Mediation analyses: applications in nutrition research and reading the literature

Diet quality partially mediates the association between ultraprocessed food consumption and adiposity indicators

OBJECTIVE

This study evaluated the potential role of overall diet quality in the associations between ultraprocessed food (UPF) consumption and adiposity indicators among Korean adults.

METHODS

Baseline data of participants (n = 4331) of the Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) cohort study were obtained. Dietary information was collected by a validated food frequency questionnaire. UPF was defined using the NOVA classification. Overall diet quality was assessed using the Korean Healthy Eating Index. Adiposity indicators included BMI, waist circumference, percentage body fat by bioimpedance, and visceral fat mass by whole-body dual-energy x-ray absorptiometry. Mediation analysis after adjustment for potential confounders was performed.

RESULTS

UPF intake was associated with higher adiposity indicators after adjustment for confounders. The mediating effect of the Korean Healthy Eating Index on the relationship between UPF consumption and each adiposity indicator was 35.6% (95% CI: 4.9% to 255.9%) for BMI, 38.3% (17.9% to 132.1%) for waist circumference, 40.2% (8.3% to 259.4%) for percentage body fat, and 60.7% (-396.4% to 662.7%) for visceral fat mass.

CONCLUSIONS

UPF consumption was positively associated with adiposity indicators, which were partially attributed to the overall diet quality. Further studies are needed to better understand the causal mechanisms of these associations.

Do markers of adiposity and glycaemia mediate the association between low carbohydrate diet and cardiovascular risk factors: findings from the UK National Diet and Nutrition Survey (NDNS) 2008-2016

Objectives

To examine the associations between low carbohydrate diet (LCD) and conventional cardiovascular risk factors and investigate whether these associations are mediated by body mass index (BMI), waist circumference (WC) and haemoglobin A1c (HbA1c) applying causal mediation analyses.

Methods

We included 3640 adults aged 45-80 years from the UK National Diet and Nutrition Survey programme (2008-2016) with data on dietary intake, anthropometric and biochemical parameters. Four hypothetical interventions were examined: (1) LCD, (2) Low carbohydrate (LC) and high fibre diet (LCHF), (3) LC and high saturated fat diet (LCHS) and (4) LC and high unsaturated fat diet (LCHU). BMI and WC were used as markers of obesity. Biochemical markers included HbA1c, total cholesterol, high-density lipoprotein and low-density lipoprotein (LDL) cholesterol, triglycerides, systolic and diastolic blood pressure and C reactive protein (CRP). BMI, WC and HbA1c were used as a mediator of the effects. The analysis was adjusted for sociodemographic characteristic, smoking, estimated total energy intake, alcohol consumption and antihypertensive medication. To identify a potential causal effect of LCD on cardiovascular disease (CVD) risk, we estimated the average treatment effect, and corresponding p values and CI for the total, indirect and direct effect of the treatment on the outcome.

Results

BMI, WC and HbA1c fully mediated the association between LCD and triglycerides and fully mediated the effects of LCHF on LDL, although BMI and WC were not sufficient to fully mediate the effects of LCHF on triglycerides and CRP. BMI alone fully mediated the effects of LCHS on HbA1c, triglycerides, LDL and CRP. None of these mediators explained the effect of LCHU on CVD risk markers.

Conclusion

The causal hypotheses tested in this study demonstrate that individuals on LCD with high fibre intakes improved their CVD markers as expected, but those on LCD who increase fat intake had no effects on CVD markers mediated by obesity and diabetes.

Mediation Analysis in Manual Therapy Research

Objective

The purpose of this study was to illustrate the applicability of mediation analysis in the manual therapy field by assessing whether pain intensity, duration of pain, or the change in systolic blood pressure mediated the heart rate variability (HRV) of patients with musculoskeletal pain who received manual therapy.

Methods

A secondary data analysis from a 3-arm, parallel, randomized, placebo-controlled, assessor-blinded, superiority trial was performed. Participants were randomized into spinal manipulation, myofascial manipulation, or placebo groups. Cardiovascular autonomic control was inferred from resting HRV variables (low-high frequency power ratio; LF/HF) and blood pressure responsiveness to a sympathoexcitatory stimulus (cold pressor test). Pain intensity and duration were assessed. Mediation models analyzed whether pain intensity, duration, or blood pressure independently affected the improvement of the cardiovascular autonomic control of patients with musculoskeletal pain after intervention.

Results

The first assumption of mediation was met for LF/HF with statistical evidence of a total effect of spinal manipulation, as compared with placebo on HRV outcomes (β = 0.77 [0.17-1.30]); second and third assumptions showed no statistical evidence of a relationship between the intervention and pain intensity (β = -5.30 [-39.48 to 28.87]), pain intensity, and LF/HF (β = 0.00 [-0.01 to 0.01]).

Conclusion

In this study of causal mediation analysis, the baseline pain intensity, duration of pain, and responsiveness of the systolic blood pressure to a sympathoexcitatory stimulus did not mediate the effects of the spinal manipulation on the cardiovascular autonomic control of patients with musculoskeletal pain. Accordingly, the immediate effect of spinal manipulation on the cardiac vagal modulation of patients with musculoskeletal pain may more likely be related to the intervention rather than the mediators investigated.

Triglycerides and systolic blood pressure negatively mediate the direct relationship of vitamin D status to resting energy expenditure: A cross sectional analysis

BACKGROUND AND AIMS

We determined whether individual components of metabolic syndrome (MetS) mediated the direct association of vitamin D status (25OHD) on resting energy expenditure (REE).

METHODS

Multiple linear regression determined predictors of REE from data on 180 men and women from two ethnic groups. We then modelled a mediation pathway through components of MetS on the direct association between 25OHD and REE. The mediation modelling used the PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with the adjustment for different sets of covariates.

RESULTS

REE was significantly predicted by age, fat mass (FM), fat free mass (FFM), ethnicity, inverse ln insulin, 25OHD, triglycerides (TG), systolic blood pressure (SBP) and, to some extent, by time of REE measurements (p < 0.094). Adjustment for all these covariates, resulted in a negative indirect mediation effect of TG [β coefficient (bootstrapped SE): 0.95 (0.519); bootstrapped 95% CI: 2.172, -0.165; p < 0.05] and a concurrent negative mediation of SBP [β coefficient (bootstrapped SE): 0.72(0.484); bootstrapped 95% CI: 1.851, -0.011; p < 0.05]. There remained a positive direct pathway from 25OHD to REE [β coefficient (S.E): 4.715 (2.129); p = 0.028], however the total effect of 25OHD was dampened [β coefficient (S.E): 3.04 (2.126); p = 0.154].

CONCLUSIONS

Independent of insulin sensitivity, a negative mediation by TG and SBP dampened the overall effect of 25OHD on REE.

Investigating the moderators and mediators of an effective sleep intervention in the Prevention of Overweight in Infancy (POI) randomized controlled trial: Exploratory analyses

The Prevention of Overweight in Infancy (POI) sleep intervention halved obesity risk at 2 years of age. However, the intervention mechanisms are unclear. Consequently, the objective of the current work was to use exploratory analyses to investigate potential moderators and mediators of the sleep intervention on obesity outcomes at age 2 years. Data were collected between 2009 and 2012. The effect of demographic and study design variables on body mass index z-score (BMI z-score) and obesity was compared in moderator subgroups at 2 years of age (n = 683, 85%). Mediating effects of child and parent-household variables assessed whether the sleep intervention resulted in meaningful changes in the mediating variable (defined as changes which were statistically significant [p < .05] or where the effect size was ≥0.15 SD), followed by assessing relationships with obesity outcomes. The sleep intervention appeared most effective in children in higher deprivation areas (effect on BMI z-score -0.25 [-0.53, 0.04], effect on obesity odds ratio [OR] 0.43 [0.16, 1.13]), and with mothers of non-European, non-Māori ethnicity (effect on BMI z-score -0.27 [-0.73, 0.20], effect on obesity OR 0.13 [95% confidence interval 0.01, 1.11]). This suggested moderation by deprivation and ethnicity. Aspects of sleep improved meaningfully in children after intervention but did not significantly relate to obesity outcomes, and other outcomes were not meaningfully affected by the sleep intervention. Thus, mediation was not indicated. Overall, the POI sleep intervention improved obesity outcomes at 2 years, and the current work identified some potential moderators, but no mediators.

