Nutritional epidemiology: New perspectives for understanding the diet-disease relationship?

The Importance and Challenges of Dietary Intervention Trials for Inflammatory Bowel Disease

Inflammatory bowel disease is believed to be caused by a combination of genetic and environmental stimuli such as our diet. Diets high in meat and fats and low in fruits and vegetables have been associated with new-onset inflammatory bowel disease. This has triggered interest in using dietary modification as a treatment. The 3 principle models of dietary intervention are supplementation with selected dietary components, exclusion of selected dietary components, or use of dietary formulas in place of a normal diet. Despite the high level of interest in dietary interventions as a treatment for inflammatory bowel disease, few well-designed clinical trials have been conducted to firmly establish the optimal diet to induce or maintain remission. This may be in part related to the challenges of conducting dietary intervention trials. This review examines these challenges and potential approaches to be used in dietary intervention trials.

Development and Evaluation of e-CA, an Electronic Mobile-Based Food Record

Measures that capture diet as validly and reliably as possible are cornerstones of nutritional research, and mobile-based devices offer new opportunities to improve and simplify data collection. The balance between precision and acceptability of these data collection tools remains debated, and rigorous validations are warranted. Our objective was to develop and evaluate an electronic mobile-based food record for a research setting. We developed e-CA, which includes almost 900 foods and beverages classified in 14 categories and 60 subcategories. e-CA was evaluated using three different methods: (1) usability and acceptability through a logbook and qualitative interviews; (2) dietary intake accuracy through comparison with 2 unannounced 24-h phone recalls on overlapping days; and (3) reliability and process comparison with a paper-based food record in a laboratory setting with a randomized design. e-CA proved to be intuitive and practical and was perceived as modern, trendy, and fun. Comparisons of e-CA with 24-h telephone recalls or paper-based food records in a laboratory setting with two small convenient samples showed good agreement but highlighted the well-known difficulty of estimating portion sizes and a necessary learning time to use the app. e-CA is a functional tool that has the potential to facilitate food intake measurement for research by increasing the pleasure of using the food record tool and reducing the perceived burden for the participants. It also decreases the workload, costs and the risk of transcription errors for researchers.

Healthy-eating attitudes and the incidence of cardiovascular disease: the SUN cohort

There is an emerging use of brief dietary questionnaires to investigate diet-health relation. We prospectively assess the association between eating attitudes (yes/no) and incident cardiovascular disease (CVD) in 19,138 participants of the Seguimiento Universidad de Navarra (SUN) Cohort. We calculated a baseline healthy-eating attitudes score (in quartiles), positively weighting answers on more fruit, vegetables, fish and fiber and less meat, sweets and pastries, fat, butter, fatty meats and added sugar in drinks. We observed 139 incident cases of CVD. A higher score was associated with a lower risk of CVD [3-5 points Hazard Ratio (HR): 0.38 (95% confidence interval: 0.18-0.81); 6-8 points: 0.57 (0.29-1.12); 9-10 points: 0.31 (0.15-0.67), compared to 0-2 points]. Key contributors were the attitude to increase fruit [HR: 0.59 (0.40-0.87)], vegetables [HR: 0.57 (0.29-1.12)] and fiber intake [HR: 0.69 (0.48-0.98)]. Brief questionnaire on attitudes towards healthy-eating may be a useful tool for the primary prevention of CVD.

Why Are Omics Technologies Important to Understanding the Role of Nutrition in Inflammatory Bowel Diseases?

For many years, there has been confusion about the role that nutrition plays in inflammatory bowel diseases (IBD). It is apparent that good dietary advice for one individual may prove inappropriate for another. As with many diseases, genome-wide association studies across large collaborative groups have been important in revealing the role of genetics in IBD, with more than 200 genes associated with susceptibility to the disease. These associations provide clues to explain the differences in nutrient requirements among individuals. In addition to genes directly involved in the control of inflammation, a number of the associated genes play roles in modulating the gut microbiota. Cell line models enable the generation of hypotheses as to how various bioactive dietary components might be especially beneficial for certain genetic groups. Animal models are necessary to mimic aspects of the complex aetiology of IBD, and provide an important link between tissue culture studies and human trials. Once we are sufficiently confident of our hypotheses, we can then take modified diets to an IBD population that is stratified according to genotype. Studies in IBD patients fed a Mediterranean-style diet have been important in validating our hypotheses and as a proof-of-principle for the application of these sensitive omics technologies to aiding in the control of IBD symptoms.

