Biomarker Analysis Supports Heart Benefit of Plant-Based Diets – Physician’s Weekly

DASH diet or high fruit and vegetable diet equally beneficial

Regardless of health status, eating more fruits and vegetables — meaning 10 or more servings daily — can reduce subclinical damage to the heart, according to findings published in Annals of Internal Medicine.

Stephen P. Juraschek, MD, PhD of Beth Israel Deaconess Medical Center in Boston, and colleagues looked back at serology samples from the DASH study that sought to determine the effect of diet on blood pressure and cholesterol. The 8-week long DASH study compared three diets — a traditional American diet, a diet rich in fruits and vegetables, and the so-called DASH diet, which was heavy on fruits and vegetables but also low in fats — to determine the dietary impact on biomarkers of subclinical damage to the heart.

In this new analysis, they compared levels of highly sensitivity cardiac troponin I, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high-sensitivity c-reactive protein in blood samples collected at baseline in the DASH study and after the 8-week-long intervention. They analyzed specimens from 326 of the original 459 DASH trial participants.

The original DASH trial was conducted in the mid-1990s and, at that time, the mean age of the participants was “was 45.2 years, 48% were women, 49% were black, and mean baseline BP was 131/85 mmHg.”

In this analysis, both the fruit and vegetable diet and the DASH diet reduced troponin I concentrations and NT-proBNP levels, compared to the control diet. “But levels of hs-CRP did not differ among diets,” they wrote. “We believe these findings strengthen recommendations for the DASH diet and, more generally, for increased consumption of fruits and vegetables as a means of optimizing cardiovascular health.

“Compared with the control diet, the fruit-and-vegetable diet reduced hs-cTnI levels by 0.5 ng/L (95% CI, 0.9-0.2 ng/L) and NT-proBNP levels by 0.3 pg/mL (CI, 0.5-0.1 pg/mL). Compared with the control diet, the DASH diet reduced hs-cTnI levels by 0.5 ng/L (CI, 0.9-0.1 ng/L) and NT-proBNP levels by 0.3 pg/mL (CI, 0.5-0.04 pg/mL),” they found.

Juraschek and colleagues noted that the original study found the DASH diet lowered both systolic and diastolic blood pressure and reduced LDL-C more than the fruit and vegetable diet.

However, that benefit “did not translate into significant differences in hs-cTnI and NT-proBNP levels between the fruit-and-vegetable and DASH diets at 8 weeks,” they explained. “Although reductions in these markers reflect short-term improvements in subclinical CVD injury, their relationships with CVD events have been observed independent of pathways predicted by traditional risk factors. Thus, they do not necessarily capture, for example, long-term ischemic risk from atherosclerotic plaque burden and potential rupture. This distinction is important, because the BP- and cholesterol-reducing features of the DASH diet probably still play an important role in long-term CVD risk prevention. Further research is needed to study the longitudinal effects of the DASH diet on CVD events.”

In an editorial that accompanied the report by Juraschek et al, Ramon Estruch, MD, PhD, and Rosa Casas, MD, PhD, from the University of Barcelona, along with Emilio Ros, MD, PhD, Instituto de Salud Carlos III, Madrid, Spain, were enthusiastic in their praise of the findings, noting that the researchers took advantage of the original data set and stored serum specimens of the DASH clinical trial (4) and compared the effects of the 3 feeding interventions…”

Estuch, Casas, and Ros pointed out that highly sensitive troponin I “is useful for diagnosing minor myocardial injury in patients with clinical manifestations of atherosclerotic CVD and is an excellent predictor of heart failure hospitalization and cardiac death (5); NT-proBNP has emerged as a hallmark biomarker for the diagnosis and prognosis of heart failure… ” but hs-CRP—the inflammatory marker that was not affected by diet — “is a much debated nonspecific marker of systemic inflammation, for which inconsistent results have been found concerning its incremental value in CVD risk prediction.”

The researchers and the editorialists noted that the benefits of a diet rich in fruits and vegetables include “higher amounts of potassium, magnesium, and fiber,” benefits that may explain the observed effects.

“High intake of fruits and vegetables is the basis of a healthy diet, and almost all medical and nutrition societies, as well as governments, recommend eating these foods daily to reduce the risk for CVD and improve overall health. However, the recommendations vary, from up to 400 g/d (5 servings per day) in England to 640 to 800 g/d (around 8 to 10 servings per day) in the United States,” wrote Ramon Estruch, Casas, and Ros. “Likewise, a recent meta-analysis of 95 prospective studies concluded that for each 200-g/d (2.5 servings per day) increase in the intake of fruits, vegetables, or fruits and vegetables combined, coronary heart disease risk decreased 8% to 16%, stroke risk decreased 13% to 18%, CVD risk decreased 8% to 13%, and all-cause mortality risk decreased 10% to 15%. When consumption of fruits and vegetables was 800 g/d or greater (>10 servings per day), these risks were reduced by 24%, 33%, 38%, and 31%, respectively. The same meta-analysis found that the foods with the strongest beneficial associations with CVD and mortality were apples and pears, citrus fruits, green leafy vegetables, cruciferous vegetables, tomatoes, and fresh salads. In contrast, intake of canned fruits was associated with an increased risk for CVD and all-cause mortality.”

Among the study limitations listed by Juraschek and colleagues was the fact that they were not able to analyze samples from all DASH trial participants, thus the findings “are observational and susceptible to confounding.”

Also, they suggested that the freezing-thawing process used for the serum specimens may have degraded the utility of hs-CRP.

Finally, they noted that 8-weeks is a short study duration — to0 short to assess clinical events.

That said, the editorial writers offered a broad interpretation of the significance of the findings, suggesting that recommendations “to increase the intake of fruits and vegetables to at least 10 servings per day should be generalized to the overall population, regardless of health status.”

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