By Jeffrey H. Baker, MD, FAAFP, DABIHM, DABMA

Assistant Professor, Department of Family and Community Medicine, Penn State College of Medicine

Dr. Baker reports no financial relationships relevant to this field of study.

SYNOPSIS: In individuals without pre-existing cardiovascular disease, the Dietary Approaches to Stop Hypertension diet plan and a diet consisting of fruits and vegetables, given over eight weeks, lowered biomarkers for cardiac strain and injury.

SOURCE: Juraschek SP, Kovell LC, Appel LJ, et al. Associations between dietary patterns and subclinical cardiac injury. Ann Intern Med 2020;172:786-794.

Clinicians continue to search for ways to aid patients in long-term disease prevention, whether by primary or secondary actions. A primary focus is continuing to reduce cardiovascular disease (CVD) risk. Although many interventions exist, elevated blood pressure (BP) is a main factor influencing the development of CVD. Therefore, prevention and control are on the list of clinical concerns.1,2

Twenty-four years have passed since the Dietary Approaches to Stop Hypertension (DASH) study was published, showing that dietary interventions could lower systolic BP (SBP) and diastolic BP (DBP), as well as low-density lipoprotein (LDL) cholesterol.3 Using current testing profiles on historic and curated specimens reveals new information regarding the importance of this diet plan. Juraschek et al hypothesized dietary intervention would reduce cardiovascular injury and aid in primary prevention of CVD. They studied stored samples from a subpopulation of the original DASH trial participants to assess the effects of diet on three biomarkers of subclinical cardiac injury. They examined high-sensitivity troponin I (hs-cTnI) as a marker of cardiac myocyte damage, N-terminal pro-B-type natriuretic peptide (NT-proBNP) as a marker of cardiac strain, and high-sensitivity C-reactive protein (hs-CRP) as a marker for inflammation. These three markers have been shown to predict risk for vascular events in adults without known CVD.4-6 The authors of the DASH trial, conducted between September 1994 and March 1996, compared the influence of three isocaloric dietary styles (plans) on SBP.3 The plans used were:

  • a control, typical of American consumption at that time;
  • a “fruit and vegetable” diet;
  • the DASH diet, supported by the American Heart Association for “managing blood pressure and reducing risk of heart attack, stroke, and other blood pressure-related health threats.”7,8

Four clinical research centers were involved, selecting 459 participants and randomly assigning them to one of three iso-caloric, prepared dietary plans following a three-week run-in period of the control plan. The control dietary plan consisted of a fiber and macronutrient content of average consumption, with potassium, magnesium, and calcium levels close to the 25th percentile of U.S. consumption. The fruit and vegetable diet plan contained higher quantities of fiber, potassium, and magnesium levels, close to the 75th percentile of human consumption.

The combination DASH diet contained the same higher levels of calcium, potassium, and magnesium, but also included low-fat dairy foods and lower amounts of saturated fat, total fat, and cholesterol compared to the control.

All three plans limited salt to 3 g per day to reduce sodium’s potential effects on SBP. The trial duration for participants was eight weeks. The original study revealed the DASH diet could significantly lower SBP, DBP, and LDL cholesterol.3

Juraschek et al used blood samples curated by the National Heart, Lung, and Blood Institute Biologic Specimen and Data Repository Information Coordinating Center (BioLINCC) from three of the four original sites submitting samples in the DASH trial, totaling 326 of the 459 trial participants. Of these 326 participants, 108 were assigned to the control plan, 109 to the fruit and vegetable plan, and 109 to the DASH diet plan.

The three markers of cardiac injury were analyzed from the baseline and eight-week samples. As in the original trial, the mean age of participants was 45.2 years. Of the participants, 52% were men, 48% were women, and 49% were Black.

Exclusions for the original DASH trial (and this analysis) included adults with diabetes mellitus, those taking antihypertensive medications, a body mass index greater than 35 kg/m2, renal insufficiency, or self-reported alcoholic beverage intake of greater than 14 drinks per week. Statistically significant changes in values of hs-cTnI and NT-proBNP from baseline to eight weeks were seen in both the DASH and fruit and vegetable diet, but not in hs-CRP levels.

Compared with the control diet, the DASH plan reduced hs-cTnI levels by 0.5 ng/L (95% confidence interval [CI], -0.9 to 0.1 ng/L) and NT-proBNP levels by 0.3 pg/mL (95% CI, -0.5 to -0.04 pg/mL), while the fruit and vegetable plan lowered hs-cTnI levels by 0.5 ng/L (95% CI, -0.9 to -0.2 ng/L) and NT-proBNP levels by 0.3 pg/mL (95% CI, -0.5 to -0.1 pg/mL). There were no differences noted among the plans regarding hs-CRP.

The authors acknowledged both the DASH and the fruit and vegetable plans lowered markers equally for myocyte damage and strain during the eight-week period. They suggested these plans were higher in fiber, magnesium, and potassium, leading to the effects, but noted further research is needed to confirm these findings. The authors observed patient weight is a principal determinant of elevated hs-CRP levels in obese adults, because this dietary intervention did not result in weight reduction, unlike other studies that showed reduction in hs-CRP with weight loss.

Juraschek et al conceded several limitations to their study analysis. Not all specimens were available from the DASH trial, and the findings were only observational in association with the injury markers, not to effects on clinical outcomes. The study lasted only eight weeks, again, without effect on clinical outcomes. There was concern over the freeze-thaw of samples, causing drift in the test levels, especially hs-CRP.

However, the authors argued their study showed strengths in the original control and administration of diet plans and the use of individuals without CVD. The diets were calorie-controlled, minimizing weight change factors on the markers. Therefore, the recent demonstration of changes in markers of cardiac injury and strain imply that in even the short term of eight weeks, the effect on future CVD events can occur from dietary interventions.