Examination of Associations between Physical Activity and Eating Identities among College-aged Adults Living in Hawai'i

While physical activity and diet behaviors are correlated, mechanisms underlying associations have rarely been examined. This study examined associations between physical activity identity and eating identity among college-aged adults in Hawai'i to provide guidance for future multiple behavior change interventions. This study was a cross-sectional analysis of data collected between September 2013 and January 2014. Participants were 40 college students attending 4-year and 2-year institutions within the University of Hawai'i system. Total physical activity identity score and dimensions were measured using the Athlete Identity Questionnaire. Eating identity subtypes were measured using the Eating Identity Type Inventory. Associations between physical activity identity total score, 4 physical activity identity dimensions (appearance, importance, competence, and encouragement), and 4 eating identity subtypes (healthy, emotional, meat, and picky) were examined using multiple linear regressions. A significant positive association was found between total physical activity identity score and the healthy eating subtype and a negative association with the picky eating subtype. The physical activity dimension importance had a significant positive association with the healthy eating subtype, appearance a negative association with the emotional eating subtype, and competence a positive association with the meat eating subtype but a negative association with the picky eating subtype. The findings suggest important overlap in identities for physical activity and diet. Measurement of physical activity identity and eating identity as well as tailored intervention strategies should be incorporated into more behavior change research.

Hypothesized pathways for the association of vitamin D status and insulin sensitivity with resting energy expenditure: a cross sectional mediation analysis in Australian adults of European ancestry

Background

The role of vitamin D in human energy expenditure requires confirmation. We explored whether insulin sensitivity (IS)/insulin resistance (IR) mediated the association of vitamin D status (25OHD) on resting energy expenditure (REE).

Methods

REE, body composition (by DEXA) and clinical biochemistry of 155 Australian men and women were collated. A hypothesized mediation pathway through IS/IR on the direct association between 25OHD and REE was modeled, using three surrogate indices of IS/IR: McAuley’s insulin sensitivity index (McA), Quantitative insulin sensitivity check index (QUICKI) and triglyceride to glucose ratio (TYG). The modeling was performed on PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with and without the adjustment for covariates.

Results

Unadjusted models indicated a sizeable negative mediation by all IS/IR indices but no significant direct effect of 25OHD on REE. On adjustment for covariates, a negative indirect mediation effect of McA [β coefficient (SE) −2.1(0.821); bootstrapped 95% CI:−3.934, −0.703; p < 0.05] and a similar negative mediation of TYG [−1.935 (0.780); bootstrapped 95% CI: (−3.679, −0.622; p < 0.05] was observed. These models also showed a positive direct effect of 25OHD on REE. In contrast, QUICKI made a smaller contribution to the total effect though in the same direction as the other two measures [−0.783 (0.534); bootstrapped 95% CI: (−1.939, 0.134; P > 0.05].

Conclusions

A sizeable, partial, negative mediation of IS/IR on the direct relationship between 25OHD and REE, dampened the total effect of vitamin D on REE. Validation of the proposed causal framework would clarify vitamin D’s role in human energy metabolism.

The Role of Diet Quality in Mediating the Association between Ultra-Processed Food Intake, Obesity and Health-Related Outcomes: A Review of Prospective Cohort Studies

Prospective cohort studies show that higher intakes of ultra-processed food (UPF) increase the risk of obesity and obesity-related outcomes, including cardiovascular disease, cancer and type 2 diabetes. Whether ultra-processing itself is detrimental, or whether UPFs just have a lower nutritional quality, is debated. Higher UPF intakes are inversely associated with fruit, vegetables, legumes and seafood consumption. Therefore, the association between UPFs and poor health could simply be from excess nutrient intake or from a less healthful dietary pattern. If so, adjustment for dietary quality or pattern should explain or greatly reduce the size of the significant associations between UPFs and health-related outcomes. Here, we provide an overview of the literature and by using a novel approach, review the relative impact of adjusting for diet quality/patterns on the reported associations between UPF intake and health-related outcomes in prospective cohort studies. We find that the majority of the associations between UPFs, obesity and health-related outcomes remain significant and unchanged in magnitude after adjustment for diet quality or pattern. Our findings suggest that the adverse consequences of UPFs are independent of dietary quality or pattern, questioning the utility of reformulation to mitigate against the obesity pandemic and wider negative health outcomes of UPFs.

TV advertising and dietary intake in adolescents: a pre- and post- study of Chile's Food Marketing Policy

Background

The first phase of a comprehensive marketing policy was implemented in Chile in 2016. The policy restricted child-directed marketing of foods and beverages considered high in energy, total sugars, sodium or saturated fat (“high-in”). The objective of this study was to examine the role of high-in TV food advertising as a mediator in the association between policy implementation and consumption of high-in foods and beverages between 2016 and 2017.

Methods

Dietary data were from 24-hour diet recalls collected in 2016 and 2017 in a cohort of 12–14 y children (n = 721). Television use was assessed concurrently and linked to analyses of food advertisements on broadcast and paid television to derive individual-level estimates of exposure to high-in food advertising. A multilevel mediation analysis examined direct and indirect effects of the policy through advertising exposure.

Results

Following the policy implementation, high-in advertising exposure was significantly reduced (p < 0.01). High-in food intake decreased in adolescents with lower levels, but not higher levels, of high-in advertising at baseline. We did not find evidence of mediation by changes in high-in ad exposure.

Conclusions

Adolescents’ exposure to high-in TV advertising decreased after the 2016 implementation of the Chilean Food Labeling and Marketing Law. However, evidence that changes in advertisement mediated dietary changes was not found. Further research is needed to understand how marketing changes will relate to dietary changes after full implementation of the law and in the long term.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12966-021-01126-7.

Behavioural mediators of reduced energy intake in a physical activity, diet, and sleep behaviour weight loss intervention in adults

Reduced energy intake is a major driver of weight loss and evidence suggests that physical activity, dietary, and sleep behaviours interact to influence energy intake. Energy restriction can be challenging to sustain. Therefore to improve intervention efficacy, evaluation of how changes in physical activity, diet, and sleep behaviours mediate reduced energy intake in adults with overweight/obesity who participated in a six-month multiple-behaviour-change weight loss intervention was undertaken. This was a secondary analysis of a 3-arm randomised controlled trial. Adults with body mass index (BMI) 25-40 kg/m² were randomised to either: a physical activity and diet intervention; physical activity, diet, and sleep intervention; or wait-list control. Physical activity, dietary intake, and sleep was measured at baseline and six-months using validated measures. The two intervention groups were pooled and compared to the control. Structural equation modelling was used to estimate the mediated effects (AB Coefficient) of the intervention on total energy intake. One hundred and sixteen adults (70% female, 44.5y, BMI 31.7 kg/m²) were enrolled and 70% (n = 81) completed the six-month assessment. The significant intervention effect on energy intake at six-months (-1011 kJ/day, 95% CI -1922, -101) was partially mediated by reduced fat intake (AB = -761.12, 95% CI -1564.25, -53.74) and reduced consumption of energy-dense, nutrient-poor foods (AB = -576.19, 95% CI -1189.23, -97.26). In this study, reducing fat intake and consumption of energy-dense, nutrient-poor foods was an effective strategy for reducing daily energy intake in adults with overweight/obesity at six-months. These strategies should be explicitly targeted in future weight loss interventions.

Examining Chile's unique food marketing policy: TV advertising and dietary intake in preschool children, a pre- and post- policy study

BACKGROUND

The Chilean government implemented the first phase of a comprehensive marketing policy in 2016, restricting child-directed marketing of products high in energy, total sugars, sodium or saturated fat (hereafter "high-in").

OBJECTIVES

To examine the role that high-in TV food advertising had in the effect of the policy on consumption of high-in products between 2016 and 2017.

