating the validity of dietary acrylamide measurements

BACKGROUND

Acrylamide is a chemical compound present in tobacco smoke and food, classified as a probable human carcinogen and a known human neurotoxin. Acrylamide is formed in foods, typically carbohydrate-rich and protein-poor plant foods, during high-temperature cooking or other thermal processing. The objectives of this study were to compare dietary estimates of acrylamide from questionnaires (DQ) and 24-h recalls (R) with levels of acrylamide adduct (AA) in haemoglobin.

METHODS

In the European Prospective Investigation into Cancer and Nutrition (EPIC) study, acrylamide exposure was assessed in 510 participants from 9 European countries, randomly selected and stratified by age, sex, with equal numbers of never and current smokers. After adjusting for country, alcohol intake, smoking status, number of cigarettes and energy intake, correlation coefficients between various acrylamide measurements were computed, both at the individual and at the aggregate (centre) level.

RESULTS

Individual level correlation coefficient between DQ and R measurements (r DQ,R) was 0.17, while r DQ,AA and r R,AA were 0.08 and 0.06, respectively. In never smokers, r DQ,R, r DQ,AA and r R,AA were 0.19, 0.09 and 0.02, respectively. The correlation coefficients between means of DQ, R and AA measurements at the centre level were larger (r > 0.4).

CONCLUSIONS

These findings suggest that estimates of total acrylamide intake based on self-reported diet correlate weakly with biomarker AA Hb levels. Possible explanations are the lack of AA levels to capture dietary acrylamide due to individual differences in the absorption and metabolism of acrylamide, and/or measurement errors in acrylamide from self-reported dietary assessments, thus limiting the possibility to validate acrylamide DQ measurements.

Strength of the relationships between three self-reported dietary intake instruments and serum carotenoids: the Observing Energy and Protein Nutrition (OPEN) Study

Objective

To assess the strength of the relationships between serum carotenoids and three self-reported dietary intake instruments often used to characterize carotenoid intake in studies of diet and disease.

Design

Participants completed a Diet History Questionnaire (DHQ), two 24 h dietary recalls (24HR), a fruit and vegetable screener and a fasting blood draw. We derived dietary intake estimates of α-carotene, β-carotene, cryptoxanthin, lutein, zeaxanthin and lycopene from each diet instrument and calculated sex-specific multivariate correlations between dietary intake estimates and their corresponding serum values.

Setting

Montgomery County, Maryland, USA.

Subjects

Four hundred and seventy women and men aged 40–69 years in the National Cancer Institute's Observing Protein and Energy Nutrition (OPEN) Study.

Results

Serum carotenoids correlated more strongly with the DHQ (r = 0·34–0·54 for women; r = 0·38–0·56 for men) than with the average of two recalls (r = 0·26–0·47 for women; r = 0·26–0·40 for men) with the exception of zeaxanthin, for which the correlations using recalls were higher. With adjustment for within-person variation, correlations between serum carotenoids and recalls were greatly improved (r = 0·38–0·83 for women; r = 0·42–0·74 for men). In most cases, correlations between serum carotenoids and the fruit and vegetable screener resembled serum–DHQ correlations.

Conclusions

Evidence from the study provides support for the use of the DHQ, a fruit and vegetable screener and deattenuated recalls for estimating carotenoid status in studies without serum measures, and draws attention to the importance of adjusting for intra-individual variability when using recalls to estimate carotenoid values.

The association between alcohol consumption patterns and adherence to food consumption guidelines

OBJECTIVE

To examine the association between alcohol consumption patterns and adherence to major food consumption guidelines in adults in Spain.

METHODS

Telephone survey of 12,037 persons, representative of the population age 18 to 64 years in the region of Madrid, conducted from 2000 to 2005. The threshold between average moderate and excessive drinking was 40 g alcohol/d in men and 24 g/d in women. Binge drinking was defined as intake of ≥80 g alcohol in men and ≥60 g in women during 1 drinking session in the last 30 days. Food consumption was measured with a 24-hour recall. Statistical analyses were performed using logistic regression and adjusted for the main confounders.

