Abstract
To update the European Association for the Study of Diabetes clinical practice guidelines for nutrition therapy, we conducted an umbrella review and updated systematic review and meta-analysis (SRMA) of prospective cohort studies of the association between dietary pulses with or without other legumes and cardiometabolic disease outcomes. We searched the PubMed, MEDLINE, EMBASE, and Cochrane databases through March 2019. We included the most recent SRMAs of prospective cohort studies and new prospective cohort studies published after the census dates of the included SRMAs assessing the relation between dietary pulses with or without other legumes and incidence and mortality of cardiovascular diseases (CVDs) [including coronary heart disease (CHD), myocardial infarction (MI), and stroke], diabetes, hypertension, and/or obesity. Two independent reviewers extracted data and assessed risk of bias. Risk estimates were pooled using the generic inverse variance method and expressed as risk ratios (RRs) with 95% CIs. The overall certainty of the evidence was assessed using the GRADE approach. Six SRMAs were identified and updated to include 28 unique prospective cohort studies with the following number of cases for each outcome: CVD incidence, 10,261; CVD mortality, 16,168; CHD incidence, 7786; CHD mortality, 3331; MI incidence, 2585; stroke incidence, 8570; stroke mortality, 2384; diabetes incidence, 10,457; hypertension incidence, 83,284; obesity incidence, 8125. Comparing the highest with the lowest level of intake, dietary pulses with or without other legumes were associated with significant decreases in CVD (RR: 0.92; 95% CI: 0.85, 0.99), CHD (RR: 0.90; 95% CI: 0.83, 0.99), hypertension (RR: 0.91; 95% CI: 0.86, 0.97), and obesity (RR: 0.87; 95% CI: 0.81, 0.94) incidence. There was no association with MI, stroke, and diabetes incidence or CVD, CHD, and stroke mortality. The overall certainty of the evidence was graded as “low” for CVD incidence and “very low” for all other outcomes. Current evidence shows that dietary pulses with or without other legumes are associated with reduced CVD incidence with low certainty and reduced CHD, hypertension, and obesity incidence with very low certainty. More research is needed to improve our estimates. This trial was registered at clinicaltrials.gov as NCT03555734. Adv Nutr 2019;10:S308–S319.
Generated Summary
An umbrella review and updated systematic review and meta-analysis (SRMA) of prospective cohort studies was conducted to assess the association between dietary pulses, with or without other legumes, and cardiometabolic disease outcomes. The methodology followed the Cochrane Handbook and the Meta-analysis of Observational Studies in Epidemiology guideline. Data were extracted and risk of bias was assessed using the Newcastle-Ottawa Scale (NOS). The overall certainty of evidence was assessed using the GRADE approach. The study aimed to provide updated recommendations on the role of dietary pulses in preventing and managing cardiometabolic diseases. The review included SRMAs of prospective cohort studies and new prospective cohort studies published after the census dates of the included SRMAs, specifically evaluating the relationship between dietary pulses and outcomes such as cardiovascular diseases (CVDs), diabetes, hypertension, and obesity. Data extraction involved two independent reviewers. The primary outcome was incidence and/or mortality of CVDs, including coronary heart disease (CHD), myocardial infarction (MI), and stroke, while secondary outcomes included the incidence and/or mortality of diabetes, hypertension, and obesity. Statistical analyses involved primary and sensitivity analyses using Review Manager and STATA software. Subgroup and publication bias analyses were also conducted.
Key Findings & Statistics
- A total of 6 SRMAs were identified and updated to include 28 unique prospective cohort studies.
- The included studies had the following number of cases for each outcome: CVD incidence, 10,261; CVD mortality, 16,168; CHD incidence, 7786; CHD mortality, 3331; MI incidence, 2585; stroke incidence, 8570; stroke mortality, 2384; diabetes incidence, 10,457; hypertension incidence, 83,284; and obesity incidence, 8125.
- Comparing the highest with the lowest level of intake, dietary pulses with or without other legumes were associated with significant decreases in CVD (RR: 0.92; 95% CI: 0.85, 0.99), CHD (RR: 0.90; 95% CI: 0.83, 0.99), hypertension (RR: 0.91; 95% CI: 0.86, 0.97), and obesity (RR: 0.87; 95% CI: 0.81, 0.94) incidence.
- There was no association with MI, stroke, and diabetes incidence or CVD, CHD, and stroke mortality.