METHODS

Dietary data were obtained from 24-hour diet recall measured in 2016 (n = 940) and 2017 (n = 853), pre- and post-policy, from a cohort of 4 to 6 years children. Television use was linked to analyses of food advertisements to derive individual-level estimates of exposure to advertising. A multilevel mediation analysis examined direct and indirect effects of the policy through advertising exposure.

RESULTS

Children's high-in food consumption and advertising exposure declined significantly from 2016 to 2017 (P < .01). Consumption changes were not significantly mediated by changes in advertising exposure, which might suggest other elements of the Chilean Law potentially driving decreases in consumption to a greater extent than TV ads.

CONCLUSIONS

Preschoolers' exposure to high-in advertising and consumption of high-in products decreased post-policy. Further research is needed to understand how marketing changes will relate to dietary changes after full implementation of the law and in the long term.

Functional decline in geriatric rehabilitation ward; is it ascribable to hospital acquired infection? A prospective cohort study

BACKGROUND

In some European countries, including France, older patients with functional decline in acute units are transferred to geriatric rehabilitation units. Some patients may not benefit from their stay in a geriatric rehabilitation unit and paradoxically worsened their functional status. Previous prognostic models of functional decline are based on only baseline parameters. However, some events can occur during rehabilitation and modify the association between baseline parameters and rehabilitation performance such as heart failure episode, falls or hospital-acquired infection (HAI). The incidence of functional decline in these units and factors associated with this decline have not been clearly identified.

METHODS

We used a prospective cohort of consecutive patients aged ≥75 years admitted to a geriatric rehabilitation unit in a French university hospital. The main endpoint was functional decline defined by at least an one-point decrease in Activities of Daily Living (ADL) score during the stay. Baseline social and geriatric characteristics were recorded and comorbidities were sought by the Cumulative Illness Rating Scale for Geriatrics (CIRS-G). During follow-up, hospital-acquired infection (HAI) was recorded, as was ADL score at discharge. Multivariate logistic regression and mediation analyses were used to identify factors associated with ADL decrease.

RESULTS

Among the 252 eligible patients, 160 (median age 84 years [interquartile range (IQR) 80-88] had available ADL scores at baseline (median score 7 [IQR 4-10]) and at discharge (median 9 [6-12]). Median CIRS-G score was 11 [8-13], 23 (14%) had a pulmonary HAI; 28 (17.5%) showed functional decline. On multivariable analysis, functional decline was associated with comorbidities (global CIRS-G score, P = 0.02, CIRS-G for respiratory disease [CIRS-G-R] ≥2, P = 0.02, or psychiatric disease, P = 0.02) and albumin level < 35 g/l (p = 0.03). Significant associations were found between functional decline and CIRS-G-R (OR 3.07 [95%CI 1.27-7.41], p = 0.01), between functional decline and pulmonary HAI (OR 3.12 [1.17-8.32],p = 0.02), and between CIRS-G-R and pulmonary HAI (OR 12.9[4.4-37.7], p = 0.0001). Theses associations and the reduced effect of CIRS-G-R on functional decline after adjusting for pulmonary HAI (OR 2.26 [0.83-6.16], p = 0.11) suggested partial mediation of pulmonary HAI in the relation between CIRS-G-R and functional decline.

CONCLUSION

Baseline comorbidities were independently associated with functional decline in patients hospitalized in a geriatric rehabilitation unit. Pulmonary HAI may have mediated this association. We need to better identify patients at risk of functional decline before transfer to a rehabilitation unit and to test the implementation of modern and individual programs of rehabilitation outside the hospital for these patients.

Influence of pre-schooler and parent nutrition education on carotenoid levels of Mexican-heritage children

OBJECTIVE

To determine the mediating effect of direct preschool and parent nutrition education on changes in skin carotenoids scores over 2 years in children of Mexican heritage.

DESIGN

In a quasi-experimental, community-based study, two school districts were randomly assigned to either a comparison group (parent workshops unrelated to nutrition) or a childhood obesity prevention intervention group which included nutrition education at family nights for parents and at school for children. Changes in skin carotenoid intensity scores (diffCAROT, year 2015 minus 2013) were measured in children as a proxy for fruit and vegetable consumption using Resonance Raman Spectroscopy.

SETTING

Two rural, low-income, school districts from a county in California's Central Valley.

PARTICIPANTS

316 Mexican heritage families with children aged 3-8 years.

RESULTS

Intervention group children improved over 2 years in skin carotenoid scores relative to comparison group children (diffCAROT mean +1419 (sd 9540) v. -3473 (sd 9272), P = 0·0001). Parent attendance at nutrition education classes partially mediated the intervention effect on diffCAROT (P = 0·02). Controlling for child's age and other covariates, participation in preschool during the study had a significant positive effect on diffCAROT among intervention children compared with controls (P < 0·03), whereas no significant difference by group was observed among those not enrolled in preschool or already enrolled in elementary school.

CONCLUSIONS

Programmes that combine direct parent and preschool nutrition education may be effective in low-income Mexican heritage families to improve children's intake of fruit and vegetables.

Obesity, Insulin Resistance, and Hyperandrogenism Mediate the Link between Poor Diet Quality and Ovarian Dysmorphology in Reproductive-Aged Women

The relationship between diet quality and ovarian morphology has biological plausibility yet remains unclear and was therefore evaluated. In a multicenter cross-sectional analysis, four dietary patterns were scored for 111 consecutive reproductive-aged women (18-45 years) using (1) Healthy Eating Index (HEI-2015); (2) alternative HEI-2010; (3) alternate Mediterranean Diet (aMED); (4) and Dietary Approaches to Stop Hypertension (DASH) indices. Ovarian volume (OV) and follicle number per ovary (FNPO) were evaluated on transvaginal ultrasonography. Relationships between dietary and ovarian morphology indices were evaluated by linear regression and mediation analyses. Associations between aMED and DASH scores and OV/FNPO were completely mediated by obesity, insulin resistance, and hyperandrogenism (All: p < 0.05), unlike direct associations (All: p ≥ 0.89). Namely, a 1-standard deviation [SD] increase in aMED score was associated with decreases in OV (0.09 SD; 0.4 mL) through reducing waist circumference. Likewise, a 1 SD increase in aMED and DASH score was associated with decreases in OV (0.07 SD; 0.3 mL) by reducing glucose response to a 75 g glucose tolerance test. A 1 SD increase in DASH score was associated with decreased FNPO (0.07 SD; 2 follicles) by reducing free androgen index (All: p < 0.05). Adherence to aMED and DASH eating plans was indirectly associated with significant improvements in ovarian form, providing novel mechanistic insights for future interventions about contributions of diet quality on ovarian function.

Food-related behaviours among individuals with overweight/obesity and normal body weight

BACKGROUND

Emotional eating is a factor associated with a negative body image and other problematic eating behaviours. In this context little is known about differences between individuals with overweight and obesity and those with normal body weight. The main aim of the study was to evaluate the role of emotional eating in the relationship between the desire to consume chocolate and the wish to avoid social situations related to food and body exposures. For this purpose, we tested the direct, indirect and buffer effects. In addition, we used moderated mediation by introducing snacking into the model.

METHODS

The study included 123 outpatients with excessive body weight and 123 individuals with normal weight. The mean of body mass index (BMI) in the first group was 30.19 kg/m2 (SD = 4.37) and, in the second, it was 23.02 kg/m2 (SD = 1.20). The Three-Factor Eating Questionnaire, the Attitudes to Chocolate Questionnaire and the Body Image Avoidance Questionnaire were used.

RESULTS

Results show that in all individuals, the greater emotional eating is, the greater the desire for chocolate consumption and avoidance of social situations related to food and body exposures are. In addition, the desire for chocolate consumption are positively associated with avoidance of social situations related to food and body exposures in both group. Among individuals with excessive and normal body weight, emotional eating is a significant mediator in the relationship between desire for chocolate consumption and avoidance of social situations related to food and body exposures. However, it does not moderate the relationship between these variables. Outcomes show that there is a significant model of moderated mediation of the link between social situation-avoidance related to food and body exposure and the desire to consume chocolate through emotional eating, moderated by snacking among individuals with normal body weight. A similar effect has not been discovered in the group with excessive body weight.

