Dietary Approaches to Stop Hypertension
Encyclopedia
The DASH diet is a diet
promoted by the National Heart, Lung, and Blood Institute
(part of the NIH, a United States government organization) to control hypertension
. This eating plan is rich in fruits, vegetables, whole grains, and low-fat dairy foods; 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 considered a well-balanced approach to eating for the general public. It is now recommended by the U.S. Department of Agriculture (USDA) as an ideal eating plan for all Americans.
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 nonfat dairy, beans, and nuts than the others studied. Not only does the plan emphasize good eating habits, but also suggests healthy alternatives to "junk food
" and discourages the consumption of processed foods. The NIH has published a guidebook, "Your Guide to Lowering your Blood Pressure With DASH", which details the nutrition facts of popular mainstream food items and their healthy alternatives. The manual also provides samples of meal plans and proportions along with their associated nutritional information. The last pages of the manual provides a list of resources and how to obtain them.
The diet reduced systolic blood pressure by 6 mm Hg
and diastolic blood pressure by 3 mm Hg in patients with normal blood pressure. Those with hypertension dropped by 11 and 6, respectively. There are several eating plans included in the diet, with the daily caloric intake ranging from 1699 to 3100 dietary calorie
s.
The prevalence of hypertension led the U.S. [National Institute of Health] (NIH) to propose funding to further research the role of key nutrients in the diet. In 1992 the NHLBI directed 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 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 the these five research facilities. The chosen facilities and locales for this multi-center study were (1) Johns Hopkins University
in Baltimore, Maryland, (2) Duke University Medical Center in Durham, North Carolina, (3) Kaiser Permanente
Center for Health Research in Portland, Oregon, (4) Brigham and Women's Hospital
in Boston, Massachusetts and (5) Pennington Biomedical Research Center
in Baton Rouge, Louisiana. [1].
The DASH trials were designed and carried out as a multi-center, randomized, outpatient feeding study with the purpose of testing the effects of dietary patterns on blood pressure. The standardized multi-center protocol was one of the unique features of the DASH diet. Another unique feature of the DASH diet and design was the foods and menu were chosen based on conventionally consumed food items which would be easily adopted by the general public if results were positive. [3]. The initial DASH study was begun in August 1993 and ended in July 1997. [2]. 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.[3]
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 characteristically low in potassium, calcium, magnesium and fiber. Moreover, the control diet also featured a fat and protein profile consistent with current or contemporary dietary regimens (a “typical American diet” [1]). The first experimental diet was an idealized “good” diet consisting of fruits and vegetables but otherwise similar to the control diet (a “fruits and vegetables diet” [2]), 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 combined elements of the previous two (control and fruits-and-vegetables)—this diet has been called “the DASH Diet” [5]. The Dash diet (or combination diet) was rich in potassium, magnesium and calcium—a nutrient profile roughly equivalent with the 75th percentile of U.S. consumption. The DASH diet was also high in fruits, vegetables & low fat dairy foods, and also rich in fiber and protein (18%). The combination or “DASH” diet was also high in whole grains, poultry, fish and nuts while being low in fat and red meat content, sweets and sugar-containing beverages [6].
The DASH diet was also focused on providing liberal amounts of key nutrients thought to play a part in lowering blood pressure, based on past medical studies. The DASH diet was designed to be a whole-food diet, low in processed or refined sugars and high in complex carbohydrates. [1]. One of the unique features of the DASH diet design is that dietary patterns rather than single nutrients were being tested. [3]. Equally important, the DASH diet features a high quotient of anti-oxidant rich foods thought to retard or prevent chronic health problems including cancer, heart disease and stroke. [1].
8,813 people were screened for the study, out of which were ultimately chosen 459 participants whose demographic characteristics most closely resembled the target population and study requirements. The sample population consisted of healthy men and women with an average age of 46, with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures within 80 to 95 mm Hg. African-American and other minority groups were planned to comprise 67% of the study sample, with 49% of the sample being female.[3]. Indeed, due to the exceptional burden of high blood pressure in minority populations, especially among African-Americans, a major goal of the trial was to recruit enough ethnic minorities to constitute two thirds of the target sample. [2].
Participants ate one of the three aforementioned dietary patterns in 3 separate phases of the trial, including (1) Screening, (2), Run-in and (3) Intervention. In the screening phase, participants were screened for eligibility based on the combined results of blood pressure readings and a Stanford 7-Day Physical Activity Recall questionnaire. In the 3 week run-in phase, each subject was given the control diet for 3 weeks, had their blood pressure measurements taken on each of five separate days, gave one 24-hour urine sample and completed a questionnaire on symptoms. At this point the subjects were each randomly assigned to one of the three diets outlined above, to begin at the start of the 4th week. The intervention phase followed next; this was an 8-week period in which the subjects followed the diet they had each been randomly assigned to. Blood pressures and urine samples were collected again during this time together with symptom & physical activity recall questionnaires. The first group of study subjects began the run-in phase of the trial in September 1994 while the fifth and final group began in January 1996. [2]. Each of the three diets contained the same 3 grams (3,000 mg) of sodium. Participants were also given two packets of salt, each containing 200 mg of sodium, for discretionary use. Alcohol was limited to no more than two beverages per day, and caffeine intake was limited to no more than three caffeinated beverages. [6].
