Introduction

In the last 50 years in the United States, clinicians have seen a rise in diseases, including hypertension, diabetes, obesity, and coronary artery disease. An estimated 2000 people die of heart disease every day in the United States. Around 30% of US adults are hypertensive.[1] The risk factors of hypertension, fortunately, can be controlled to an extent by utilizing the DASH diet. Chronic diseases related to diet and obesity have become significant causes of death in the United States across all ethnicities. Obesity has been linked to significant etiological factors in diabetes, hypertension, cancer, and coronary artery disease.

Although there have been several advancements in the scientific world regarding new medications and cutting-edge diagnostic techniques, the rate of these diseases has multiplied many times. This increase has been steep, particularly in the last 20 years. Due to this trend, major organizations, including the American Heart Association, National Institutes of Health, and National Heart, Lung, and Blood Institute, have all started looking at an integrative approach to managing this growing epidemic. Diagnostic testing and medications are still the mainstays of patient management. However, the importance of diet, exercise, stress reduction, and lifestyle habits cannot be ignored.[2][3][4]

Function

A typical modern North American diet is high in saturated fats, omega-6 fatty acids, high glycemic load carbohydrates, and many artificial additives. This unhealthy diet, combined with little training in nutrition among medical professionals, is considered a significant setback in tackling these diseases. Fortunately, tremendous research has been done in the last few decades examining the effects of dietary patterns on chronic diseases. This information is easily available to physicians online.[5][6][7]

The Dietary Approaches to Stop Hypertension (DASH) diet originated in the 1990s. In 1992, the National Institute of Health (NIH) started funding several research projects to see if specific dietary interventions were useful in treating hypertension. Subjects in the study were advised to follow the dietary interventions and not include any other lifestyle modifications to avoid confounding factors. They found that only the dietary intervention alone could decrease systolic blood pressure by about 6 to 11 mm Hg. This effect was seen both in hypertensive and normotensive people. Based on these results, in some instances, DASH has been advocated as the first-line pharmacologic therapy along with lifestyle modification.

The DASH promotes the consumption of vegetables and fruits, lean meat and dairy products, and the inclusion of micronutrients in the menu. It also advocates the reduction of sodium in the diet to about 1500 mg/day. DASH emphasizes the consumption of minimally processed and fresh food. The DASH diet has many similarities to other dietary patterns promoted for cardiovascular health. The DASH diet is a culmination of the ancient and modern world. Scientists have derived it based on certain ancient nutritional principles, and it has been tailored to target some of the leading killers of contemporary society.

A typical serving guide for a patient following the DASH diet is as follows:

1. Vegetables: about 5 servings per day
2. Fruits: about 5 meals per day 
3. Carbohydrates: about 7 servings per day
4. Low-fat dairy products: about 2 servings per day
5. Lean meat products: about 2 or fewer servings per day
6. Nuts and seeds: 2 to 3 times per week

Following is a closer look at these recommendations.

Carbohydrates

Carbohydrates in the diet are mainly composed of cellulose and starches. The human body cannot digest cellulose, which is mainly present in plant fiber. Healthy starches or “carbs” have to be included in the diet, not just for the energy supply but also for the protective micronutrients. Low-carb diets are not as healthy as they may lead to decreased caloric intake than recommended or consumption of unhealthy fats as a substitute.

Healthy carbohydrates included under DASH include:

• Green leafy vegetables: kale, broccoli, spinach, collards, mustards
• Whole grains: cracked wheat, millet, oats
• Low glycemic index fruits
• Legumes and beans

Fats

Fats have been a prime suspect for some time now in the development of the chronic disease epidemic. However, research has now shown otherwise. Fats are now classified as good fats and bad fats. Good fats prevent inflammation, provide essential fatty acids, and promote overall health. When consumed in moderation, these fats have been shown to increase HDL and lower small, dense LDL particles. Some of the sources of good fats also included in DASH include:

• Olive oil
• Avocados
• Nuts
• Hempseeds
• Flax seeds
• Fish rich in omega-3 fatty acids

Bad fats, such as margarine, vegetable shortenings, and partially hydrogenated vegetable oils, increase small LDL particles, which promote atherogenesis. Fats are a highly condensed source of energy and, therefore, must be consumed in moderation. The serving sizes for fats are much smaller than those for other nutrients on the DASH recommendations.