CONCLUSION

The presented results show that among people with varied BMI categories, emotional eating is connected to craving chocolate and avoidance of social situations related to food and body exposure that plays only the role of mediation. In addition, snacking is crucial for this relationship among the group with normal body weight.

Dietary manganese and type 2 diabetes mellitus: two prospective cohort studies in China

AIMS/HYPOTHESIS

The association between dietary Mn and type 2 diabetes is unclear. We aimed to elucidate whether dietary Mn is associated with type 2 diabetes, to investigate whether this association is independent of dietary total antioxidant capacity (TAC) and to explore the underlying mechanisms in their association.

METHODS

Two prospective cohorts of 3350 and 7133 Chinese adults (20-74 years old) were enrolled including, respectively, 244 and 578 individuals newly diagnosed with type 2 diabetes, with mean values of 4.2 and 5.3 years of follow-up. Cox's proportional-hazards regression and linear regression were performed to investigate the association between dietary Mn and type 2 diabetes (diagnosed by OGTT) or HbA_lc and to analyse the joint association between dietary Mn and TAC. Restricted cubic spline (RCS) regression was applied to the non-linear association between dietary Mn and incidence of type 2 diabetes. Mediation analysis was applied to explore potential mediators in their association in a subgroup of 500 participants.

RESULTS

Dietary Mn intakes were 4.58 ± 1.04 and 4.61 ± 1.08 (mean ± SD) mg/day in the two cohorts. Dietary Mn was inversely associated with type 2 diabetes incidence and HbA_lc concentration in both cohorts (p_trend < 0.01 and <0.01 for type 2 diabetes, and p_trend < 0.01 and =0.02 for HbA_lc, respectively, in each cohort) independent of TAC, adjusted for age, sex, BMI, tobacco use, alcohol consumption, physical activity, diabetes inheritance, total energy, carbohydrate, total fatty acids, fibre, calcium, Mg, hypertension, hyperlipidaemia, and impaired glucose tolerance or FBG (all at baseline). Their inverse association was stronger in the presence of diets with high, compared with low, TAC. In RCS, intakes of >6.01 and 6.10-6.97 mg/day were associated with a significantly lower type 2 diabetes incidence in the two respective cohorts. Mediation analysis showed that high plasma Mn and low oxidative stress (increased Mn superoxide dismutase and decreased 8-hydroxydeoxyguanosine) contributed to the association between dietary Mn and both type 2 diabetes and HbA_lc.

CONCLUSIONS/INTERPRETATION

Dietary Mn was inversely associated with type 2 diabetes independently of TAC. In addition, this association was stronger in a high- rather than low-TAC diet. Plasma Mn and oxidative stress were mediators in the association between dietary Mn and type 2 diabetes. Future studies on absolute Mn intake should be conducted to study the potential non-linearity and optimal levels of dietary Mn and type 2 diabetes.

Mediation Analysis as a Means of Identifying Dietary Components That Differentially Affect the Fecal Microbiota of Infants Weaned by Modified Baby-Led and Traditional Approaches

The introduction of "solids" (i.e., complementary foods) to the milk-only diet in early infancy affects the development of the gut microbiota. The aim of this study was to determine whether a "baby-led" approach to complementary feeding that encourages the early introduction of an adult-type diet results in alterations of the gut microbiota composition compared to traditional spoon-feeding. The Baby-Led Introduction to SolidS (BLISS) study randomized 206 infants to BLISS (a modified version of baby-led weaning [BLW], the introduction of solids at 6 months of age, followed by self-feeding of family foods) or control (traditional spoon-feeding of purées) groups. Fecal microbiotas and 3-day weighed-diet records were analyzed for a subset of 74 infants at 7 and 12 months of age. The composition of the microbiota was determined by sequencing of 16S rRNA genes amplified by PCR from bulk DNA extracted from feces. Diet records were used to estimate food and dietary fiber intake. Alpha diversity (number of operational taxonomic units [OTUs]) was significantly lower in BLISS infants at 12 months of age (difference [95% confidence interval {CI}] of 31 OTUs [3.4 to 58.5]; P = 0.028), and while there were no significant differences between control and BLISS infants in relative abundances of Bifidobacteriaceae, Enterobacteriaceae, Veillonellaceae, Bacteroidaceae, Erysipelotrichaceae, Lachnospiraceae, or Ruminococcaceae at 7 or 12 months of age, OTUs representing the genus Roseburia were less prevalent in BLISS microbiotas at 12 months. Mediation models demonstrated that the intake of "fruit and vegetables" and "dietary fiber" explained 29% and 25%, respectively, of the relationship between group (BLISS versus control) and alpha diversity.IMPORTANCE The introduction of solid foods (complementary feeding or weaning) to infants leads to more-complex compositions of microbial communities (microbiota or microbiome) in the gut. In baby-led weaning (BLW), infants are given only finger foods that they can pick up and feed themselves-there is no parental spoon-feeding of puréed baby foods-and infants are encouraged to eat family meals. BLW is a new approach to infant feeding that is increasing in popularity in the United States, New Zealand, the United Kingdom, and Canada. We used mediation modeling, commonly used in health research but not in microbiota studies until now, to identify particular dietary components that affected the development of the infant gut microbiota.

Incorporating positive youth development into the therapeutic model for incarcerated young woman

Young women in the juvenile justice system have high rates of prior physical and sexual abuse, substance use and psychiatric disorders. Understandably services usually are based on a therapeutic model to address those needs. Positive Youth Development (PYD) is a complementary alternative format that aims to provide resilience, life competencies, and self efficacy for pro-social actions. We provide a narrative review of PYD programs with a focus on how those relate to youth in closed custody. Sleep and physical activity are two behaviors where incarcerated young women still have personal agency, and we present the additional relevance of those program aspects. We describe methods and findings from a feasibility trial of an existing evidence-based, peer-led program for young women high school athletes used with incarcerated young women. Findings are placed in the context of established models of behavior change. The program was feasible and acceptable, and in this small trial, results demonstrate the format's potential efficacy. PYD may provide a trajectory of success and assets that could durably assist these young women following incarceration.

A Mediation Analysis of Mothers' Dietary Intake: The Entre Familia: Reflejos de Salud Randomized Controlled Trial

AIMS

Examine intervention effects among mothers involved in a healthy eating randomized controlled trial. Furthermore, examine the mediating roles of individual and familial influences on observed outcomes.

METHODS

Between 2009 and 2011, 361 families were recruited; half were assigned to an 11-session community health worker-delivered family-based intervention targeting Spanish-speaking Latino families in Imperial County, California. The intervention was delivered over a 4-month period. Home visits and telephone calls were delivered approximately weekly, with tapering near the end of the intervention to promote independence from the promotora. In this article, mothers' self-reported dietary intake was the primary outcome. Evaluation measures were taken at baseline, 4 months, and 10 months.

RESULTS

Daily servings of fruits were higher among intervention versus control mothers (mean = 1.86 vs. mean = 1.47; effect size [ES] = 0.22) at 10 months post-baseline. Mothers in the intervention versus control condition also reported consuming a lower percent energy from fat (mean = 30.0% vs. 31.0%; ES = 0.30) and a higher diet quality (mean = 2.93 vs. mean = 2.67; ES = 0.29). Mediators of improvements were behavioral strategies to increase fiber and lower fat intake, family support for vegetable purchasing, and decreased unhealthy eating behaviors and perceived family barriers to healthy eating.

DISCUSSION AND CONCLUSION

Family-based behavioral interventions are effective for changing the skills and family system needed to improve diet among Latina mothers. Health care providers and other practitioners are encouraged to target skill development and fostering a socially supportive environment.

Interrelationship between food security status, home availability of variety of fruits and vegetables and their dietary intake among low-income pregnant women

OBJECTIVE

To (i) determine differences in the availability of variety of fruits and vegetables (F&V) at home by food security status; and (ii) examine the inter-associations between food security status, availability of variety of F&V at home and frequency of F&V intake, among low-income pregnant women. Design/Setting Participants were interviewed to collect food security status, home availability of variety of F&V and frequency of F&V intake. Bivariate analyses, multivariate regression and exploratory mediation analyses were conducted using IBM SPSS Statistics version 23.0 and the PROCESS macro.

