DASH Diet for the Primary and Secondary Prevention of Cardiovascular Diseases

In adults, does adhering to the Dietary Approaches to Stop Hypertension (DASH) diet reduce rates of cardiovascular events (eg, myocardial infarction [MI], stroke) or all-cause mortality compared with usual diet or other dietary interventions?

The DASH diet does not appear to reduce the rates of cardiovascular events (ie, MI, stroke) or all-cause mortality over 4 to 18 months of follow-up compared with usual care or minimal dietary interventions (low-certainty evidence) in adults with no history of heart disease.¹ (Strength of Recommendation: B, limited-quality patient-oriented evidence.)

Cardiovascular disease (CVD) remains the leading cause of death globally, accounting for nearly one-third of all deaths worldwide, and it is also the top cause of death in the United States. Diet is a key modifiable risk factor.^2–4 The DASH diet emphasizes fruits, vegetables, whole grains, low-fat dairy, reduced sodium, and reduced saturated fat, and is endorsed by major cardiovascular guidelines for hypertension and general CVD prevention.⁴ The authors of this Cochrane review aimed to investigate whether the DASH diet reduces cardiovascular events compared with other dietary interventions.¹

This recent Cochrane review analyzed five randomized controlled trials (RCTs; n = 1,397) evaluating the DASH diet for primary prevention in adults 18 years and older (mean age = 34–53 years).¹ Trial durations ranged from 4 to 18 months. All trials were conducted in the United States or Poland. Control groups in these studies received no special dietary instruction (usual care) or minimal dietary intervention (ie, brief dietary advice or an informational pamphlet given during a medical visit). Participants were adults without established CVD, many of whom had elevated blood pressure (systolic = 120–159 mm Hg, diastolic = 80–95 mm Hg) and were not yet taking antihypertensive drugs. Standard medical therapy, including initiation of antihypertensive or lipid-lowering drugs when clinically indicated, was allowed to continue alongside dietary interventions. Notably, none of the included trials involved patients with existing CVD, so secondary prevention outcomes were not evaluated.¹

Cardiovascular events were uncommon across all five RCTs.¹ Several trials reported zero instances of MI or stroke in either group during the follow-up period. Overall, there were no significant differences in the rates of MI, stroke, or all-cause mortality between participants in the DASH diet group and those in the control groups. For example, in two trials (n = 629), cardiovascular event rates were minimal in the DASH and control arms, yielding no statistically detectable benefit of the DASH diet on clinical outcomes. No cardiovascular deaths were reported in the included trials; therefore, cardiovascular mortality was not analyzed. These null findings are attributable in part to the limited number of events and the short duration of the studies, which left them underpowered to detect differences in major clinical outcomes such as MI or stroke.¹

Although patient-oriented outcomes showed no improvement, the DASH diet did consistently produce favorable changes in disease-oriented intermediate measures.¹ Participants assigned to the DASH diet had greater reductions in blood pressure and improvements in their lipid profiles compared with those adhering to control diets. For instance, the DASH group reduced diastolic blood pressure by 2.20 mm Hg (one study; n = 90; 95% CI, −2.65 to −1.75 mm Hg), total cholesterol by 5.80 mg/dL (0.15 mmol/L; one study; n = 90; 95% CI, −8.28 to −3.32 mg/dL [−0.21 to −0.09 mmol/L]), triglyceride levels by 5.80 mg/dL (0.07 mmol/L; one study; n = 90; 95% CI, −9.73 to −1.87 mg/dL [−0.11 to −0.02 mmol/L), and increased high-density lipoprotein cholesterol by 2.20 mg/dL (0.06 mmol/L; one study; n = 90; 95% CI, 1.50–2.90 mg/dL [0.04 to 0.08 mmol/L). [corrected] There was little to no effect on low-density lipoprotein cholesterol.¹ These results align with prior evidence that the DASH diet can beneficially affect blood pressure measurements and cholesterol values. However, it is important to note that improvements in these risk factors did not translate into fewer cardiovascular events within the time frames studied.