The Dietary Approaches to Stop Hypertension (DASH) diet is recognized as an effective dietary intervention to reduce blood pressure. The blood pressure-lowering effect of the DASH diet was first noted more than 20 years ago, when the first DASH clinical trial, which was a controlled feeding trial, tested the effects of 3 different diets on blood pressure levels.

    The original DASH study (1) enrolled 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80 to 95 mm Hg. For three weeks, the subjects were fed a control diet that was low in fruits, vegetables, and dairy products, with a fat content typical of the average diet in the United States. The study participants were then randomly assigned to receive for eight weeks the control diet, a diet rich in fruits and vegetables, or a "combination" diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat. Sodium intake and body weight were maintained at constant levels.

    At baseline, the mean (±SD) systolic and diastolic blood pressures were 131.3±10.8 mm Hg and 84.7±4.7 mm Hg, respectively. The combination diet reduced systolic and diastolic blood pressure by 5.5 and 3.0 mm Hg more, respectively, than the control diet (p <0.001 for each); the fruits-and-vegetables diet reduced systolic blood pressure by 2.8 mm Hg more (p <0.001) and diastolic blood pressure by 1.1 mm Hg more (p = 0.07) than the control diet. Among the 133 subjects with hypertension (systolic pressure, >140 mm Hg; diastolic pressure, >90 mm Hg; or both), the combination diet reduced systolic and diastolic blood pressure by 11.4 and 5.5 mm Hg more, respectively, than the control diet (p <0.001 for each); among the 326 subjects without hypertension, the corresponding reductions were 3.5 mm Hg (p <0.001) and 2.1 mm Hg (p = 0.003).

    This study demonstrated that a diet rich in fruits, vegetables, and low-fat dairy foods and with reduced saturated and total fat can substantially lower blood pressure. This diet offers a nutritional approach to preventing and treating hypertension. Since then, many clinical trials have suggested that the DASH diet alone or in combination with other lifestyle changes, such as sodium restriction, weight loss, or physical exercise, is effective for blood pressure reduction across a wide range of blood pressure levels.

    A meta-analysis (2) assessed the DASH diet effect on blood pressure in adults with and without hypertension from 30 randomized clinical studies (n = 5545 participants, 45% men, mean age 51 years, mean BMI 29.2 kg/m2, mean baseline systolic blood pressure /diastolic blood pressure 134.3/84.9 mm Hg, mean follow-up period 15.3 week).

    Compared with a control diet, the DASH diet reduced both systolic blood pressure and diastolic blood pressure (difference in means: −3.2 mm Hg; 95% CI: −4.2, −2.3 mm Hg; p < 0.001, and −2.5 mm Hg; 95% CI: −3.5, −1.5 mm Hg; p <0.001, respectively). Hypertension status did not modify the effect on blood pressure reduction. The DASH diet compared with a control diet reduced systolic blood pressure levels to a higher extent in trials with sodium intake >2.4 g/day than in trials with sodium intake ≤ 2.4 g/day, whereas both systolic blood pressure and diastolic blood pressure were reduced more in trials with mean age <50 y than in trials of older participants.

 

    This analysis confirmed that the adoption of the DASH diet results in significant systolic blood pressure and diastolic blood pressure reduction and that this effect is independent of baseline blood pressure levels. Although no differential blood pressure effect was noticed between hypertensive and nonhypertensive patients, the extent of systolic blood pressure and diastolic blood pressure reduction was higher by absolute means in hypertensive patients without underlying antihypertensive treatment than that observed in all hypertensive patients (2).

 

    Cardiovascular diseases are the leading cause of death globally. An estimated 17.9 million people died from cardiovascular diseases in 2019, representing 32% of all global deaths. Of these deaths, 85% were due to heart attack and stroke (from WHO fact sheet). Raised blood pressure is the leading risk factor for cardiovascular diseases. The recent Global Burden of Disease Study showed that high blood pressure accounted for 10.4 million deaths and 218 million disability-adjusted life years in 2017, and excess salt intake—a well-established cause of high blood pressure—was responsible for 3.2 million deaths and 70 million disability-adjusted life years (3).

 

    In 2013, the WHO recommended that all member states aim to reduce population salt intake by 30% by 2025. A review aims to identify all national salt reduction initiatives around the world was conducted in 2019 at the midpoint to quantify countries' progress in achieving the salt reduction target (3).

 

    A total of 96 national salt reduction initiatives were identified, representing a 28% increase in the number reported in 2014. About 90% of the initiatives were multifaceted in approach, and 60% had a regulatory component. Approaches include interventions in settings (n= 74, such as school programs), food reformulation (n= 68), consumer education (n= 50), front-of-pack labeling (n = 48), and salt taxation (n = 5). Since 2014, there has been an increase in the number of countries implementing each of the approaches, except consumer education.

 

    3 countries reported a substantial decrease (>2 g/day), 9 that reported a moderate decrease (1–2 g/day), and 5 that reported a slight decrease (<1 g/day) in the mean salt intake over time, but none of the countries have yet met the targeted 30% relative reduction in salt intake from baseline. Among the results from various countries, studies in China showed a 23% reduction of salt intake from 11.8 to 9.1 g between 2000 and 2009; studies in the United States showed only a 2% reduction from 8.7 g to 8.5 g between 2011 and 2016. There has been an increase in the number of salt reduction initiatives around the world since 2014. More countries are now opting for structural or regulatory approaches. However, efforts must be urgently accelerated and replicated in other countries and more rigorous monitoring and evaluation of strategies is needed to achieve the salt reduction target (3).

 

    DASH diet has been known for more than 20 years as an effective blood pressure-reducing dietary solution. World Health Organization has recognized the importance of reducing salt intake for health, especially preventing premature death from cardiovascular disease, and urged countries to implement policies accordingly.

 

    Nutrition education is a resource and time-intensive approach to help people learning healthy lifestyles and eating healthy foods. While the governments may not continue the educational efforts to the public due to the cost, we hope that you can think about adopting this nutrition strategy to help reduce hypertension and the risk of cardiovascular disease in your life since you have read this blog.

 

Reference List:

1. L J Appel, T J Moore, E Obarzanek, W M Vollmer, L P Svetkey, F M Sacks, G A Bray, T M Vogt, J A Cutler, M M Windhauser, P H Lin, N Karanja. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. N Engl J Med. 1997;336(16):1117-24. doi: 10.1056/NEJM199704173361601.

2. C D Filippou, C P Tsioufis, C G Thomopoulos, C C Mihas, K S Dimitriadis, L I Sotiropoulou , C A Chrysochoou, P I Nihoyannopoulos, D M Tousoulis. Dietary Approaches to Stop Hypertension (DASH) Diet and Blood Pressure Reduction in Adults with and without Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Adv Nutr. 2020;11(5):1150-1160.

3. J A Santos, D Tekle, E Rosewarne, N Flexner, L Cobb, A Al-Jawaldeh, W J Kim, J Breda, S Whiting, N Campbell et al. A Systematic Review of Salt Reduction Initiatives Around the World: A Midterm Evaluation of Progress Towards the 2025 Global Non-Communicable Diseases Salt Reduction Target. Adv Nutr 2021;12:1768–1780.