SUBJECTS

Low-income pregnant women (n 198) were interviewed if they were ≥18 years of age, in the second trimester of pregnancy, and spoke English or Spanish.

RESULTS

Low/very low food security was found among 43 % of participants. Compared with fully food-secure participants, very low food-secure participants reported a lower variety of fruits (P=0·028) and vegetables (P=0·058) available at home. Mediation analyses indicated that through home availability of variety of fresh F&V, food security status was associated with the daily intake of F&V (indirect effect (95 % CI): fresh fruits, -0·039 (-0·074, -0·013); fresh vegetables, -0·048 (-0·083, -0·023)). As food security worsened, the available variety of fresh F&V decreased, which was associated with lower intake.

CONCLUSIONS

The study highlights the interlink between food security, home food environment and diet quality, and the importance of nutrition education intervention to promote a healthy home food environment and improved pregnancy outcomes among low-income women.

Empiric validation of a process for behavior change

Most behavior change trials focus on outcomes rather than deconstructing how those outcomes related to programmatic theoretical underpinnings and intervention components. In this report, the process of change is compared for three evidence-based programs' that shared theories, intervention elements and potential mediating variables. Each investigation was a randomized trial that assessed pre- and post- intervention variables using survey constructs with established reliability. Each also used mediation analyses to define relationships. The findings were combined using a pattern matching approach. Surprisingly, knowledge was a significant mediator in each program (a and b path effects [p<0.01]). Norms, perceived control abilities, and self-monitoring were confirmed in at least two studies (p<0.01 for each). Replication of findings across studies with a common design but varied populations provides a robust validation of the theory and processes of an effective intervention. Combined findings also demonstrate a means to substantiate process aspects and theoretical models to advance understanding of behavior change.

Best (but oft-forgotten) practices: mediation analysis

This contribution in the "Best (but Oft-Forgotten) Practices" series considers mediation analysis. A mediator (sometimes referred to as an intermediate variable, surrogate endpoint, or intermediate endpoint) is a third variable that explains how or why ≥2 other variables relate in a putative causal pathway. The current article discusses mediation analysis with the ultimate intention of helping nutrition researchers to clarify the rationale for examining mediation, avoid common pitfalls when using the model, and conduct well-informed analyses that can contribute to improving causal inference in evaluations of underlying mechanisms of effects on nutrition-related behavioral and health outcomes. We give specific attention to underevaluated limitations inherent in common approaches to mediation. In addition, we discuss how to conduct a power analysis for mediation models and offer an applied example to demonstrate mediation analysis. Finally, we provide an example write-up of mediation analysis results as a model for applied researchers.

Increased cytokine production by monocytes from human subjects who consumed grape powder was not mediated by differences in dietary intake patterns

Recently, in a randomized, double-blind crossover study, we reported that consumption of grape powder by obese human subjects increased the production of the proinflammatory cytokines interleukin (IL)-1β and IL-6 by peripheral blood monocytes after ex vivo stimulation with bacterial lipopolysaccharide compared with the placebo treatment. We hypothesized that dietary grape powder increased the production of these cytokines by stimulated monocytes. To test this hypothesis, we used 24-hour dietary recall data to determine if differences in dietary patterns played a role in increased cytokine production. No differences in total energy, protein, carbohydrates, or fat intake in the diets were observed between the grape powder and placebo intervention periods. There were no differences observed in consumption of meats and poultry, eggs, fish, vegetables, grains, total dairy, or nuts and seeds by the participants between the 2 intervention periods. When participants received the grape powder, the recall data showed decreased intakes of butyric and capric acids (P<.05), and a possible trend toward decreased intake of cheese and total fruit (P<.1). Positive associations between the intakes of margaric acid, butter, total dairy, or whole grain and IL-6 production were observed (P<.05). However, path analysis showed that total energy, protein, carbohydrates, and fats, and individual fatty acids did not influence the production of cytokines by monocytes. The path analysis indicated that the increased cytokine production by lipopolysaccharide-stimulated monocytes from obese human subjects was caused by the grape powder and not mediated by differences in dietary intake.

Moderators of intervention dose effects on diet quality and physical activity changes in a church-based, multicomponent, lifestyle study: Delta Body and Soul III

Many community-based lifestyle interventions targeting African Americans have reported positive effects on participants' dietary choices and physical activity habits. However, these effects vary and not all participants will have outcome changes. Moderation analysis can help explain differential effects observed, but are not often reported. Hence, the objective of this secondary analysis was to explore potential moderators of intervention dose effects on diet quality and physical activity outcomes in an effective lifestyle intervention. Delta Body and Soul III, conducted from 2011 to 2012, was a 6-month, church-based, multicomponent, educational intervention designed to improve diet quality and increase physical activity in rural Southern African American adults. Generalized linear mixed models were used to determine associations among indicators of intervention dose received by participants, potential moderators and health outcome changes. Results indicated only three baseline characteristics-employment status, food shopping frequency and individual with primary responsibility for meal preparation-moderated the effects of education session attendance on diet quality changes. No evidence for moderation of exercise class attendance effects on physical activity changes was found. Thus, this culturally targeted, multicomponent lifestyle intervention did induce positive health changes in participants with a range of sociodemographic characteristics and food shopping and eating behaviors.

Psychosocial constructs were not mediators of intervention effects for dietary and physical activity outcomes in a church-based lifestyle intervention: Delta Body and Soul III

OBJECTIVE

Evaluating an intervention's theoretical basis can inform design modifications to produce more effective interventions. Hence the present study's purpose was to determine if effects from a multicomponent lifestyle intervention were mediated by changes in the psychosocial constructs decisional balance, self-efficacy and social support.

DESIGN

Delta Body and Soul III, conducted from August 2011 to May 2012, was a 6-month, church-based, lifestyle intervention designed to improve diet quality and increase physical activity. Primary outcomes, diet quality and aerobic and strength/flexibility physical activity, as well as psychosocial constructs, were assessed via self-report, interviewer-administered surveys at baseline and post intervention. Mediation analyses were conducted using ordinary least squares (continuous outcomes) and maximum likelihood logistic (dichotomous outcomes) regression path analysis.

SETTING

Churches (five intervention and three control) were recruited from four counties in the Lower Mississippi Delta region of the USA.

SUBJECTS

Rural, Southern, primarily African-American adults (n 321).

RESULTS

Based upon results from the multiple mediation models, there was no evidence that treatment (intervention v. control) indirectly influenced changes in diet quality or physical activity through its effects on decisional balance, self-efficacy and social support. However, there was evidence for direct effects of social support for exercise on physical activity and of self-efficacy for sugar-sweetened beverages on diet quality.

CONCLUSIONS

Results do not support the hypothesis that the psychosocial constructs decisional balance, self-efficacy and social support were the theoretical mechanisms by which the Delta Body and Soul III intervention influenced changes in diet quality and physical activity.

Association between Self-Weighing and Percent Weight Change: Mediation Effects of Adherence to Energy Intake and Expenditure Goals

BACKGROUND

To date, no investigators have examined electronically recorded self-weighing behavior beyond 9 months or the underlying mechanisms of how self-weighing might impact weight change.

OBJECTIVE

Our aims were to examine electronically recorded self-weighing behavior in a weight-loss study and examine the possible mediating effects of adherence to energy intake and energy expenditure (EE) goals on the association between self-weighing and weight change.

DESIGN

This was a secondary analysis of the self-efficacy enhancement arm of the Self Efficacy Lifestyle Focus (SELF) trial, an 18-month randomized clinical trial.

PARTICIPANTS/SETTING

The study was conducted at the University of Pittsburgh (2008-2013). Overweight or obese adults with at least one additional cardiovascular risk factor were eligible.

INTERVENTION

Participants in the self-efficacy enhancement arm were given a scale (Carematix, Inc) and instructed to weigh themselves at least 3 days per week or every other day. The scale date- and time-stamped each weighing episode, storing up to 100 readings.

MAIN OUTCOME MEASURES

Weight was assessed every 6 months. Adherence to energy intake and EE goals was calculated on a weekly basis using paper diary data.