Consumption of citrus and cruciferous vegetables with incident type 2 diabetes mellitus based on a meta-analysis of prospective study

BACKGROUND

Observational studies and meta-analyses suggested that increased total fruits and vegetables consumption have a protective role in incidence of type 2 diabetes mellitus (T2DM). However, we still don't know whether the subtypes, such as citrus fruits and cruciferous vegetables (CV), have a preventive role.

METHODS

We systematically searched the MEDLINE and EMBASE databases up to December 31, 2014. Summary relative risks (SRRs) and 95% confidence intervals (CIs) were calculated using random-effects models.

RESULTS

Seven distinct prospective cohort studies (five articles) were identified for this study. A total of 16,544 incident cases of type 2 diabetes were ascertained among 306,723 participants with follow-up periods ranging from 4.6 to 24 years. Based on four prospective cohort studies, we found that overall, consumption of CV had a protective role in the T2DM incidence (highest vs. lowest analysis: SRR=0.84, 95% CI: 0.73 to 0.96), with evidence of significant heterogeneity (P=0.09, I(2)=54.4%). This association was independent of the main risk factors for cardiovascular disease: smoking, alcohol use, BMI, and physical activity etc. Consumption of citrus fruits did not have a protective role in the T2DM development (highest vs. lowest analysis: SRR=1.02, 95% CI: 0.96 to 1.08), with no evidence of significant heterogeneity (P=0.49, I(2)=0).

CONCLUSIONS

Higher consumption of CV, but not citrus fruits, is associated with a significantly decreased risk of type 2 diabetes. Further large prospective studies are needed to elucidate both relationships.

Consumption of whole grains in relation to mortality from all causes, cardiovascular disease, and diabetes: Dose-response meta-analysis of prospective cohort studies

BACKGROUND

To investigate the correlation between consumption of whole grains and the risk of all-cause, cardiovascular disease (CVD), and diabetes-specific mortality according to a dose-response meta-analysis of prospective cohort studies.

METHODS

Observational cohort studies, which reported associations between whole grains and the risk of death outcomes, were identified by searching articles in the MEDLINE, EMBASE, and the reference lists of relevant articles. The search was up to November 30, 2015. Data extraction was performed by 2 independent investigators, and a consensus was reached with involvement of a third.

RESULTS

Ten prospective cohort studies (9 publications) were eligible in this meta-analysis. During follow-up periods ranging from 5.5 to 26 years, there were 92,647 deaths among 782,751 participants. Overall, a diet containing greater amounts of whole grains may be associated with a lower risk of all-cause, CVD-, and coronary heart disease (CHD)-specific mortality. The summary relative risks (RRs) were 0.93 (95% confidence intervals [CIs]: 0.91-0.95; Pheterogeneity < 0.001) for all-cause mortality, 0.95 (95% CIs: 0.92-0.98; Pheterogeneity < 0.001) for CVD-specific mortality, and 0.92 (95% CIs: 0.88-0.97; Pheterogeneity < 0.001) for CHD-specific mortality for an increment of 1 serving (30 g) a day of whole grain intake. The combined estimates were robust across subgroup and sensitivity analyses. Higher consumption of whole grains was not appreciably associated with risk of mortality from stroke and diabetes.

CONCLUSION

Evidence from observational cohort studies indicates inverse associations of intake of whole grains with risk of mortality from all-cause, CVD, and CHD. However, no associations with risk of deaths from stroke and diabetes were observed.

Misreport of energy intake assessed with food records and 24-h recalls compared with total energy expenditure estimated with DLW

BACKGROUND/OBJECTIVES

The accuracy of dietary assessment methods has rarely been validated using precise techniques. The objective of this work was to evaluate the validity of energy intake (EI) estimated with food records (FRs) and 24-h recalls (24hRs) against total energy expenditure (EE) estimated by the doubly labeled water (DLW) method. In addition, the magnitude of EI under-reporting was assessed along with its associated characteristics.

SUBJECTS/METHODS

The studied group included 83 adults between 20 and 60 years of age who were recruited from a population-based sample. Within-person variation-adjusted means of EI estimated from two FRs and three 24hRs were compared with EE estimated using the DLW method multiple-point protocol. The Wilcoxon signed-rank test was used to assess the differences between EI and EE, whereas Bland-Altman and survival-agreement plots assessed the agreement between the estimates.

