Comparing dietary strategies to manage cardiovascular risk in primary care: a narrative review of systematic reviews

Background: Nutrition care in general practice is crucial for cardiovascular disease (CVD) prevention and management, although comparison between dietary strategies is lacking. 

Aim: To compare the best available (most recent, relevant, and high-quality) evidence for six dietary strategies that are effective for primary prevention/ absolute risk reduction of CVD. 

Design and setting: A pragmatic narrative review of systematic reviews of randomised trials focused on primary prevention of cardiovascular events. 

Method: Studies about: 1) adults without a history of cardiovascular events; 2) target dietary strategies postulated to reduce CVD risk; and 3) direct cardiovascular or all-cause mortality outcomes were included. Six dietary strategies were examined: energy deficit, Mediterranean-like diet, sodium reduction (salt reduction and substitution), the Dietary Approaches to Stop Hypertension (DASH) diet, alcohol reduction, and fish/fish oil consumption. Reviews were selected based on quality, recency, and relevance. Quality and certainty of evidence was assessed using GRADE. 

Results: Twenty-five reviews met inclusion criteria; eight were selected as the highest quality, recent, and relevant. Three dietary strategies showed modest, significant reductions in cardiovascular events: energy deficit (relative risk reduction [RRR] 30%, 95% confidence interval [CI] = 13 to 43), Mediterranean-like diet (RRR 40%, 95% CI = 20 to 55), and salt substitution (RRR 30%, 95% CI = 7 to 48). Still, some caveats remain on the effectiveness of these dietary strategies. Salt reduction, DASH diet, and alcohol reduction showed small, significant reductions in blood pressure, but no reduction in cardiovascular events. Fish/fish oil consumption showed little or no effect; supplementation of fish oil alone showed small reductions in CVD events. 

Conclusion: For primary prevention, energy deficit, Mediterranean-like diets, and sodium substitution have modest evidence for risk reduction of CVD events. Strategies incorporated into clinical nutrition care should ensure guidance is person centred and tailored to clinical circumstances.