STATISTICAL ANALYSES PERFORMED

Linear mixed modeling and mediation analyses were used.

RESULTS

The sample (n=55) was 80% female, 69% non-Hispanic white, mean (standard deviation) age was 55.0 (9.6) years and body mass index (calculated as kg/m2) was 33.1 (3.7). Adherence to self-weighing declined over time (P<0.001). From baseline to 6 months, there was a significant mediation effect of adherence to energy intake (P=0.02) and EE goals (P=0.02) on the association between adherence to self-weighing and percent weight change. Mediation effects were not significant during the second and third 6-month periods of the study.

CONCLUSIONS

Objectively measured adherence to self-weighing declined over 18 months. During the first 6 months, self-weighing directly impacted weight change and indirectly impacted weight change through changes in energy intake and EE.

Mediators of improved child diet quality following a health promotion intervention: the Melbourne InFANT Program

BACKGROUND

Young children's diets are currently suboptimal. Given that mothers have a critical influence on children' diets, they are typically a target of interventions to improve early childhood nutrition. Understanding the maternal factors which mediate an intervention's effect on young children's diets is important, but has not been well investigated. This research aimed to test whether maternal feeding knowledge, maternal feeding practices, maternal self-efficacy, and maternal dietary intakes acted as mediators of the effect of an intervention to improve child diet quality.

METHODS

The Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program was a cluster-randomized controlled trial, conducted from 2008-2010. This novel, low-dose, health promotion intervention was delivered quarterly over 15 months and involved educational activities, promotion of peer discussion, a DVD and written materials. Post-intervention, when children were approximately 18 months of age, child diets were assessed using multiple 24-hour recalls and a purpose-developed index of diet quality, the Obesity Protective Dietary Index. Maternal mediators were assessed using a combination of previously validated and purpose-deigned tools. Mediation analysis was conducted using the test of joint significance and difference of coefficients methods.

RESULTS

Across 62 parents' groups in Melbourne, Australia, 542 parents were recruited. Post- intervention, higher maternal feeding knowledge and lower use of foods as rewards was found to mediate the direct intervention effect on child diet quality. While other aspects of maternal feeding practices, self-efficacy and dietary intakes did not act as mediators, they were associated with child diet quality.

CONCLUSIONS

Mediation analysis of this novel health promotion intervention showed the importance of maternal feeding knowledge and use of foods as rewards in impacting child diet quality. The other maternal factors assessed were appropriate targets but further research on how to impact these in an intervention is important. This evidence of intervention efficacy and mediation provides important insights for planning future interventions.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN81847050, registered 23 November 2007.

Compliance to step count and vegetable serve recommendations mediates weight gain prevention in mid-age, premenopausal women. Findings of the 40-Something RCT

The 40-Something RCT aimed to determine if a 12-month health professional-led intervention could modify diet and physical activity behaviour for obesity prevention, in 44-50 year old, non-obese (BMI = 18.5-29.9 kg/m(2)) premenopausal women. Women were monitored for an additional 12 months to determine if effects could be maintained. This paper aimed to explore dietary and physical activity behavioural mediators hypothesised to be causally associated with weight change. Fifty-four women were randomised to a Motivational Interviewing Intervention (MI) (n = 28; five health professional consultations) or a Self-Directed Intervention (n = 26; written advice). Compliance to 10 study recommendations was measured at three months by a four-day weighed food and physical activity record including pedometer-measured step counts, self-reported exercise minutes and sitting time. The 10 compliance scores were independently assessed in mediation models for 12- and 24-month weight change. The MI effect on step count was an increase of 0.99 points on the 10-point compliance scale (p ≤ 0.01). This MI effect on step count significantly mediated the 12 and 24 month effect on weight (12 months AB = -0.74, 95%CI = -1.95, -0.14; 24 months AB = -1.06, 95% CI = -2.56, -0.36), accounting for 37.23% and 53.79% of the effect, respectively. The MI effect on vegetable serves was an increase of 1.50 points on the compliance scale (p = 0.02). The MI effect on vegetable compliance significantly mediated the effect on weight at 24 months (AB = -0.54, 95% CI = -1.50, -0.04), accounting for 24.92% of the effect. The remaining eight dietary and physical activity compliance scores did not significantly mediate weight loss. Encouraging women to take 10,000 steps and eat five vegetable serves per day may be a promising strategy to achieve long-term weight control at mid-life.

Social embeddedness as a mechanism for linking social cohesion to well-being among older adults: moderating effect of gender

BACKGROUND

The positive effect of social cohesion on well-being in older adults has been well documented. However, relatively few studies have attempted to understand the mechanisms by which social cohesion influences well-being. The main aim of the current study is to identify social pathways in which social cohesion may contribute to well-being.

METHODS

The data for this study (taken from 1,880 older adults, aged 60 years and older) were drawn from a national survey conducted during 2008-2009. The survey employed a two-stage stratified sampling process for data collection. Structural equation modeling was used to test mediating and moderating analyses.

RESULTS

The proposed model documented a good fit to the data (GFI =98; CFI =0.99; RMSEA =0.04). The findings from bootstrap analysis and the Sobel test revealed that the impact of social cohesion on well-being is significantly mediated by social embeddedness (Z=5.62; P<0.001). Finally, the results of a multigroup analysis test showed that social cohesion influences well-being through the social embeddedness mechanism somewhat differently for older men than women.

CONCLUSION

The findings of this study, in addition to supporting the importance of neighborhood social cohesion for the well-being of older adults, also provide evidence that the impact of social cohesion towards well-being is mediated through the mechanism of social embeddedness.

A health promotion intervention can affect diet quality in early childhood

Initiatives to promote children's nutrition and prevent childhood obesity are vital. Dietary patterns are a useful way to characterize whole diets, though no previous early childhood health promotion trial to our knowledge has assessed intervention impact using this approach. This research aimed to assess the effect of a healthy eating and physical activity intervention on young children's dietary patterns. The Melbourne Infant Feeding Activity and Nutrition Trial Program was a health promotion, cluster-randomized controlled trial involving 542 families. Child diets were assessed by multiple 24-h recalls postintervention at ~18 mo of age. An Obesity Protective Dietary Index (OPDI) was created and dietary patterns were also assessed by principal components analysis (PCA). These outcomes were used to compare intervention and control participants to test the effectiveness of the intervention. Children in the intervention arm scored higher (15.6 ± 5.9) than those in the control arm (14.5 ± 6.7) for the OPDI (scores out of 30, P = 0.01). Three dietary patterns were identified by PCA; however, the scores did not substantially differ between the intervention and control arms. In conclusion, this paper presents novel results in both the evaluation of an early childhood health promotion intervention and the assessment of child dietary patterns. The results highlight the capacity for such an initiative to improve child diets and the need for further research in this area.

Enhanced understanding of the relationship between erection and satisfaction in ED treatment: application of a longitudinal mediation model

To apportion the direct effect and the indirect effect (through erections) that sildenafil (vs placebo) has on individual satisfaction and couple satisfaction over time, longitudinal mediation modeling was applied to outcomes on the Sexual Experience Questionnaire. The model included data from weeks 4 and 10 (double-blind phase) and week 16 (open-label phase) of a controlled study. Data from 167 patients with erectile dysfunction (ED) were available for analysis. Estimation of statistical significance was based on bootstrap simulations, which allowed inferences at and between time points. Percentages (and corresponding 95% confidence intervals) for direct and indirect effects of treatment were calculated using the model. For the individual satisfaction and couple satisfaction domains, direct treatment effects were negligible (not statistically significant) whereas indirect treatment effects via the erection domain represented >90% of the treatment effects (statistically significant). Week 4 vs week 10 percentages of direct and indirect effects were not statistically different, indicating that the mediation effects are longitudinally invariant. As there was no placebo arm in the open-label phase, mediation effects at week 16 were not estimable. In conclusion, erection has a crucial role as a mediator in restoring individual satisfaction and couple satisfaction in men with ED treated with sildenafil.