RESULTS

The mean EE (2540 kcal) was greater than the mean reported EI for both dietary assessment methods (FR: 1774 kcal; 24hR: 1658 kcal, P<0.01). The frequency of under-reporting was lower (20%) for EI estimated with the 24hR than that estimated with the FR (32%). Men presented lower magnitude of under-reported EI than women did. For women, differences between EI and EE were lower with FR than with 24hR. Overall, FR and 24hR showed similar performance. The mean under-reported EI was ~30% for both methods.

CONCLUSIONS

Irregular meal habits, smoking and low education were associated with the under-report of EI. Both FR and 24hR are subjected to bias suggesting the need of refining the procedures applied in dietary assessment methods.

Perspective: Randomized Controlled Trials Are Not a Panacea for Diet-Related Research

Research into the role of diet in health faces a number of methodologic challenges in the choice of study design, measurement methods, and analytic options. Heavier reliance on randomized controlled trial (RCT) designs is suggested as a way to solve these challenges. We present and discuss 7 inherent and practical considerations with special relevance to RCTs designed to study diet: 1) the need for narrow focus; 2) the choice of subjects and exposures; 3) blinding of the intervention; 4) perceived asymmetry of treatment in relation to need; 5) temporal relations between dietary exposures and putative outcomes; 6) strict adherence to the intervention protocol, despite potential clinical counter-indications; and 7) the need to maintain methodologic rigor, including measuring diet carefully and frequently. Alternatives, including observational studies and adaptive intervention designs, are presented and discussed. Given high noise-to-signal ratios interjected by using inaccurate assessment methods in studies with weak or inappropriate study designs (including RCTs), it is conceivable and indeed likely that effects of diet are underestimated. No matter which designs are used, studies will require continued improvement in the assessment of dietary intake. As technology continues to improve, there is potential for enhanced accuracy and reduced user burden of dietary assessments that are applicable to a wide variety of study designs, including RCTs.

How to Build a Standardized Country-Specific Environmental Food Database for Nutritional Epidemiology Studies

There is a lack of standardized country-specific environmental data to combine with nutritional and dietary data for assessing the environmental impact of individual diets in epidemiology surveys, which are consequently reliant on environmental food datasets based on values retrieved from a heterogeneous literature. The aim of this study was to compare and assess the relative strengths and limits of a database of food greenhouse gas emissions (GHGE) values estimated with a hybrid method combining input/output and LCA approaches, with a dataset of GHGE values retrieved from the literature. France is the geographical perimeter considered in this study, but the methodology could be applied to other countries. The GHGE of 402 foodstuffs, representative of French diet, were estimated using the hybrid method. In parallel, the GHGE of individual foods were collected from existing literature. Median per-food-category GHGE values from the hybrid method and the reviewed literature were found to correlate strongly (Spearman correlation was 0.83), showing similar rankings of food categories. Median values were significantly different for only 5 (out of 29) food categories, including the ruminant meats category for which the hybrid method gave lower estimates than those from existing literature. Analysis also revealed that literature values came from heterogeneous studies that were not always sourced and that were conducted under different LCA modeling hypotheses. In contrast, the hybrid method helps build reliably-sourced, representative national standards for product-based datasets. We anticipate this hybrid method to be a starting point for better environmental impact assessments of diets.

The acceptability of repeat Internet-based hybrid diet assessment of previous 24-h dietary intake: administration of the Oxford WebQ in UK Biobank

Although dietary intake over a single 24-h period may be atypical of an individual's habitual pattern, multiple 24-h dietary assessments can be representative of habitual intake and help in assessing seasonal variation. Web-based questionnaires are convenient for the participant and result in automatic data capture for study investigators. This study reports on the acceptability of repeated web-based administration of the Oxford WebQ--a 24-h recall of frequency from a set food list suitable for self-completion from which energy and nutrient values can be automatically generated. As part of the UK Biobank study, four invitations to complete the Oxford WebQ were sent by email over a 16-month period. Overall, 176 012 (53% of those invited) participants completed the online version of the Oxford WebQ at least once and 66% completed it more than once, although only 16% completed it on all four occasions. The response rate for any one round of invitations varied between 34 and 26%. On most occasions, the Oxford WebQ was completed on the same day that they received the invitation, although this was less likely if sent on a weekend. Participants who completed the Oxford WebQ tended to be white, female, slightly older, less deprived and more educated, which is typical of health-conscious volunteer-based studies. These findings provide preliminary evidence to suggest that repeated 24-h dietary assessment via the Internet is acceptable to the public and a feasible strategy for large population-based studies.