COMMENTARY

DASH established the importance of aiding BP reduction by increasing the amount of fresh fruits and vegetables in the diet and reducing saturated fats, thereby increasing magnesium and potassium. The work by Juraschek et al alerted clinicians to techniques to reduce pre-event markers for cardiovascular damage and perhaps the events that change lives. There may be no new tests to order for reassurance or concern, but there is more meaningful knowledge and conceptual information to pass on to patients to help them be healthy. The concepts, research, plans, and guides for the DASH dietary plan are readily available in books and online as technology apps and classes.

The scientific evidence supports the DASH diet in helping control many aspects of heart disease, and even all-cause mortality.9 In the recent report of the White House Conference on Food, Nutrition, and Health, listed in the number of priority executive recommendations, was, “Equip health professionals with effective nutrition interventions and better nutrition knowledge.”10 Many medical specialty colleges and academic groups support good nutrition to prevent chronic diseases. Nutrition is one of the six pillars of the American College of Lifestyle Medicine in supporting the prevention and treatment of chronic diseases, including CVD.

Analyzing NHANES data collected between 2007 and 2012 and comparing intake of nine nutrients to target amounts, Kim and Andrade found hypertensive patients scored poorly (2.6 out of a possible 9 score in accordance to DASH targets), and that the reported diet was associated with increased consumption of sodium, saturated fat, total fat, and protein.11

Certainly, financial hurdles and regular access to fresh foods in rural or urban areas described as “food deserts” are becoming more apparent. Consuming fresh vegetables and fruit, as well as lean and grass-fed, free-range meats, is an expensive change. But the diet can be adopted in low-income communities at reasonable cost.12,13

The DASH plan has not been sold as a “quick fix” for the upcoming wedding or prom, but as a lifelong lifestyle approach to good health. It is not an eating style that is as fast or convenient as the population generally desires. It takes time, commitment, and discipline for individual change to occur.

Steinberg et al, in a viewpoint statement, addressed the economic hurdles and those of the clinician in providing counseling support for their hypertensive patients. They noted clinicians often are too busy to tackle the details of lifestyle nutrition in a short office visit, advocating for sodium reduction at a minimum and referring patients to registered dieticians who are suited for dietary counseling. Although the emergence of self-management health tools for cellphones are a unique opportunity to help educate, the authors argued a limited number of tools truly are evidence-based.14

Twenty-four years after the original study, the DASH diet plan continues to resonate as a clinician’s tool in facilitating CVD risk reduction. Considering the evidence accumulated, it is an easy recommendation to make to all patients at risk for hypertension as well as those already working to reduce their hypertensive burden. Juraschek et al provided further data to support that dietary lifestyle adherence potentially reduces preclinical damage and CVD risk. Using this information to support patients’ individual efforts to improve or maintain their health status will be well worth the time and effort in doing so.

REFERENCES

  1. Fuchs FD, Whelton PK. High blood pressure and cardiovascular disease. Hypertension 2020;75:285-292.
  2. Bundy JD, Li C, Stuchlik P, et al. Systolic blood pressure reduction and risk of cardiovascular disease and mortality: A systematic review and network meta-analysis. JAMA Cardiol 2017;2:775-781.
  3. Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. N Engl J Med 1997;336:1117-1124.
  4. Jia X, Sun W, Hoogeveen RC, et al. High-sensitivity troponin I and incident coronary events, stroke, heart failure hospitalization, and mortality in the ARIC study. Circulation 2019;139:2642-2653.
  5. Everett BM, Berger JS, Manson JE, et al. B-type natriuretic peptides improve cardiovascular disease risk prediction in a cohort of women. J Am Coll Cardiol 2014;64:1789-1797.
  6. Parrinello CM, Lutsey PL, Ballantyne CM, et al. Six-year change in high-sensitivity C-reactive protein and risk of diabetes, cardiovascular disease, and mortality. Am Heart J 2015;170:380-389.
  7. Van Horn L, Carson JAS, Appel LJ, et al. Recommended dietary pattern to achieve adherence to the American Heart Association/American College of Cardiology guidelines: A scientific statement from the American Heart Association. Circulation 2016;134:e505-e529.
  8. American Heart Association. Managing blood pressure with a heart-healthy diet. Updated Oct. 31, 2016.
  9. Soltani S, Arablou T, Jayedi A, Salehi-Abargouei A. Adherence to the Dietary Approaches to Stop Hypertension (DASH) diet in relation to all-cause and cause-specific mortality: A systematic review and dose-response meta-analysis of prospective cohort studies. Nutr J 2020;19:37.
  10. Mande J, Willett W, Auerbach J, et al. Report of the 50th anniversary of the White House Conference on Food, Nutrition, and Health: Honoring the past, taking actions for our future. Boston, MA; March 2020.
  11. Kim H, Andrade FCD. Diagnostic status of hypertension on the adherence to the Dietary Approaches to Stop Hypertension (DASH) diet. Prev Med Rep 2016;4:525-531.
  12. Young CM, Batch BC, Svetkey LP. Effect of socioeconomic status on food availability and cost of the Dietary Approaches to Stop Hypertension (DASH) dietary pattern. J Clin Hypertens (Greenwich) 2008;10:603-611.
  13. Beydoun MA, Nkodo A, Fanelli-Kuczmarski MT, et al. Longitudinal associations between monetary value of the diet, DASH diet score and the allostatic load among middle-aged urban adults. Nutrients 2019;11:2360.
  14. Steinberg D, Bennett GG, Svetkey L. The DASH diet, 20 years later. JAMA 2017;317:1529-1530.