1. In this observational study derived from the DASH feeding trial, both diets that were rich in fruits and vegetables were found to be associated with lower levels of biomarkers indicative of cardiac damage and strain.
2. These findings add to the body of evidence supporting existing dietary guidelines.
Evidence Rating Level: 2 (Good)
Study Rundown: Cardiovascular disease (CVD) is the leading cause of death worldwide, and risk factors that have been identified include hypertension, diabetes, lack of physical activity, excessive alcohol consumption, and a poor diet, among others. While observational studies have linked a healthy diet with a reduced risk for CVD injury, very few studies have attempted to establish direct causality. The Dietary Approaches to Stop Hypertension (DASH) trial was a randomized feeding study that investigated the effects of 3 different diets on blood pressure and low-density lipoprotein cholesterol levels in middle-aged adults without known preexisting CVD. In this observational study that utilized stored specimens from the DASH trial, it was found that the two diets rich in fruits and vegetables were associated with lower subclinical cardiac damage and cardiac strain. However, inflammation did not vary significantly between groups. These findings strengthen current dietary guidelines aimed at maintaining cardiovascular health, but it remains unclear whether these dietary features are beneficial in those with established heart failure. Strengths of this study include the analysis of highly sensitive biomarkers and the use of isocaloric diets to minimize the confounding effect of weight change. The study was limited by a short follow-up period, missing data from over 30% of the original study population, and the inability to isolate the physiological effects of specific food groups or micronutrients.
Relevant Reading: A Clinical Trial of the Effects of Dietary Patterns on Blood Pressure
In-Depth [retrospective cohort]: In this study, specimens belonging to 326 of the 459 original DASH trial participants were examined for 3 biomarkers corresponding to cardiac damage, strain, and inflammation: high-sensitivity troponin I (hs-cTnI), N-terminal pro–B-type natriuretic peptide (NTproBNP), and high-sensitivity C-reactive protein (hs-CRP), respectively. Participants were fed 1 of 3 diets—a control diet that was low in fruits, vegetables, and dairy but high in fat; a “fruit and vegetable” diet that was also high in fat; or the DASH diet, which was high in fruits, vegetables, and dairy but low in fat—and tracked for 8 weeks. Weighted baseline characteristics were similar between groups despite the missing data. Decreases in hs-cTnI levels from baseline were observed in both the “fruit and vegetable” group (-0.9 ng/L [95% confidence interval (CI), -1.5 to -0.3 ng/L]) and the DASH group (-0.4 ng/L [95% CI, 0.6 to 0.2 ng/L]). Several participants in both groups had hs-cTnI levels that fell below the limit of detection of 1.6 ng/L. NT-proBNP levels also decreased in the “fruit and vegetable” group (-4.6 pg/mL [95% CI, -7.9 to -1.2 pg/mL]) as well as the DASH group (-4.0 pg/mL [95% CI, -7.3 to -0.8 pg/mL]). Compared with the control diet, the “fruit and vegetable” diet reduced hs-cTnI levels by 0.5 ng/L (95% CI, -0.9 to -0.2 ng/L) and NTproBNP levels by 0.3 pg/mL (95% CI, -0.5 to -0.1 pg/mL). Hs-CRP levels were similar between all groups, and the “fruit and vegetable” and DASH groups did not differ with respect to any of the three biomarkers.
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