Substitution of sugar-sweetened beverages with other beverage alternatives: a review of long-term health outcomes

BACKGROUND

Excessive consumption of sugar-sweetened beverages (SSBs) has become an intractable public health concern worldwide, making investigation of healthy beverage alternatives for SSBs imperative.

AIM

To summarize the available evidence on the effects of replacing SSBs with beverage alternatives on long-term health outcomes.

METHOD

We systematically retrieved studies from six electronic databases from inception to November 2013. Prospective cohort studies and randomized controlled trials (RCTs) examining the effects of substituting beverage alternatives for SSBs on long-term health outcomes in both children and adults were included. The quality of included studies was assessed using the Scottish Intercollegiate Guidelines Network 50 methodology checklists.

RESULTS

Six cohort studies and four RCTs were included in the systematic review with the quality rating ranging from acceptable to high. Evidence from both cohort studies and RCTs showed substitution of SSBs by various beverage alternatives was associated with long-term lower energy intake and lower weight gain. However, evidence was insufficient to draw conclusions regarding the effect of beverage substitution on other health outcomes, and which beverage alternative is the best choice.

CONCLUSIONS

Although studies on this topic are sparse, the available evidence suggests a potential beneficial effect on body weight outcomes when SSBs are replaced by water or low-calorie beverages. Further studies in this area are warranted to fully understand the long-term health implications of beverage substitutions.

Systems Epidemiology: What's in a Name?

Systems biology is an interdisciplinary effort to integrate molecular, cellular, tissue, organ, and organism levels of function into computational models that facilitate the identification of general principles. Systems medicine adds a disease focus. Systems epidemiology adds yet another level consisting of antecedents that might contribute to the disease process in populations. In etiologic and prevention research, systems-type thinking about multiple levels of causation will allow epidemiologists to identify contributors to disease at multiple levels as well as their interactions. In public health, systems epidemiology will contribute to the improvement of syndromic surveillance methods. We encourage the creation of computational simulation models that integrate information about disease etiology, pathogenetic data, and the expertise of investigators from different disciplines.

Associations between dairy intake and metabolic risk parameters in a healthy French-Canadian population

Observational studies support that dairy product intake is associated with a reduced risk of developing type 2 diabetes; however, several clinical studies report conflicting results on the association between dairy product consumption and metabolic parameters. The aim of this study was to determine associations between dairy product consumption and metabolic profile. Dietary data, using a validated food frequency questionnaire, and fasting blood samples were collected from 233 French Canadians. Plasma phospholipid (PL) fatty acids (FA) concentrations were determined by gas chromatography. Subjects consumed 2.5 ± 1.4 portions of dairy products daily, including 1.6 ± 1.3 portions of low-fat (LF) and 0.90 ± 0.70 portions of high-fat (HF) dairy products. Trans-palmitoleic acid level in plasma PL was related to HF dairy consumption (r = 0.15; p = 0.04). Total (r = –0.21; p = 0.001) and LF dairy (r = –0.20; p = 0.003) intakes were inversely correlated with fasting plasma glucose level. Total dairy intake was inversely associated to systolic blood pressure (r = –0.17; p = 0.008) and diastolic blood pressure (r = –0.14; p = 0.03). LF dairy intake was also inversely correlated with systolic blood pressure (r = –0.17; p = 0.009). Total dairy intake was correlated with plasma C-reactive protein (CRP) (r = 0.15; p = 0.03). No association was found between HF dairy consumption and the risk factors studied. In conclusion, dairy intake is inversely associated with glycaemia and blood pressure; yet, it may modify CRP levels. Moreover, trans-palmitoleic FA levels in plasma PL may be potentially used to assess full-fat dairy consumption.

Consumption of nuts and legumes and risk of stroke: a meta-analysis of prospective cohort studies

BACKGROUND AND AIM

The relationships between dietary nuts and legume intake and risk of stroke are inconsistent. We summarized the evidence by a meta-analysis of prospective cohort studies.