The Eating Identity Type Inventory (EITI). Development and associations with diet

People with healthy eating identities report healthier diets and demonstrate greater receptivity to nutrition interventions, but other types of eating identity are likely important. We developed the Eating Identity Type Inventory (EITI) to assess affinity with four eating identity types; healthy, meat, picky, and emotional. This study assessed factorial validity, using confirmatory factor analysis (CFA) and established reliability and convergent validity of the EITI. In a telephone survey, 968 primary household food shoppers completed the EITI and a dietary questionnaire; 101 repeated the EITI approximately 1month later.CFA revealed that an 11-item model provided acceptable fit (χ(2)=206; df=38), CFI=.938, NNFI=.925, RMSEA=.070; SRMR=.059). The EITI demonstrated acceptable internal consistencies with Cronbach alpha's ranging from .61 to .82 and good test-retest reliability for healthy, emotional, and picky types (Pearson's correlations ranging from .78 to .84). Ordinary Least Squares (OLS) used to assess relationships between eating identity type and diet analyses demonstrated significant hypothesized relationships between healthy eating identity and healthier dietary intake and meat and picky eating identities and less healthy dietary intake. The EITI could facilitate behavioral and cognitive research to yield important insights for ways to more effectively design messages, interventions, and policies to promote healthy dietary behaviors.

Adherence to a Mediterranean dietary pattern in early life is associated with lower arterial stiffness in adulthood: the Amsterdam Growth and Health Longitudinal Study

OBJECTIVES

To investigate whether adherence to a Mediterranean dietary pattern during adolescence and early adulthood affects arterial stiffness in adulthood, and the extent to which any such association may be attributed to a beneficial impact of this diet on cardiovascular disease risk factors such as blood pressure, central fatness and dyslipidaemia.

SETTING

The Amsterdam Growth and Health Longitudinal Study.

DESIGN AND SUBJECTS

We compared longitudinal levels of adherence to a Mediterranean dietary pattern (aMED score with range 0-9) during adolescence and adulthood (two to eight repeated measures obtained between the ages of 13 and 36) between individuals with different levels of arterial stiffness in adulthood. The study population included 373 (196 women) apparently healthy adults in whom properties of the carotid, brachial and femoral arteries were assessed using ultrasonography at 36 years of age.

RESULTS

After adjustments for potential confounders, individuals with stiffer carotid arteries (defined on the basis of the most adverse tertile of, for instance, the distensibility coefficient) had lower aMED scores (-0.32, 95% CI -0.60; -0.06) and were less likely to have adhered to this dietary pattern (aMED score ≥5, odds ratio 0.69, 95% CI 0.50; -0.94) during the preceding 24 years compared with those with less stiff arteries. Differences in aMED scores were already present in adolescence and were only in part explained by the favourable associations between the Mediterranean dietary pattern and other cardiovascular disease risk factors (up to 26%), particularly mean blood pressure (up to 19%).

CONCLUSIONS

Promoting the Mediterranean diet in adolescence and early adulthood may constitute an important means of preventing arterial stiffness in adulthood.

Vitamin e and the healing of bone fracture: the current state of evidence

Background. The effect of vitamin E on health-related conditions has been extensively researched, with varied results. However, to date, there was no published review of the effect of vitamin E on bone fracture healing. Purpose. This paper systematically audited past studies of the effect of vitamin E on bone fracture healing. Methods. Related articles were identified from Medline, CINAHL, and Scopus databases. Screenings were performed based on the criteria that the study must be an original study that investigated the independent effect of vitamin E on bone fracture healing. Data were extracted using standardised forms, followed by evaluation of quality of reporting using ARRIVE Guidelines, plus recalculation procedure for the effect size and statistical power of the results. Results. Six animal studies fulfilled the selection criteria. The study methods were heterogeneous with mediocre reporting quality and focused on the antioxidant-related mechanism of vitamin E. The metasynthesis showed α-tocopherol may have a significant effect on bone formation during the normal bone remodeling phase of secondary bone healing. Conclusion. In general, the effect of vitamin E on bone fracture healing remained inconclusive due to the small number of heterogeneous and mediocre studies included in this paper.

Explaining the effects of a point-of-purchase nutrition-information intervention in university canteens: a structural equation modelling analysis

Background

The importance of canteen meals in the diet of many university students makes the provision of simple point-of-purchase (POP) nutrition information in university canteens a potentially effective way to promote healthier diets in an important group of young adults. However, modifications to environments such as the posting of POP nutrition information in canteens may not cause an immediate change in meal choices and nutrient intakes. The present study aimed at understanding the process by which the POP nutrition information achieved its effects on the meal choice and energy intake, and whether the information was more effective in changing the meal choice of subgroups of university canteen customers.

Methods

The POP nutrition-information intervention used a one-group pretest-posttest design. A sample of 224 customers of two university canteens completed the baseline and 6-months follow-up surveys. A multi-group structural equation modelling analysis was used to test mediation effects of individual difference variables (liking, understanding and use of the information, subjective knowledge and attitude) on the energy intake from canteen meals, moderated by the objective nutrition knowledge and motivation to change diet.

Results

Significant relations were identified between liking of the information and its use on one hand and a positive effect in attitude towards healthy canteen meals on the other hand. Motivation to change diet and sufficient objective nutrition knowledge were required to maintain a recommended energy intake from canteen meals or to lead to a decrease in energy intake. Participants with greater objective nutrition knowledge had a greater understanding of the POP nutrition information which also resulted in a more effective use of the information.

Conclusions

The results suggest that nutrition-information interventions may be more effective when using nutrition information that is generally liked by the target population in combination with an educational intervention to increase objective nutrition knowledge.

Trial registration

NCT01249508

Usual energy intake mediates the relationship between food reinforcement and BMI

The relative reinforcing value of food (RRV(food)) is positively associated with energy consumed and overweight status. One hypothesis relating these variables is that food reinforcement is related to BMI through usual energy intake. Using a sample of two hundred fifty-two adults of varying weight and BMI levels, results showed that usual energy intake mediated the relationship between RRV(food) and BMI (estimated indirect effect = 0.0027, bootstrapped 95% confidence intervals (CIs) 0.0002-0.0068, effect ratio = 0.34), controlling for age, sex, minority status, education, and reinforcing value of reading (RRV(reading)). Laboratory and usual energy intake were correlated (r = 0.24, P < 0.001), indicating that laboratory energy intake could provide an index of eating behavior in the natural environment. The mediational relationship observed suggests that increasing or decreasing food reinforcement could influence body weight by altering food consumption. Research is needed to develop methods of modifying RRV(food) to determine experimentally whether manipulating food reinforcement would result in changes in body weight.

Investigating clinical heterogeneity in systematic reviews: a methodologic review of guidance in the literature

BACKGROUND

While there is some consensus on methods for investigating statistical and methodological heterogeneity, little attention has been paid to clinical aspects of heterogeneity. The objective of this study is to summarize and collate suggested methods for investigating clinical heterogeneity in systematic reviews.

METHODS

We searched databases (Medline, EMBASE, CINAHL, Cochrane Library, and CONSORT, to December 2010) and reference lists and contacted experts to identify resources providing suggestions for investigating clinical heterogeneity between controlled clinical trials included in systematic reviews. We extracted recommendations, assessed resources for risk of bias, and collated the recommendations.

RESULTS

One hundred and one resources were collected, including narrative reviews, methodological reviews, statistical methods papers, and textbooks. These resources generally had a low risk of bias, but there was minimal consensus among them. Resources suggested that planned investigations of clinical heterogeneity should be made explicit in the protocol of the review; clinical experts should be included on the review team; a set of clinical covariates should be chosen considering variables from the participant level, intervention level, outcome level, research setting, or others unique to the research question; covariates should have a clear scientific rationale; there should be a sufficient number of trials per covariate; and results of any such investigations should be interpreted with caution.

CONCLUSIONS

Though the consensus was minimal, there were many recommendations in the literature for investigating clinical heterogeneity in systematic reviews. Formal recommendations for investigating clinical heterogeneity in systematic reviews of controlled trials are required.

