Abstract P606: Effectiveness of Randomized Dietary Interventions for the Primary Prevention of Incident Cardiovascular Disease and Type 2 Diabetes

Abstract

Objective: Randomized controlled trials (RCTs) provide opportunities to estimate the causal effects of interventions on disease risk; however, large-scale, long-term RCTs of diet for the prevention of major chronic disease endpoints are sparse. We sought to summarize RCTs comparing the effectiveness of dietary interventions for the primary prevention of clinical cardiovascular disease (CVD) events and type 2 diabetes (T2D) in adults. Methods: We conducted a systematic review and meta-analysis (PROSPERO #CRD42021283728) of RCTs exclusively with dietary interventions with outcomes of incident primary CVD events and/or T2D among adults. We searched MEDLINE and other databases and references. Eligible interventions included those providing instruction, education, and/or provisions to modify intakes of nutrients, foods, or overall dietary patterns. We excluded meal replacement products, dietary supplements, interventions with concomitant comprehensive lifestyle programs, exercise regimens, etc., trials in secondary prevention populations, and trials assessing risk factor or biomarker changes only, rather than clinical events. Two investigators performed screening and data extraction in parallel. We conducted a random effects meta-analysis to estimate the pooled effectiveness of dietary interventions compared with usual diet or low-fat control groups for CVD and T2D outcomes, separately. Results: Among the 5365 citations generated in our searches, we identified 4 eligible RCTs, representing 56,721 participants with mean ages ranging from 44.7 to 67.9 years. Mean intervention duration was 2.3 to 8.1 years, resulting in 3,151 CVD events and 3,603 T2D cases. Compared with the control diets, the various healthy dietary patterns were related to a combined 7% (relative risk [RR] = 0.93, confidence interval [CI] = 0.87-1.00) lower CVD risk and 8% (RR = 0.92, CI = 0.86-0.98) lower T2D risk. Conclusion: Despite major morbidity and mortality from CVD and T2D, there have been few large, population-based, long-term RCTs assessing the exclusive effectiveness of dietary modification for the primary prevention of clinical CVD events or T2D. Results, however, indicate that various healthy diets may be modestly effective for primary prevention.