, than when the starting level was higher (higher levels are the actual average in the U.S.). These results led researchers to postulate that the adoption of a national lower daily allowance for sodium than the currently held 2,400 mg could be based on the sound scientific results provided by this study. [7].
The DASH diet and the control diet at low salt levels were both successful in lowering blood pressure, but the largest reductions in blood pressure were obtained by eating a combination of these two (i.e., a low-salt version of the DASH diet). The effect of this combination at a sodium level of 1,500 mg/day was an average blood pressure reduction of 8.9/4.5 mm Hg (systolic/diastolic). The hypertensive subjects experienced an average reduction of 11.5/5.7 mm Hg. [6]. The DASH-sodium results indicate that low sodium levels correlated with the largest reductions in blood pressure for participants at both normative and hypertensive levels with the hypertensive participants showing the greatest reductions in blood pressure overall. Moreover, the African-American study participants showed particularly significant reductions in blood pressure.[1].
Dieting
Dieting is the practice of eating food in a regulated fashion to achieve or maintain a controlled weight. In most cases dieting is used in combination with physical exercise to lose weight in those who are overweight or obese. Some athletes, however, follow a diet to gain weight...
promoted by the National Heart, Lung, and Blood Institute
National Heart, Lung, and Blood Institute
The National Heart, Lung, and Blood Institute is a division of the National Institutes of Health, located in Bethesda, Maryland...
(part of the NIH, a United States government organization) to control hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
. This eating plan is rich in fruits, vegetables, whole grains, and low-fat dairy foods; 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 considered a well-balanced approach to eating for the general public. It is now recommended by the U.S. Department of Agriculture (USDA) as an ideal eating plan for all Americans.
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 nonfat dairy, beans, and nuts than the others studied. Not only does the plan emphasize good eating habits, but also suggests healthy alternatives to "junk food
Junk food
Junk food is an informal term applied to some foods that are perceived to have little or no nutritional value ; to products with nutritional value, but which also have ingredients considered unhealthy when regularly eaten; or to those considered unhealthy to consume at all...
" and discourages the consumption of processed foods. The NIH has published a guidebook, "Your Guide to Lowering your Blood Pressure With DASH", which details the nutrition facts of popular mainstream food items and their healthy alternatives. The manual also provides samples of meal plans and proportions along with their associated nutritional information. The last pages of the manual provides a list of resources and how to obtain them.
The diet reduced systolic blood pressure by 6 mm Hg
Torr
The torr is a non-SI unit of pressure with the ratio of 760 to 1 standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimetre of mercury, i.e., a pressure of 1 torr is approximately equal to 1 mmHg...
and diastolic blood pressure by 3 mm Hg in patients with normal blood pressure. Those with hypertension dropped by 11 and 6, respectively. There are several eating plans included in the diet, with the daily caloric intake ranging from 1699 to 3100 dietary calorie
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...
s.
History and Design
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 (NHLBI), citing data from 2002 , “The relationship between BP and risk of cardiovascular disease (CVD) 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 (SBP) or 10 mm Hg in diastolic BP (DBP) 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 Institute of Health] (NIH) to propose funding to further research the role of key nutrients in the diet. In 1992 the NHLBI directed 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 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 the these five research facilities. The chosen facilities and locales for this multi-center study were (1) Johns Hopkins University
Johns Hopkins University
The Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...
in Baltimore, Maryland, (2) Duke University Medical Center in Durham, North Carolina, (3) Kaiser Permanente
Kaiser Permanente
Kaiser Permanente is an integrated managed care consortium, based in Oakland, California, United States, founded in 1945 by industrialist Henry J. Kaiser and physician Sidney Garfield...
Center for Health Research in Portland, Oregon, (4) Brigham and Women's Hospital
Brigham and Women's Hospital
Brigham and Women's Hospital is the largest hospital of the Longwood Medical and Academic Area in Boston, Massachusetts. It is directly adjacent to Harvard Medical School of which it is the second largest teaching affiliate with 793 beds...
in Boston, Massachusetts and (5) Pennington Biomedical Research Center
Pennington Biomedical Research Center
The Pennington Biomedical Research Center, located in Baton Rouge, Louisiana, is a campus of the Louisiana State University System and conducts both clinical and basic research. According to its website, its mission is to promote healthier lives through research and education in nutrition and...
in Baton Rouge, Louisiana. [1].