Lower lifetime dietary fiber intake is associated with carotid artery stiffness: the Amsterdam Growth and Health Longitudinal Study

BACKGROUND

Fiber intake is associated with lower cardiovascular disease risk. Whether arterial stiffness is influenced by lifetime fiber intake is not known. Any such association could explain, at least in part, the cardioprotective effects attributed to fiber intake.

OBJECTIVE

The objective was to investigate whether a lower intake of fiber (and fiber-rich foods) throughout the course of young life (ie, from adolescence to adulthood) is associated with arterial stiffness in adulthood.

DESIGN

This was a longitudinal cohort study among 373 participants in whom dietary intake was assessed between the ages of 13 to 36 y (2-8 repeated measures, median of 5), and arterial stiffness estimates of 3 large arteries (ultrasonography) were ascertained at age 36 y.

RESULTS

After adjustment for sex, height, total energy intake, and other lifestyle variables, subjects with stiffer carotid arteries consumed less fiber (in g/d) during the 24-y study than did those with less stiff carotid arteries, as defined on the basis of the highest compared with the lowest sex-specific tertiles of the distensibility and compliance coefficients (reversed) and Young's elastic modulus: -1.9 (95% CI: -3.1, -0.7), -2.3 (-3.5, -1.1), and -1.3 (-2.5, -0.0), respectively. Furthermore, subjects with stiffer carotid arteries were characterized by a lower lifetime consumption of fruit, vegetables, and whole grains-deleterious associations that could be explained, to a great extent, by related low fiber intake.

CONCLUSIONS

Lower lifetime intake of fiber during the course of young age is associated with carotid artery stiffness in adulthood. Promoting consumption of fiber-rich foods among the young may offer a means to prevent accelerated arterial stiffening in adulthood and related cardiovascular sequelae.

Evaluating MyPlate: an expanded framework using traditional and nontraditional metrics for assessing health communication campaigns

MyPlate, the icon and multimodal communication plan developed for the 2010 Dietary Guidelines for Americans (DGA), provides an opportunity to consider new approaches to evaluating the effectiveness of communication initiatives. A review of indicators used in assessments for previous DGA communication initiatives finds gaps in accounting for important intermediate and long-term outcomes. This evaluation framework for the MyPlate Communications Initiative builds on well-known and underused models and theories to propose a wide breadth of observations, outputs, and outcomes that can contribute to a fuller assessment of effectiveness. Two areas are suggested to focus evaluation efforts in order to advance understanding of the effectiveness of the MyPlate Communications Initiative: understanding the extent to which messages and products from the initiative are associated with positive changes in social norms toward the desired behaviors, and strategies to increase the effectiveness of communications about DGA in vulnerable populations.

Mediators of weight loss in the 'Healthy Dads, Healthy Kids' pilot study for overweight fathers

BACKGROUND

A poor understanding of the specific lifestyle behaviors that result in weight loss has hindered the development of effective interventions. The aim of this paper was to identify potential behavioral mediators of weight loss in the Healthy Dads, Healthy Kids (HDHK) intervention for overweight fathers.

FINDINGS

The three-month intervention was evaluated in a randomized controlled trial and conducted in Newcastle, New South Wales, Australia. Baseline, three month (immediate post-intervention) and six month assessments were conducted. Recruitment and follow-up occurred between October 2008 and May 2009. The study sample included 53 overweight/obese men [mean ( SD) age=40.6( 97.1) years; body mass index (BMI)=33.2 (3.9) kgm-2] and their primary school-aged children [n=71, 54% boys; age=8.2 (2.0) years] who were randomized to HDHK program or a wait-list control group. Physical activity (PA) was assessed using pedometers and dietary behaviors were measured using a validated food frequency questionnaire. The intervention resulted in significant weight loss (5.131.27 kg, P<0.0001) and increased PA among fathers (2769750 steps/day, P<0.001) and their children (1486521 steps/day, P<0.01). Fathers PA mediated weight loss in the intervention (AB=2.31, 95% CI=4.63 to 0.67) and was responsible for 47% of the intervention effect. Changes in dietary behaviors were not statistically significant.

CONCLUSIONS

PA was an important mediator of weight loss in the HDHK intervention. Encouraging overweight fathers to be more active with their children appears to be a promising strategy for obesity treatment in men.

Mediators of weight loss in the 'Healthy Dads, Healthy Kids' pilot study for overweight fathers

Background

A poor understanding of the specific lifestyle behaviors that result in weight loss has hindered the development of effective interventions. The aim of this paper was to identify potential behavioral mediators of weight loss in the Healthy Dads, Healthy Kids (HDHK) intervention for overweight fathers.

Findings

The three-month intervention was evaluated in a randomized controlled trial and conducted in Newcastle, New South Wales, Australia. Baseline, three month (immediate post-intervention) and six month assessments were conducted. Recruitment and follow-up occurred between October 2008 and May 2009. The study sample included 53 overweight/obese men [mean ( SD) age=40.6( 97.1) years; body mass index (BMI)=33.2 (3.9) kgm^-2] and their primary school-aged children [n=71, 54% boys; age=8.2 (2.0) years] who were randomized to HDHK program or a wait-list control group. Physical activity (PA) was assessed using pedometers and dietary behaviors were measured using a validated food frequency questionnaire. The intervention resulted in significant weight loss (5.131.27kg, P<0.0001) and increased PA among fathers (2769750 steps/day, P<0.001) and their children (1486521 steps/day, P<0.01). Fathers PA mediated weight loss in the intervention (AB=2.31, 95% CI=4.63 to 0.67) and was responsible for 47% of the intervention effect. Changes in dietary behaviors were not statistically significant.

Conclusions

PA was an important mediator of weight loss in the HDHK intervention. Encouraging overweight fathers to be more active with their children appears to be a promising strategy for obesity treatment in men.

The PHLAME (Promoting Healthy Lifestyles: Alternative Models' Effects) firefighter study: testing mediating mechanisms

This paper examines the mechanisms by which PHLAME (Promoting Healthy Lifestyles: Alternative Models' Effects), a health promotion intervention, improved healthy eating and exercise behavior among firefighters, a population at high risk for health problems due to occupational hazards. In a randomized trial, 397 firefighters participated in either the PHLAME team intervention with their work shift or a control condition. Intervention sessions taught benefits of a healthy diet and regular exercise, and sought to improve social norms and social support from coworkers for healthy behavior. At posttest, team intervention participants had increased their fruit and vegetable consumption as compared to control participants. An increase in knowledge of fruit and vegetable benefits and improved dietary coworker norms partially mediated these effects. Exercise habits and VO2 max were related to targeted mediators but were not significantly changed by the team intervention. Partial support was found for both the action and conceptual theories underlying the intervention. Our findings illustrate how an effective program's process can be deconstructed to understand the underpinnings of behavior change and refine interventions. Further, fire stations may improve the health of firefighters by emphasizing the benefits of healthy diet and exercise behaviors while also encouraging behavior change by coworkers as a whole.

The IGNITE (investigation to guide new insight into translational effectiveness) trial: Protocol for a translational study of an evidenced-based wellness program in fire departments

BACKGROUND

Worksites are important locations for interventions to promote health. However, occupational programs with documented efficacy often are not used, and those being implemented have not been studied. The research in this report was funded through the American Reinvestment and Recovery Act Challenge Topic 'Pathways for Translational Research,' to define and prioritize determinants that enable and hinder translation of evidenced-based health interventions in well-defined settings.

METHODS

The IGNITE (investigation to guide new insights for translational effectiveness) trial is a prospective cohort study of a worksite wellness and injury reduction program from adoption to final outcomes among 12 fire departments. It will employ a mixed methods strategy to define a translational model. We will assess decision to adopt, installation, use, and outcomes (reach, individual outcomes, and economic effects) using onsite measurements, surveys, focus groups, and key informant interviews. Quantitative data will be used to define the model and conduct mediation analysis of each translational phase. Qualitative data will expand on, challenge, and confirm survey findings and allow a more thorough understanding and convergent validity by overcoming biases in qualitative and quantitative methods used alone.

DISCUSSION

Findings will inform worksite wellness in fire departments. The resultant prioritized influences and model of effective translation can be validated and manipulated in these and other settings to more efficiently move science to service.