DASH diet


The Dietary Approaches to Stop Hypertension 'diet' is a diet to control hypertension promoted by the U.S.-based National Heart, Lung, and Blood Institute, part of the National Institutes of Health, an agency of the United States Department of Health and Human Services. The DASH diet is rich in fruits, vegetables, whole grains, and low-fat dairy foods. It includes meat, fish, poultry, nuts, and beans, and is limited in sugar-sweetened foods and beverages, red meat, and added fats. In addition to its effect on blood pressure, it is designed to be a well-balanced approach to eating for the general public. DASH is recommended by the United States Department of Agriculture as a healthy eating plan. The DASH diet is one of three healthy diets recommended in the 2015–20 U.S. Dietary Guidelines, which also include the Mediterranean diet and a vegetarian diet. The American Heart Association  considers the DASH diet "specific and well-documented across age, sex and ethnically diverse groups."
The DASH diet is based on NIH studies that examined three dietary plans and their results. None of the plans were vegetarian, but the DASH plan incorporated more fruits and vegetables, low fat or non-fat dairy, beans, and nuts than the others studied. The DASH diet reduced systolic blood pressure by 6 mm Hg and diastolic blood pressure by 3 mm Hg in patients with high normal blood pressure. Those with hypertension dropped by 11 and 6 mm Hg, respectively. These changes in blood pressure occurred with no changes in body weight. The DASH dietary pattern is adjusted based on daily caloric intake ranging from 1,600 to 3,100 dietary calories. Although this diet is associated with a reduction of blood pressure and improvement of gout, there are uncertainties around whether its recommendation of low-fat dairy products is beneficial or detrimental. The diet is also advised to diabetic or obese individuals.
The DASH diet was further tested and developed in the Optimal Macronutrient Intake Trial for Heart Health. "The DASH and DASH-sodium trials demonstrated that a carbohydrate-rich diet that emphasizes fruits, vegetables, and low-fat dairy products and that is reduced in saturated fat, total fat, and cholesterol substantially lowered blood pressure and low-density lipoprotein cholesterol. OmniHeart demonstrated that partial replacement of carbohydrate with either protein or with unsaturated fat can further reduce blood pressure, low-density lipoprotein cholesterol, and coronary heart disease risk."
In January 2018, DASH was named the number one for "Best Diets Overall" for the eighth year in a row, and also as "For Healthy Eating", and "Best Heart-Healthy Diet"; and tied number two "For Diabetes" in the U.S. News & World Reports annual "Best Diets" rankings.
The DASH diet is similar to the Mediterranean diet and the AHA diet, and has been one of the main sources for the MIND diet recommendations.

Description

The DASH diet is mainly based on fruits, vegetables, low-fat or fat free dairy, whole grains, fish, poultry, legumes, and nuts. It recommends reducing sodium intake, sweets, and red meat. It limits saturated fat and trans fat, while increasing the intake of potassium, magnesium, protein, fiber, and nutrients thought to help control blood pressure.
The National Heart, Lung, and Blood Institute provides sample plans with specific number of servings based on 1600, 2000 or 2600 calories per day. Here is the sample plan for 2000 calories daily:
  • 6–8 servings of grains or grain products
  • 4–5 servings of fruits
  • 4–5 servings of vegetables
  • 2–3 servings of low-fat dairy foods
  • 2–3 servings of fats and oils
  • 2 or fewer servings of meat, poultry or fish
With the following weekly limitations:
  • 4–5 servings of nuts, seeds or dry beans
  • sweets, desserts, food with added sugars limited to a maximum of 5 servings
Following this diet requires some planning and cooking. To ease this, both the NHLBI and NIH maintain lists of healthy recipes.
There is some conflicting data about the need for low-fat dairy foods, with some studies showing beneficial effects while others detrimental effects.
Elements can be replaced by alternatives for those with allergies or lactose intolerance, such as lactose-free products instead of dairy, and seeds instead of nuts. There is some evidence that replacing animal proteins with plant-based proteins, such as nuts and seeds, reduces mortality risks.
Some people may at first experience gas and bloating due to the high fiber content of plant foods such as fruits, vegetables and whole grains. This can be partially alleviated by limiting high fiber foods intake to 1 or 2 per week initially and progressively increasing. This may also be alleviated by substituting high-protein sources of fiber, like beans, with high-carbohydrate sources of fiber, like whole grains.
DASH in addition with a reduction of sodium intake is associated with a reduction of blood pressure, in both individuals with and without hypertension.