The DASH trials were designed and carried out as a multi-center, randomized, outpatient feeding study with the purpose of testing the effects of dietary patterns on blood pressure. The standardized multi-center protocol was one of the unique features of the DASH diet. Another unique feature of the DASH diet and design was the foods and menu were chosen based on conventionally consumed food items which would be easily adopted by the general public if results were positive. [3]. The initial DASH study was begun in August 1993 and ended in July 1997. [2]. 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.[3]
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 characteristically low in potassium, calcium, magnesium and fiber. Moreover, the control diet also featured a fat and protein profile consistent with current or contemporary dietary regimens (a “typical American diet” [1]). The first experimental diet was an idealized “good” diet consisting of fruits and vegetables but otherwise similar to the control diet (a “fruits and vegetables diet” [2]), 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 combined elements of the previous two (control and fruits-and-vegetables)—this diet has been called “the DASH Diet” [5]. The Dash diet (or combination diet) was rich in potassium, magnesium and calcium—a nutrient profile roughly equivalent with the 75th percentile of U.S. consumption. The DASH diet was also high in fruits, vegetables & low fat dairy foods, and also rich in fiber and protein (18%). The combination or “DASH” diet was also high in whole grains, poultry, fish and nuts while being low in fat and red meat content, sweets and sugar-containing beverages [6].
The DASH diet was also focused on providing liberal amounts of key nutrients thought to play a part in lowering blood pressure, based on past medical studies. The DASH diet was designed to be a whole-food diet, low in processed or refined sugars and high in complex carbohydrates. [1]. One of the unique features of the DASH diet design is that dietary patterns rather than single nutrients were being tested. [3]. Equally important, the DASH diet features a high quotient of anti-oxidant rich foods thought to retard or prevent chronic health problems including cancer, heart disease and stroke. [1].
8,813 people were screened for the study, out of which were ultimately chosen 459 participants whose demographic characteristics most closely resembled the target population and study requirements. The sample population consisted of healthy men and women with an average age of 46, with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures within 80 to 95 mm Hg. African-American and other minority groups were planned to comprise 67% of the study sample, with 49% of the sample being female.[3]. Indeed, due to the exceptional burden of high blood pressure in minority populations, especially among African-Americans, a major goal of the trial was to recruit enough ethnic minorities to constitute two thirds of the target sample. [2].
Participants ate one of the three aforementioned dietary patterns in 3 separate phases of the trial, including (1) Screening, (2), Run-in and (3) Intervention. In the screening phase, participants were screened for eligibility based on the combined results of blood pressure readings and a Stanford 7-Day Physical Activity Recall questionnaire. In the 3 week run-in phase, each subject was given the control diet for 3 weeks, had their blood pressure measurements taken on each of five separate days, gave one 24-hour urine sample and completed a questionnaire on symptoms. At this point the subjects were each randomly assigned to one of the three diets outlined above, to begin at the start of the 4th week. The intervention phase followed next; this was an 8-week period in which the subjects followed the diet they had each been randomly assigned to. Blood pressures and urine samples were collected again during this time together with symptom & physical activity recall questionnaires. The first group of study subjects began the run-in phase of the trial in September 1994 while the fifth and final group began in January 1996. [2]. Each of the three diets contained the same 3 grams (3,000 mg) of sodium. Participants were also given two packets of salt, each containing 200 mg of sodium, for discretionary use. Alcohol was limited to no more than two beverages per day, and caffeine intake was limited to no more than three caffeinated beverages. [6].
