The DASH diet originated out of
clinical studies by the National Institute
of Health. These studies were designed
to test which diets are best suited to
reducing hypertension. The National
Institute of Health examined three
different diets in the clinical studies and
then examined their results.
The tests took place at five different
medical centers including John Hopkins
University in Baltimore, Maryland;
Kaiser Permanente Center for Health
and Research in Portland, Oregon; Duke
University Medical Center in Durham,
North Carolina; Brigham and Women’s
Hospital in Boston, Massachusetts; and
Pennington Biomedical Research Center
in Baton Rouge, Louisiana.
In the studies, two experimental diets
were used and compared against a third
control diet. The control diet was low in
key nutrients, such as calcium,
potassium, fiber, and magnesium, with
high levels of fat, which was similar to
the “typical American diet.” The first
experimental diet was similar to the
control diet, but it included a larger
portion of fruits and vegetables and
fewer snacks and sweets. The second
experimental diet was the DASH diet,
which is high in fruits and vegetables,
high in fiber, low in fat, and has higher
protein than the control diet.
Nearly 10,000 people were screened
for the clinical study, with only 459
people being chosen. These 459 people
were close to the demographic target
population, who were men and women
averaging an age of 46 with an average
blood pressure of 160/80. This would
be considered high blood pressure.
African-Americans and other ethnic
groups made up 67% of the clinical trial
group. Due to the fact that minority
populations are more likely to suffer
from high blood pressure, this was a
representative sample. Women made up
49% of the study group.
Study participants ate one of the
three randomly assigned diets for eight
weeks. Each diet contained about 3400
mg of sodium. Alcohol was limited to
two beverages per day and caffeine was
limited to three beverages per day.
Study Results
The study showed that the DASH
diet lowered blood pressure an average
of 5.5 mm Hg for systolic blood
pressure and 3.0 mm Hg for diastolic
blood pressure compared with the
control group. The minority and
hypertensive study subjects had the
greatest reduction in blood pressure. The
diet that was similar to the control diet
but included more fruits and vegetables
was also successful in dropping blood
pressure, but to a more moderate degree.
For all test subjects, even those who
were not hypertensive, the DASH diet
dropped blood pressure within two
weeks of starting the diet.
Side effects of the study were a
reduction in constipation for the DASH
diet group and for the fruits and
vegetables group, showing that fruits and
vegetables reduce constipation.
Continued Study
An additional study was conducted
at the end of the original DASH study to
determine if lowering sodium in
conjunction with the DASH diet would
produce even better results. It was based
on a large sample of participants
numbering 412 people, in a multi-center,
randomized clinical study.
The participants were adults with
prehypertension or were hypertensive.
They were randomly assigned to two
different diet groups. One group was the
DASH diet group and the control group
was given an “average American diet.”
The participants were further broken
down into three subgroups with three
different levels of sodium being 3000
mg, 2400 mg, or 1500 mg. The
participants ate these diets for a total of
30 days.
Results
Both the DASH diet and control diet
at lower sodium levels reduced blood
pressure. The greatest reduction in blood
pressure was from the 1500 mg per day
DASH diet. There was an average of
8.9/4.5 mm Hg blood pressure reading
in this study group. Hypertensive
participants experienced an even greater
reduction in blood pressure averaging
11.5/5.7 mm Hg.
Conclusion
Lowering sodium to 1500 mg per
day will decrease blood pressure
somewhat, but implementing the DASH
diet at 1500 mg per day will create
incredible results. There is sound
scientific evidence to support the
effectiveness of the DASH diet to
reverse hypertension.
