Does recommending healthy diets in general practice benefit secondary prevention of cardiovascular disease? A systematic review and meta-analysis.

Abstract (English)

BACKGROUND: Suboptimal diet is the main preventable risk factor globally for cardiovascular disease (CVD), posing major burden for primary care. However, healthy dietary recommendations' evidence in patients with established CVD is unclear. AIM: Systematically review and meta-analyse dietary patterns' effect on CVD patients' all-cause and CVD mortality, and CVD recurrence. METHOD: Publication databases were searched for randomised controlled trials (RCTs) (≥6 months follow-up) and prospective cohort studies. Random-effects meta-analysis calculated relative-risks (RR) and 95% confidence-intervals (95% CI). Cochrane bias risk tools assessed study quality. RESULTS: Screening 28 291 abstracts identified 41 articles meeting inclusion criteria. Nineteen articles from 14 unique RCTs conducted 1956-2020, enrolling 14 065 CVD patients, compared fat-replacement, Mediterranean, low-fat, low-sodium, and high-fibre diets with minimal/no dietary advice. Pooled results showed no diet intervention significantly impacted mortality/CVD outcomes. However, stratified meta-analysis revealed a Mediterranean-diet significantly reduced CVD mortality (RR: 0.40; 95% CI: 0.19, 0.83). Twenty-two cohort studies, conducted 1976-2017 for 104 386 CVD patients, predominantly assessed a Mediterranean diet (60%), showing greatest healthy dietary pattern adherence significantly reduced all-cause mortality by 29% (0.71; 0.65, 0.78), CVD mortality by 25% (0.75; 0.66, 0.84), and CVD recurrence by 17% (0.83; 0.75, 0.92). Overall, there was considerable between-study heterogeneity (RCTs: I² = 34-60%, cohorts: I² = 49-76%) partly explained by disparate geographical locations, and studies were mainly classified as of some concerns (65% RCTs) or high bias risk (52% cohorts). CONCLUSION: GPs providing healthy dietary advice, particularly the Mediterranean diet, likely enhances CVD secondary prevention. However, cogent studies with clearly defined diets are required to bolster the evidence.