Hypertension and Diet - Hypertension & Nutrition

Hypertension and Diet
TUFTS

High blood pressure or hypertension is a common medical problem and is a powerful and independent risk factor for cardiovascular disease (CVD). It is estimated that approximately 50 million US adults, roughly 25% of the population, have hypertension. Hypertension is defined as a blood pressure of >140 mm Hg (systolic) or >90 mm Hg (diastolic) or currently taking antihypertensive medications[1], [2]. The prevalence of hypertension increases with age, so that by age 60, 50% of people will have hypertension. Borderline blood pressure (120-139 mm Hg systolic or 80-89 mm Hg diastolic) also confers excess CVD risk.

Current national recommendations for the prevention and treatment of hypertension focus on non-pharmacological therapies, defined as lifestyle modifications [3], [4]. These include weight loss, reduced sodium intake, increased physical activity, limited alcohol consumption and adherence to the Dietary Approaches to Stop Hypertension (DASH) diet [5]. The DASH diet emphasizes consumption of fruits, vegetables, and low fat dairy products, including whole grains, poultry, fish, and nuts, with reduced fats, red meat, sweets, and sugar-containing beverages. As a result the DASH diet is reduced in total fat, saturated fat and cholesterol, is moderate in sodium (<3g/day) and has increased levels of potassium, calcium, magnesium and fiber [6].

The first study testing the DASH diet included 459 adults with slightly elevated blood pressure (<160 systolic and 80-95 diastolic) who were not on medication and were fed the typical American diet for three weeks before being randomly assigned to a diet rich in fruits and vegetables or one which also included low-fat dairy products and reduced saturated fat and cholesterol (DASH diet) [5], [6]. Sodium intake and body weight were kept constant. Persons with hypertension on the DASH diet (N=133) showed reduced systolic (-11.4 mm Hg and diastolic (-5.5 mm Hg) blood pressure compared to the control diet (p<0.001).

A follow-up study showed that in free living persons (not in a restricted study environment), the DASH diet was successful in reducing hypertension, from a 38% prevalence at baseline to 12% in the DASH diet group (p<0.001) compared to the group that was only given "advice" (one 30-minute session with an interventionist and printed material) [7]. The DASH intervention group had 18 sessions, individual or group, over a 6-month period to help effect the desired lifestyle changes.

In a subsequent study to determine the mechanism by which the DASH diet impacts blood pressure, data strongly suggested that the diet had a natriuretic action using an analysis of the pressure-natriuresis curve [8]. The mediations used to treat hypertension (b-blockers, calcium antagonist, and diuretics) have been shown to affect the pressure-natriuresis curve also.

The DASH diet has no negative side effects and is considered useful for CVD and diabetes. It is easy to teach patients but a number of sessions with the nutritionist/dietitian is recommended in order to help the patient to make the necessary changes as suggested by the study cited above [7]. The main messages of increased fruit and vegetable intake (5-6 cups/day), use of low fat dairy products and reduced intake of red meats and sweets are contained in the booklet Facts About the DASH Eating Plan produced by the National Heart, Lung and Blood Institute, which also includes seven days of menus and other tips.

While useful in the prevention and treatment of hypertension, all adults are thought to benefit from the DASH diet. It is also a useful approach to weight loss with its emphasis on low calorie fruits, vegetables and legumes, which are high in fiber and help to control hunger. In persons newly diagnosed with hypertension, it was shown to replace the need for the first line of medications. Long term studies have not been carried out to determine if this diet will prevent the development of hypertension over a long time period as hypertension is reported to increase with age.

Resources and Links: Hypertension as a Condition
Understanding High Blood Pressure
National Heart, Lung, and Blood Institute

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Acknowledgements and disclaimer | Date last modified: Friday, October 31, 2008