 |
|
|
Background
Current national guidelines aimed
at preventing and treating hypertension recommend controlling body
weight, reducing salt and alcohol consumption, and possibly increasing
dietary potassium. A vegetarian diet is also associated with lower
blood pressure (BP), although studies have not revealed what component(s)
of such a diet might be responsible.
The DASH study was designed to test the effects
of dietary patterns on blood pressure. Rather than using supplements
to study single nutrients, the study used whole foods. The diet
retained the BP benefits of a vegetarian diet but included enough
meat and dairy products to make it acceptable to the general population.
|
|
|
|
|
Subject characteristics
- 459 subjects
- aged 22 or older; average age 45
- 59% were African-American
- 51% were men, 49% were women
- initial BP: less than 160/95 mmHg
- average baseline BP: 132/85 mmHg
- 29% had Stage I hypertension (140-159/90-99 mmHg)
|
|
Study Design
After a 3 week control diet patterned
after the typical American diet, subjects were randomly assigned to one
of three diets which they followed for 8 weeks:
- Control diet (low in fruits, vegetables
and dairy foods, 37% of calories from fat)
- Fruit/vegetable diet (8-10 servings fruits
and vegetables, with fewer snacks and sweets than the control diet)
- Combination diet (8-10 servings fruits and
vegetables, 2-3 servings lowfat dairy products, 27% of calories from
fat)
All three diets were similar in salt, sodium and
alcohol content. Calorie intake was also controlled so that subjects maintained
their usual body weight. No specialty foods with fat substitutes were
used.
|
|
Key Results
- Fruit/Vegetable Diet reduced systolic BP by 2.8
mmHg and diastolic BP by 1.1 mmHg.
- Combination Diet reduced systolic BP by 5.5 mm
Hg and diastolic BP by 3.0 mmHg.
- Reductions in BP were greatest in hypertensive
subjects.
- Reductions occurred within two weeks of starting
diets and were maintained throughout the study.
- Reductions occurred regardless of ethnic group
or gender.
|
|
Conclusions
- A diet rich in fruits, vegetables and lowfat
dairy foods, with reduced saturated and total fat can substantially
lower blood pressure. This offers an efficacious nutritional approach
and possible alternative to medication in the treatment of mild hypertension,
and may prevent or delay medication of borderline hypertensives.
- Researchers estimate that if all Americans followed
the DASH diet and experienced similar results, coronary heart disease
and stroke would be reduced by 15% and 27% respectively, nationwide.
That translates into 225,000 fewer heart attacks and 100,000 fewer strokes
every year.
|
|
DASH - Sodium Trial
| As with any clinical trial, duplication of
results lends credibility. The National Heart, Lung and Blood Institute
(NHLBI) supported a second DASH study, results of which were presented
in May 2000 at the American Society of Hypertension annual meeting.
This study looked at the relationship between BP on the DASH diet
and various sodium intakes. |
|
|
Subject Characteristics
- 412 subjects
- aged 22 or older
- 57% were African-American
- 43% were men, 57% women
- initial BP: less than 160/95 mmHg
- 41% had Stage I hypertensionDiet)
|
|
Study Design
Subjects were randomly
assigned to either the Control or DASH diet (for descriptions see above).
Each of these diets was followed at three sodium levels:
- Higher - 3300 mg/day
(typical of the average American diet)
- Intermediate -
2400 mg/day
- Lower - 1500 mg/day
(considered a therapeutic level)
Key Results
- Reducing dietary
sodium lowered BP in both control and DASH diet participants.
- Biggest reduction
in BP was on DASH diet at lowest sodium intake (systolic BP decreased
by an average of 8.0 mmHg, diastolic BP by an average of 4.5 mmHg).
- Reductions in
BP were greatest in hypertensive subjects.
- Those on lower
sodium diet and on DASH diet had fewer headaches.
Conclusions
- Those with hypertension
should follow the DASH diet at a reduced sodium intake to help lower
their blood pressure
- African Americans
in particular can benefit from adopting an eating plan similar to that
of a lower sodium DASH diet.
- By reducing dietary
sodium, all Americans, and particularly those at risk for hypertension,
can decrease their chance of developing high blood pressure. Patients
aiming for a level as low as 1500 mg/day should consult a registered
dietitian for dietary advice.
|
|
Reference: A Clinical
Trial of the Effects of Dietary Patterns on Blood Pressure. New England
Jounal of Medicine 1997; 336:1117-24. |
|
 |