Table 1.
Characteristics of systematic and comprehensive narrative reviews on egg intake and CVD and/or diabetes
| Reference | Objective | Database/Publication years | Search terms*/Inclusion criteria | Included studies | Conclusions | Quality Rating† |
|---|---|---|---|---|---|---|
| Geiker et al. 2018(22) | Assess the recommendation to lower the dietary intake of cholesterol and especially the intake of egg to reduce the risk of CVD and T2DM |
Database: nr Years: within last 10 y of April–May 2015 (also included past MAs) |
Terms: egg, cholesterol, diabetes, cardiovascular Criteria: human studies published in English investigating the effect of egg consumption on risk markers of CVD or T2DM |
Sixteen PC and five other observational studies (sixteen CVD, six T2DM) Twenty-three intervention studies, all on CVD or relevant biomarker (e.g. blood lipids) |
≤7 eggs per week can safely be consumed, but in patients with established CVD or T2DM only with special emphasis on a healthy lifestyle. Intervention studies have not reported associations between increased egg consumption and risk markers for CVD and T2DM, whereas observational studies have found associations. Risk association in observational studies are more likely to be attributed to diet and lifestyle patterns and/or clusters of other risk factors in high-egg consumers. | PRISMA: 58 % ROBIS: Unclear Bias AMSTAR2: 15 % |
| Park et al., 2018(23) | Summarize the literature on egg consumption and the risk of metabolic disease. |
Database: PubMed, Embase Years: published through Dec. 2017 |
Terms: egg intake, egg consumption, metabolic syndrome, CHD, CVD, diabetes mellitus Criteria: nr |
Five RCT (three T2DM/MetS, two biomarkers); eighteen PC (nine T2DM/MetS, eight CVD or related, one both); three cross-sectional (two T2DM/MetS, one CVD) |
The literature review found conflicting results, with all three cross-sectionals, ten PC studies, and all five RCTs showing evidence of null effect or decreased risk to metabolic diseases, while eight of the PC studies reported an increased risk to one or more metabolic disease outcome. (Note: A cross-sectional study was also reported within this publication and only data from the literature review is reported herein). | PRISMA: 58 % ROBIS: Unclear Bias AMSTAR2: 8 % |
| Mente et al., 2009(19) | Evaluate dietary exposures and CHD using Bradford Hill criteria, identify dietary exposures that have sufficient RCT data to support the PC findings, and determine those that have insufficient evidence for conclusions |
Database: MEDLINE Years: 1950 through June 2007 |
Terms: nr Criteria: RCT or PC study published in English on diet and heart disease that reported RR and CI after adjustment for confounders. PC had to include estimates of dietary intake and have ≥1 y follow-up. RCTs had to compare dietary intervention with a control or placebo. |
Six cohorts, representing 258, 221 patients, details nr | Weak evidence of causality for eggs and CHD, with only one of four Bradford Hill criteria met for potential causal relationship with coronary outcomes and secondary events. No evidence of linear dose-response relationship was found. | PRISMA 79 % ROBIS: High Bias AMSTAR2: 31 % |
| Kerley CP 2018(24); Kerley CP 2018(25) |
Provide a comprehensive summary of the current evidence regarding dietary patterns/components and HF |
Database: MEDLINE, CINAHL, EMBASE, Cochrane Years: published through Oct. 2017 |
Terms: heart failure, numerous dietary components, specific diets (e.g. paleo, Mediterranean, PREDIMED, DART, DASH, etc.) Criteria: human, non-pharma with HF outcome; excluded salt/Na, alcohol, fluid restriction, micronutrient supplementation, over- or undernutrition |
Three PC on HF and eggs | Two of the three PC studies reported a positive association between risk of HF and egg consumption, while the other was null. Data were consistent with a previous MA that reported an elevated risk of HF with higher egg consumption. | PRISMA: 47 %; 32 % ROBIS: High Bias; High Bias AMSTAR2: 8 %; 15 % |
| Richard et al. 2017(20) | Assess the impact of egg consumption on CVD risk factors in individuals with T2DM or at risk of developing T2DM (e.g. prediabetes, insulin resistance or having MetS) | Database: PubMed, MEDLINE, EMBASE, Web of Science Years: through January 2017, with updated search on July 2017 |
Terms: egg, diabetes, glucose, insulin, MetS, blood lipids, CRP Criteria: published in English, RCTs, eggs as sole dietary manipulation, biomarkers of glycaemic control and/or CVD risk, intervention at least 4 weeks |
Ten intervention studies (seven MetS/ prediabetes; three T2DM) | Results from RCTs suggest that consumption of 6–12 eggs/week, in the context of a diet that is consistent with guidelines on CV health promotion, has no adverse effect on major CVD risk factors (e.g. tChol, LDL-C, TG, FBG, insulin, CRP) in individuals at risk for developing diabetes or with T2DM, with some evidence for an increase in HDL-C. However, studies were heterogeneous in design, population, and interventions, preventing firm conclusions. | PRISMA: 89 % ROBIS: Low Bias AMSTAR2: 38 % |
| Tran et al. 2014(21) | Review epidemiological and experimental evidence on the relationship between egg consumption and CVD risks among T2DM individuals, and T2DM risk in non-diabetic subjects |
Database: PubMed Years: through Nov. 2013 |
Terms: egg(s), diabetes, MetS, glucose, insulin, stroke, myocardial, atherosclerosis, CVD, CHD, CAD, dietary cholesterol, blood lipids Criteria: human studies published in English, for intervention included egg or dietary cholesterol consumption and biomarkers of CHD or T2DM in adults ≥19 y |
Seven PC on egg and CVD risk in diabetics; ten observational (nine reports) on egg and T2DM risk; six intervention studies on egg and CHD risk in diabetics; nine intervention studies on egg and CVD/ T2DM markers in non-diabetics |
Significant association between egg consumption and CVD and mortality in T2DM subjects, and some evidence for an association between incident T2DM, but lack of adjustment for dietary confounders was common. Limited evidence from experimental studies was identified. Studies among healthy individuals found suggestive evidence that dietary interventions that included eggs may reduce the risk of T2DM and MetS. Overall, heterogeneity in study design and populations, small sample sizes, and lack of control for confounders limited conclusions. | PRISMA: 63 % ROBIS: High Bias AMSTAR2: 15 % |
CAD, coronary artery disease; CRP, C-reactive protein; CV, cardiovascular; FBG, fasting blood glucose; HDL-C, high-density lipoprotein cholesterol; HF, heart failure; LDL-C, low-density lipoprotein cholesterol; MA(s), meta-analysis(es); MetS, metabolic syndrome; nr, not reported; PC, prospective cohort; PRISMA, preferred reporting items for systematic reviews and meta-analyses; RCT, randomized controlled trial; ROBIS, risk of bias in systematic reviews; RR, relative risk; T2DM, type-2 diabetes mellitus; tChol, total-cholesterol; TG, triglycerides.
*
Terms summarized for comparison of scope or search. See specific reports for full list of search terms and combinations.
†
Details on PRISMA, ROBIS, and AMSTAR2 assessments are provided in the methods section. Briefly, AMSTAR2 checklist items were scored at 1-point if present and zero if missing, and final assessment scores were presented as a percentage of adjusted the maximum attainable scores (19 and 13 points, respectively), with a higher score indicating a higher quality. ROBIS assessments for systematic reviews did not include Domain 4, as it was not applicable to non-meta-analyses, and the overall assessment was adjusted accordingly, with low risk of bias indicating higher quality. Finally, adherence to the PRISMA checklist was presented as a percentage of the maximum attainable scores (19 for systematic reviews).