METHODS AND RESULTS

We systematically searched the MEDLINE and EMBASE databases up to 31 January 2014. Random-effects models were used to calculate summary relative risks (SRRs) and 95% confidence intervals (CIs). Between-study heterogeneity was assessed using the Cochran's Q and I(2) statistics. Eight prospective studies with a total of 468,887 subjects and 10,493 stroke events were included in the meta-analysis. Overall, a diet containing greater amounts of legumes may be not associated with a lower risk of stroke (SRR = 0.95, 95% CI: 0.84-1.08; P(heterogeneity) = 0.091, I(2) = 43.2%); however, a diet containing greater amounts of nuts may be associated with a lower risk of stroke (SRR = 0.90, 95% CI: 0.81-0.99; P(heterogeneity) = 0.527, I(2) = 0). Gender significantly modified the effects of nut consumption on stroke risk, and high nut intake was associated with reduced risk of stroke in women (SRR = 0.85, 95% CI: 0.75-0.97) other than in men (SRR = 0.95, 95% CI: 0.82-1.11).

CONCLUSION

The current meta-analysis provides some evidences for the hypothesis that high intake of dietary nut was inversely associated with stroke risk, whereas dietary legumes intake was not associated with stroke risk.

Validation of a pre-coded food diary used among 60-80 year old men: comparison of self-reported energy intake with objectively recorded energy expenditure

Objective

To validate energy intake (EI) estimated from a pre-coded food diary (PFD) against energy expenditure (EE) measured with a valid physical activity monitor (SenseWear Pro₃ Armband) and to evaluate whether misreporting was associated with overweight/obesity in a group of elderly men.

Methods

Forty-seven healthy Norwegian men, 60–80 years old, completed the study. As this study was part of a larger intervention study, cross-sectional data were collected at both baseline and post-test. Participants recorded their food intake for four consecutive days using food diaries and wore SenseWear Pro₃ Armband (SWA) during the same period. Only participants with complete data sets at both baseline and post-test were included in the study.

Results

The group average EI was 17% lower at baseline and 18% lower at post-test compared to measured EE. Mean difference from Bland-Altman plot for EI and EE was −1.5 MJ/day (±1.96 SD: −7.0, 4.0 MJ/day) at baseline and −1.6 MJ/day (−6.6, 3.4 MJ/day) at post-test. The intraclass correlation coefficient (ICC) was 0.30 (95% CI: 0.02, 0.54, p = 0.018) at baseline and 0.34 (0.06, 0.57, p = 0.009) at post-test. Higher values of underreporting was shown among overweight/obese compared to normal weight participants at both baseline and post-test (p≤ 0.001), respectively.

Conclusions

The results indicate that the PFD could be a useful tool for estimating energy intake in normal weight elderly men. On the other hand, the PFD seems to be less suitable for estimating energy intake in overweight/obese elderly men.

The Dutch Healthy Diet index as assessed by 24 h recalls and FFQ: associations with biomarkers from a cross-sectional study

The Dutch Healthy Diet index (DHD-index) was developed using data from two 24 h recalls (24hR) and appeared useful to evaluate diet quality in Dutch adults. As many epidemiologic studies use FFQ, we now estimated the DHD-index score using FFQ data. We compared whether this score showed similar associations with participants' characteristics, micronutrient intakes, and biomarkers of intake and metabolism compared with the DHD-index using 24hR data. Data of 121 Dutch participants of the European Food Consumption Validation study were used. Dietary intake was assessed by two 24hR and a 180-item FFQ. Biomarkers measured were serum total cholesterol and carotenoids, EPA + DHA in plasma phospholipids and 24 h urinary Na. A correlation of 0·48 (95 % CI 0·33, 0·61) was observed between the DHD-index score based on 24hR data and on FFQ data. Classification of participants into the same tertiles of the DHD-index was achieved for 57 %. Women showed higher DHD-index scores. Energy intake was inversely associated with both DHD-index scores. Furthermore, age and intakes of folate, Fe, Mg, K, vitamin B6 and vitamin C were positively associated with both DHD-index scores. DHD-index scores showed acceptable correlations with the four combined biomarkers taking energy intake into account (r 24hR 0.55; r FFQ 0.51). In conclusion, the DHD-index score based on FFQ data shows similar associations with participants' characteristics, energy intake, micronutrient intake and biomarkers compared with the score based on 24hR data. Furthermore, ranking of participants was acceptable for both methods. FFQ data may therefore be used to assess diet quality using the DHD-index in Dutch populations.