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DASH Diet: World Best and Healthiest Diet Plan 2014
The DASH Diet Eating Plan is rated by US News & World Reports as the Best
and Healthiest Diet Plan.
The DASH diet (Dietary Approaches to Stop Hypertension) is a dietary pattern
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) to prevent and control hypertension. The DASH diet 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 designed to be a well-balanced approach to eating for the
general public. It is now recommended by the United States 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. The diet reduced systolic blood pressure by 6 mm Hg and
diastolic blood pressure by 3 mm Hg in patients with high normal blood pressure,
now called "pre-hypertension." Those with hypertension dropped by 11 and 6,
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 1600 to 3100 dietary calories.
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 Institutes of Health] (NIH)
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 (RCT), 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 (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.
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.
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 (a �fruits and vegetables 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 (or
combination 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 anti-oxidant rich foods thought by some to retard or prevent chronic
health problems including cancer, heart disease and stroke.
 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. 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.
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. 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, subjects who were
compliant with the feeding program during the screening phase 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 were provided the diet to which they had been randomly assigned. 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. Each of the three diets contained the
same 3 grams (3,000 mg) of sodium, selected because that was the approximate
average intake in the nation at the time. 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.
The DASH trial showed that dietary patterns can and do affect blood pressure in
the high normal BP 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 with the control diet. The minority portion of the study
sample and the hypertensive portion 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. The fruits-and-vegetables diet was also
successful, although it produced more modest reductions compared with the
control diet (2.8 mm Hg systolic and 1.1 mm Hg diastolic). 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 and that the results were
generalizable to the target sample of the U.S. population.
Side effects were negligible, but the NEJM study reports that some subjects
reported constipation as a problem. 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, showing that the
fruits and vegetables and combination diets reduce constipation. Apart from only
one subject (on the control diet) who was suffering from cholecystitis, other
gastrointestinal symptoms had a low rate of incidence.
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 and also to examine the effects of different levels of sodium in
people eating the DASH diet. The researchers were interested in determining the
effects of sodium reduction when combined with the DASH diet as well as the
effects of the DASH diet when at three levels of sodium intake. The DASH-Sodium
trial was conducted 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 where the subjects were given all their
food.
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. The two randomized diet groups
were the DASH diet and a control diet that mirrored a �typical American diet�,
and which was somewhat low in key nutrients such as potassium, magnesium and
calcium. The DASH diet was the same as in the previous DASH study. After being
assigned to one of these two diets, the participants were given diets that
differed by 3 distinct levels of sodium content, corresponding to 3,000 mg,
2,400 mg or 1,500 mg/day (higher, intermediate or lower), in random order, for
30 consecutive days each.
 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. 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.
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 found that reductions in sodium
intake produced significantly lower systolic and diastolic blood pressures in
both the 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 allowance, 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. The U.S.
Dietary Guidelines for Americans recommend eating a diet of 2300 mg of sodium a
day or lower, with a recommendation of 1500 mg/day in adults who have elevated
blood pressure; the 1500 mg/day is the low sodium level tested in the
DASH-Sodium study.
The DASH diet and the control diet at the lower 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 lower-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. The
DASH-sodium results indicate that low sodium levels correlated with the largest
reductions in blood pressure for participants at both pre-hypertensive and
hypertensive levels, with the hypertensive participants showing the greatest
reductions in blood pressure overall.
Video
Dated 15 February 2014
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