Health effects

Cardiovascular disease and hypertension

The first modifications recommended by guidelines for people at risk of cardiovascular disease are typically lifestyle changes, such as diet and physical activity followed by pharmacotherapy. A diet that consists of high sodium, sugar-sweetened beverages, red meat and processed red meat consumption have been associated with cardiovascular death. The DASH diet along with similar diets like the Mediterranean diet that are rich in vegetables and fruit and low in saturated fats and trans fats are encouraged by multiple cardiovascular guidelines including the American Heart Association and American College of Cardiology, Canadian Cardiovascular Society, and 2016 European Guidelines.
Hypertension is a cardiovascular disease risk factor and blood pressure has been used as a surrogate marker for cardiovascular disease benefits. The DASH diet is seen in many guidelines for hypertension; which is typically defined as having a blood pressure greater than 140/90 mmHg with some guidelines defining it as having a blood pressure greater than 130/90 mmHg.
In a systematic review, the DASH diet reduced blood pressure by an average of 5.2/2.6 mmHg, however the blood pressure lowering effects may vary and will typically have a greater effect in people with a higher baseline blood pressure or BMI. The review found the DASH diet to reduce total cholesterol concentrations by 0.20 mmol/L. Using the average values for reductions in cholesterol levels and BP, the review concluded that the DASH diet was found to reduce the 10-year Framingham risk score for cardiovascular disease by about 13%.

History and design

Background

Currently, hypertension is thought to affect roughly 50 million people in the U.S. and approximately 1 billion worldwide. According to the National Heart, Lung and Blood Institute, citing data from 2002, "The relationship between BP and risk of cardiovascular disease events is continuous, consistent, and independent of other risk factors. The higher the BP, the greater is the chance of heart attack, heart failure, stroke, and kidney disease. For individuals 40–70 years of age, each increment of 20 mm Hg in systolic BP or 10 mm Hg in diastolic BP doubles the risk of CVD across the entire BP range from 115/75 to 185/115 mm Hg.".
The prevalence of hypertension led the U.S. National Institutes of Health to propose funding to further research the role of dietary patterns on blood pressure. In 1992 the NHLBI worked with five of the most well-respected medical research centers in different cities across the U.S. to conduct the largest and most detailed research study to date. The DASH study used a rigorous design called a randomized controlled trial, and it involved teams of physicians, nurses, nutritionists, statisticians, and research coordinators working in a cooperative venture in which participants were selected and studied in each of these five research facilities. The chosen facilities and locales for this multi-center study were: Johns Hopkins University in Baltimore, Maryland, Duke University Medical Center in Durham, North Carolina, Kaiser Permanente Center for Health Research in Portland, Oregon, Brigham and Women's Hospital in Boston, Massachusetts, and Pennington Biomedical Research Center in Baton Rouge, Louisiana.
Two DASH trials were designed and carried out as multi-center, randomized, outpatient feeding studies with the purpose of testing the effects of dietary patterns on blood pressure. The standardized multi-center protocol is an approach used in many large-scale multi-center studies funded by the NHLBI. A unique feature of the DASH diet was that the foods and menu were chosen based on conventionally consumed food items so it could be more easily adopted by the general public if results were positive. The initial DASH study was begun in August 1993 and ended in July 1997. Contemporary epidemiological research had concluded that dietary patterns with high intakes of certain minerals and fiber were associated with low blood pressures. The nutritional conceptualization of the DASH meal plans was based in part on this research.

Diet

Two experimental diets were selected for the DASH study and compared with each other, and with a third: the control diet. The control diet was low in potassium, calcium, magnesium and fiber and featured a fat and protein profile so that the pattern was consistent with a "typical American diet at the time". The first experimental diet was higher in fruits and vegetables but otherwise similar to the control diet, with the exception of fewer snacks and sweets. Magnesium and potassium levels were close to the 75th percentile of U.S. consumption in the fruits-and-vegetables diet, which also featured a high-fiber profile. The second experimental diet was high in fruits and vegetables and in low-fat dairy products, as well as lower in overall fat and saturated fat, with higher fiber and higher protein compared with the control diet—this diet has been called "the DASH diet". The DASH diet was rich in potassium, magnesium and calcium—a nutrient profile roughly equivalent with the 75th percentile of U.S. consumption. The combination or "DASH" diet was also high in whole grains, poultry, fish, and nuts while being lower in red meat content, sweets, and sugar-containing beverages.
The DASH diet was designed to provide liberal amounts of key nutrients thought to play a part in lowering blood pressure, based on past epidemiologic studies. One of the unique features of the DASH study was that dietary patterns rather than single nutrients were being tested. The DASH diet also features a high quotient of antioxidant-rich foods thought by some to retard or prevent chronic health problems, including cancer, heart disease, and stroke.
Researchers have also found that the DASH diet is more effective than a low-oxalate diet in the prevention and treatment of kidney stones, specifically calcium oxalate kidney stones.