RESULTS

In total, 4.3% of study participants were excessive drinkers and 10.3% binge drinkers; 6.5% preferred spirits and 24.2% drank with meals. In comparison with never drinking, average moderate drinking with binge drinking was associated with excessive meat consumption (>1 serving/d). Excessive alcohol consumption without binge drinking was associated with insufficient intake of milk products (<2 servings/d) and excessive consumption of meat, fish, and eggs (>2 servings/d). Excessive drinkers with binge drinking more often did not meet the guidelines on consumption of fruit and vegetables (<3 servings/d), milk products, and meat. Excessive drinkers, with and without binge drinking, were more likely to skip a meal, especially breakfast. Consumption mainly of spirits was associated with insufficient fruit and vegetable consumption, and with skipping a meal. Finally, drinking at mealtimes was associated with poor adherence to most of the food consumption guidelines. No dietary differences between men and women were found in relation to alcohol consumption.

CONCLUSIONS

Average excessive alcohol consumption, binge drinking, preference for spirits, and drinking alcohol at mealtimes are associated with poor adherence to major food consumption guidelines.

Components of variation in serum carotenoid concentrations: the Polyp Prevention Trial

OBJECTIVES

The intra- and interindividual variations and season and center effects were estimated from a series of serum carotenoid concentrations in the Polyp Prevention Trial (PPT) participants.

SUBJECTS/METHODS

Fasting blood was collected annually for 4 years in all 1905 participants, and a subcohort of 901 participants were selected within each (of eight) center(s), by gender and dietary arm of the study, for measurement of five major carotenoid peaks. Using variance of component methods, the variation in serum carotenoid concentrations about the underlying mean was partitioned into explanatory components attributed to various sources.

RESULTS

The contributions of the inter- and intraindividual variances to the overall variation in carotenoid concentrations were in the range of 61-70 and 20-35%, respectively, whereas center and center-by-season effects provided 2.6-9.5 and 0.2-1.4%, respectively. The highest percent (35%) of intraindividual variation was exhibited by lycopene, and the highest percent (70% apiece) of interindividual variation was exhibited by lutein/zeaxanthin and beta-carotene. Serum lycopene had the highest ratio of intra- to interindividual variation of 0.57, whereas lutein had the lowest ratio of 0.29. We estimate that the ratio of intra- to interindividual variance around the mean carotenoid concentration can be reduced greatly by collecting 3-4 compared to 1 blood measurement in large-scale trials like the PPT.

CONCLUSION

In the largest study of components of variation in individuals at high risk for colorectal cancer, the largest contributors to variation in serum carotenoid concentrations were intra- and interindividual effects followed by center and center-by-season effects.

DNA damage, a biomarker of carcinogenesis: its measurement and modulation by diet and environment

Free radicals and other reactive oxygen or nitrogen species are constantly generated in vivo and can cause oxidative damage to DNA. This damage has been implicated to be important in many diseases, including cancer. The assessment of damage in various biological matrices, such as tissues, cells, and urine, is vital to understanding this role and subsequently devising intervention strategies. During the last 20 years, many analytical techniques have been developed to monitor oxidative DNA base damage. High-performance liquid chromatography-electrochemical detection and gas chromatography-mass spectrometry are the two pioneering contributions to the field. Currently, the arsenal of methods available include the promising high-performance liquid chromatography-tandem mass spectrometry technique, capillary electrophoresis, 32P-postlabeling, antibody-base immunoassays, and assays involving the use of DNA repair glycosylases such as the comet assay. The objective of this review is to discuss the biological significance of oxidative DNA damage, evaluate the effectiveness of several techniques for measurement of oxidative DNA damage in various biological samples and review current research on factors (dietary and non-dietary) that influence DNA oxidative damage using these techniques.