- The study found a protective association between dietary pulses with or without other legumes and CVD incidence (RR: 0.92; 95% CI: 0.85, 0.99; P = 0.03).
- For CHD incidence, the study found a protective association (RR: 0.90; 95% CI: 0.83, 0.99; P = 0.03).
- The analysis revealed no association between dietary pulses and CVD mortality (RR: 0.97; 95% CI: 0.89, 1.06; P = 0.53).
- There was no association between dietary pulses and CHD mortality (RR: 0.94; 95% CI: 0.82, 1.08; P = 0.39).
- No association was found between dietary pulses and MI incidence (RR: 0.90; 95% CI: 0.74, 1.10; P = 0.29).
- There was no association between dietary pulses and stroke incidence (RR: 0.98; 95% CI: 0.86, 1.11; P = 0.73).
- There was no association between dietary pulses and stroke mortality (RR: 0.89; 95% CI: 0.78, 1.03; P = 0.12).
- The study found no association between dietary pulses and diabetes incidence (RR: 0.93; 95% CI: 0.83, 1.05; P = 0.26).
- A protective association was found between dietary pulses and hypertension incidence (RR: 0.91; 95% CI: 0.86, 0.97; P = 0.002).
- A protective association was observed for obesity incidence (RR: 0.87; 95% CI: 0.81, 0.94; P trend < 0.0001).
- The majority of studies adjusted for key confounding variables: age, sex, family history of CVD, smoking, markers of overweight/obesity, energy intake, and physical activity.
Other Important Findings
- The evidence suggests that dietary pulses, whether alone or with other legumes, are linked to a reduced incidence of CVD.
- A protective association was also found between dietary pulses and a reduced incidence of CHD, hypertension, and obesity.
- There was no clear association between dietary pulses and mortality from CVD, CHD, or stroke.
- The study’s dose-response analysis revealed evidence of a linear dose-response gradient for the relationship between dietary pulses and CVD incidence.
- The analysis indicated no evidence of publication bias for the outcomes of CVD mortality and CHD incidence.
- The certainty of the evidence was assessed using the GRADE approach and graded as low for CVD incidence and very low for all other outcomes.
Limitations Noted in the Document
- The study acknowledges inherent limitations in observational studies, including the inability to completely rule out residual confounding.
- Potential confounders such as reverse causality, the reliability of self-reported intake, and the collinearity of dietary and lifestyle patterns are mentioned as limitations.
- Other limitations include the risk of bias, inconsistency between studies, and indirectness.
- The study notes that risk of bias could not be ruled out for hypertension incidence due to studies being considered high risk, and residual inconsistency for stroke and diabetes incidence was also noted.
- The indirectness could not be ruled out for hypertension incidence.
- The study acknowledged that a wide range of intake for dietary pulses existed across studies.
- The study points out that the estimates of pooled risk had limitations with the confidence intervals being wide and could not rule out clinically important benefit or harm across most of the outcomes.
- It was noted that only one cohort study was assessed, and no association was found with obesity risk.
Conclusion
The umbrella review and updated SRMA of prospective cohort studies support the consumption of dietary pulses with or without other legumes in the prevention of certain cardiometabolic diseases, including CVD, CHD, hypertension, and obesity. The certainty of this evidence is generally weak, underscoring the need for caution in drawing conclusions. Important sources of uncertainty include the risk of residual confounding in observational studies, which limits the ability to draw causal inferences, and potential indirectness in how dietary pulses were measured. Despite the limitations, the findings indicate that incorporating dietary pulses into a healthy dietary pattern can have benefits for improving cardiometabolic health. There was an 8-13% decrease in CVD, CHD, hypertension, and obesity incidence, when comparing highest and lowest level of intake. Further research should differentiate between various types of legumes in the exposure and analyze associations between dietary pulses and cardiometabolic outcomes separately to refine the understanding of these relationships. The current low levels of dietary pulse consumption highlight the opportunity to incorporate these foods more widely as part of a healthy diet. The consistent benefit of dietary pulses across different cardiometabolic outcomes underscores the importance of dietary recommendations. These insights are very important and can aid in the development of dietary guidelines and public health strategies. Addressing the limitations, improving the accuracy of intake measurements, and differentiating between legume types could further strengthen the evidence and clarify the role of dietary pulses in preventing and managing cardiometabolic diseases. Future studies should focus on improving these aspects to provide more precise estimates of the benefits and allow for more informed public health recommendations to reduce cardiometabolic risk.