Proteins 

The DASH recommends more servings of plant proteins like legumes, soy products, nuts, and seeds. Animal protein should mainly be composed of lean meats, low-fat dairy, eggs, and fish. Processed and cured meats are not recommended as they have been shown to cause hypertension and also contain carcinogens. The DASH diet also includes foods rich in potassium, calcium, and magnesium, as these prevent endothelial dysfunction and promote endothelial smooth muscle relaxation. Some foods rich in potassium include bananas, oranges, and spinach. Calcium is rich in dairy products and green leafy vegetables. Magnesium is present in various whole grains, leafy vegetables, nuts, and seeds.[8][9]

Clinical Significance

Is the DASH diet exclusively preferred only for treating HTN?

Since the formulation of the DASH diet pattern, it has been studied extensively to look for its effects on multiple other diseases. Several studies have shown that the DASH diet helps lower blood glucose levels, triglycerides, LDL-C, and insulin resistance. This makes the DASH diet an essential adjunct to pharmacological therapy in metabolic syndromes, a major epidemic in this country. It also has been a successful tool in weight management. In certain populations, adherence to the DASH diet has significantly improved control of type 2 diabetes. It is a preferred diet in patients with heart failure due to its emphasis on reducing dietary sodium and encouraging the intake of potassium, magnesium, and calcium.

The DASH diet has also shown a reduction in the incidence of colorectal cancer, mainly in the white population. The DASH diet has also been proven helpful to some extent in chronic liver disease, diverticular disease, and celiac disease.[10] The DASH diet has also been demonstrated in multiple studies to have lowered all-cause mortality in adults.[11] The DASH diet can be pertinent to preventing chronic heart failure and its management. Prospective observational studies have shown that a diet consistent with DASH eating patterns has lower rates of incidence of heart failure in women and decreases the prevalence of hospitalization from heart failure and death in men.[12]

The DASH diet is an essential strategy for lowering blood pressure in patients with diabetes mellitus type 2. The American Diabetic Association recommends that patients with diabetes who are at risk should consume the US Department of Agriculture’s Dietary Reference Intake for fiber, whole grains, and macronutrients. Moreover, these patients should limit saturated fat to < 7% of total daily calories, reduce trans fat intake, reduce cholesterol to < 200 mg/day, and limit sugar-sweetened beverages. Because the DASH diet meets these recommendations, adherence in patients with diabetes mellitus should be advocated for adequate blood pressure control.[13] Based on these studies, it is safe to say that DASH can be a very useful tool for physicians to tackle these diseases more efficiently when combined with pharmacological intervention. Compared to other diet patterns, it has the added advantage of having clear guidelines on serving sizes and food groups, making it easier for physicians to prescribe and monitor their patient's improvement.[2][14]

Enhancing Healthcare Team Outcomes

The DASH diet is a nutritionally based approach to prevent and control hypertension. The diet has been tested in several clinical trials and has been shown to lower cholesterol, saturated fats, and blood pressure. The DASH diet has been recommended as the best diet to help people who want to lose weight, maintain a healthy weight, and lower their blood pressure. The key fact is that this diet needs to be promoted to patients. Besides clinicians, nurses and pharmacists play a key role in educating patients about the benefits of this diet. Before discharge, nurses are in a prime position to educate all patients and their families about the DASH diet and its benefits. Similarly, when patients visit a pharmacy, the pharmacist should educate the patient about the DASH diet. The most important feature of the DASH diet is that it requires a lifestyle change and adopting a healthy way of eating. In addition, patients should be urged to stop smoking, abstain from alcohol, and do some physical activity regularly.[15][16][17] The DASH diet should be implemented under the guidance of an interprofessional healthcare team that includes clinicians, mid-level practitioners, nurses, pharmacists, and dieticians. This drives optimal patient outcomes from using this diet.

Outcomes

The DASH diet has been well-studied in many clinical trials, most associated with lowering blood pressure. Further, there is evidence to show that the DASH diet also lowers the risk of adverse cardiac events, stroke, type 2 diabetes, and obesity. Unfortunately, compliance with the diet remains low. Outside of clinical trials, there are limited studies on the long-term effectiveness of the DASH diet.[18][19]