Study Results
The DASH study showed that dietary patterns can and do affect blood pressure in the normal to moderately hypertensive adult population (systolic < 180 mm Hg & diastolic of 80 to 95 mm Hg). . Respectively, the DASH or “combination” diet lowered blood pressures by an average of 5.5 and 3.0 mm Hg for systolic and diastolic, compared to the control diet. The minority portion of the study sample and the hypertensive portion, from baseline, both showed the largest reductions in blood pressure from the combination diet against the control diet. The hypertensive subjects experienced a drop of 11.4 mm Hg in their systolic and 5.5 mm Hg in their diastolic phases. [2]. The fruits-and-vegetables diet was also successful, although it produced more modest reductions over the control diet (2.8 mm Hg systolic and 1.1 mm Hg diastolic) [6]. In the subjects with and without hypertension, the combination diet effectively reduced blood pressure more than the fruits-and-vegetables diet or the control diet did. The data indicated that reductions in blood pressure occurred within two weeks of subjects’ starting their designated diets, which were favorable results[6], and that the results were generalizable to the target sample of the U.S. population. [2]. Side effects were negligible, but the NEJM study reports that constipation was evidently a problem for some of the subjects. At the end of the intervention phase, 10.1, 5.4 & 4.0 percent of the subjects reported this problem for the control, fruits-and-vegetables and combination diets, respectively. Apart from only one subject (on the control diet) who was suffering from cholecystitis, other gastrointestinal symptoms had a low rate of incidence.History
The DASH-Sodium study was conducted following the end of the original DASH study to determine whether the DASH diet could produce even better results if it were low in salt. [1]. Primarily the researchers were interested in gaining more insight into the effect of sodium reduction when combined with the DASH diet. Design of the trials for the DASH-Sodium study were conducted and the trials took place from September 1997 through November 1999. Like the previous study, it was based on a large sample (412 participants) and was a multi-center, randomized, outpatient feeding study. [7]. The participants were adults with prehypertension or stage 1 hypertension (average systolic of 120 to 159 mm Hg & average diastolic of 80 to 95 mm Hg) and were randomly assigned to one of two diet groups. [6]. The two randomized diet groups were the DASH diet and a control diet that mirrored an “average American diet”, and which was somewhat low in key nutrients such as potassium, magnesium and calcium. After being assigned to one of these two diets, and within their assignment the participants ate foods differentiated by 3 distinct levels of sodium content, corresponding to 3,000 mg, 2,400 mg or 1,500 mg/day (hi, intermediate or low), in random order, for 30 consecutive days. [6]. During the two week run-in phase, all participants ate the high sodium control diet. The 30 day intervention phase followed, in which subjects ate their assigned diets at each of the aforementioned sodium levels (high, intermediate and low) in random order, in a crossover design. [7]. During the 30 day dietary intervention phase, each participant therefore consumed his or her assigned diet (either DASH or control) at all three sodium levels.Conclusions
The primary outcome of the DASH-Sodium study was systolic blood pressure at the end of the 30 day dietary intervention periods. The secondary outcome was diastolic blood pressure. The DASH-Sodium study confirmed that reductions in sodium intake correlated with significantly lower systolic and diastolic blood pressures in both control and DASH diets. Study results indicate that the quantity of dietary sodium in the control diet was twice as powerful in its effect on blood pressure as it was in the DASH diet. Importantly, the control diet sodium reductions from intermediate to low correlated with greater changes in systolic blood pressure than those same changes from high to intermediate (change equal to roughly 40 mmol per day, or 1 gram of sodium). As stated by Sacks, F. et al., reductions in sodium intake by this amount per day correlated with greater decreases in blood pressure when the starting sodium intake level was already at the U.S. recommended dietary allowanceDietary Reference Intake
The Dietary Reference Intake is a system of nutrition recommendations from the Institute of Medicine of the U.S. National Academy of Sciences. The DRI system is used by both the United States and Canada and is intended for the general public and health professionals...
, than when the starting level was higher (higher levels are the actual average in the U.S.). These results led researchers to postulate that the adoption of a national lower daily allowance for sodium than the currently held 2,400 mg could be based on the sound scientific results provided by this study. [7].
The DASH diet and the control diet at low salt levels were both successful in lowering blood pressure, but the largest reductions in blood pressure were obtained by eating a combination of these two (i.e., a low-salt version of the DASH diet). The effect of this combination at a sodium level of 1,500 mg/day was an average blood pressure reduction of 8.9/4.5 mm Hg (systolic/diastolic). The hypertensive subjects experienced an average reduction of 11.5/5.7 mm Hg. [6]. The DASH-sodium results indicate that low sodium levels correlated with the largest reductions in blood pressure for participants at both normative and hypertensive levels with the hypertensive participants showing the greatest reductions in blood pressure overall. Moreover, the African-American study participants showed particularly significant reductions in blood pressure.[1].
External links
- VIDEO - Which Diet Works: A Nutritional Review, Gail Underbakke, MS, RD, speaks at the University of Wisconsin School of Medicine and Public Health
- DASH A Diet for all diseases
- DASH for Women
- Your Guide to Lowering Blood Pressure, from NHLBI
- Your Guide to Lowering Your Blood Pressure with the DASH Eating Plan, from NHLBI
- The DASH diet for high blood pressure: From Clinical trial to dinner table, from Cleveland Clinic Journal of Medicine
- Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure JNC Express, from NHLBI
Related Books
- Delicious DASH Flavours: The proven, drug-free, doctor-recommended approach to reducing high blood pressure by Sandra Nowlan ISBN 978-0887807664
- The DASH Diet Action Plan: Based on the National Institutes of Health Research, Dietary Approaches to Stop Hypertension by Marla Heller, MS, RD ISBN 978-0976340812