What is high blood pressure?
Blood pressure is the force of blood against artery walls. It is measured in millimeters of mercury (mm Hg) and recorded as two numbers-systolic pressure (as the heart beats) over diastolic pressure (as the heart relaxes between beats). Both numbers are important (see table on right)
Blood pressure rises and falls during the day. But when it stays elevated over time, then it's called high blood pressure. High blood pressure is dangerous because it makes the heart work too hard, and the force of its blood flow can harm arteries.
High blood pressure often has no warning signs or symptoms. Once it occurs, it usually lasts a lifetime. If uncontrolled, it can lead to heart and kidney disease and stroke.
High blood pressure affects about 50 million-or 1 in 4-adult Americans. High blood pressure is especially common among African Americans, who tend to develop it at an earlier age and more often than whites. It also is common among older Americans-about 60 percent of those age 60 and older have high blood pressure.
High blood pressure can be controlled if you take these steps:
- Maintain a healthy weight
- Be physically active
- Follow a healthy eating plan, which includes foods lower in salt and sodium
- If you drink alcoholic beverages, do so in moderation
- If you have high blood pressure and are prescribed medication, take it as directed
All steps but the last also help to prevent high blood pressure.
What is the DASH Diet?
Blood pressure can be unhealthy even if it stays only slightly above the optimal level of less than 120/80 mm Hg. The higher blood pressure rises above optimal, the greater the health risk. In the past, researchers tried to find clues about what in the diet affects blood pressure by testing various single nutrients, such as calcium and magnesium. These studies were done mostly with dietary supplements and their findings were not conclusive.
Then, scientists supported by the National Heart, Lung, and Blood Institute (NHLBI) conducted two key studies. The first was called "DASH," for Dietary Approaches to Stop Hypertension, and it tested nutrients as they occur together in food. Its findings showed that blood pressures were reduced with an eating plan that is low in saturated fat, cholesterol and total fat, and that emphasizes fruits, vegetables and lowfat dairy foods. This eating plan-known as the DASH diet-also includes whole grain products, fish, poultry and nuts. It is reduced in red meat, sweets and sugar-containing beverages. It is rich in magnesium, potassium and calcium, as well as protein and fiber.
The DASH study involved 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic pressures of 80-95 mm Hg. About 27 percent of the participants had hypertension. About 50 percent were women and 60 percent were African Americans.
DASH compared three eating plans: A plan similar in nutrients to what many Americans consume; a plan similar to what Americans consume but higher in fruits and vegetables; and the DASH diet. All three plans used about 3,000 milligrams of sodium daily. None of the plans were vegetarian or used specialty foods.
Results were dramatic: Both the fruits and vegetables plan and the DASH diet reduced blood pressure. But the DASH diet had the greatest effect, especially for those with high blood pressure. Further, the blood pressure reductions came fast-within 2 weeks of starting the plan.
The second study was called "DASH-Sodium," and it looked at the effect on blood pressure of a reduced dietary sodium intake as participants followed either the DASH diet or an eating plan typical of what many Americans consume. DASH-Sodium involved 412 participants. Their systolic blood pressures were 120-159 mm Hg and their diastolic blood pressures were 80-95 mm Hg. About 41 percent of them had high blood pressure. About 57 percent were women and about 57 percent were African Americans. Participants were randomly assigned to one of the two eating plans and then followed for a month at each of three sodium levels. The three sodium levels were: a higher intake of about 3,300 milligrams per day (the level consumed by many Americans); an intermediate intake of about 2,400 milligrams per day; and a lower intake of about 1,500 milligrams per day.
Results showed that reducing dietary sodium lowered blood pressure for both eating plans. At each sodium level, blood pressure was lower on the DASH diet than on the other eating plan. The biggest blood pressure reductions were for the DASH diet at the sodium intake of 1,500 milligrams per day. Those with hypertension saw the biggest reductions, but those without it also had large decreases.
Those on the 1,500-milligram sodium intake, as well as those on the DASH diet, had fewer headaches. Other than that and blood pressure levels, there were no significant effects caused by the two eating plans or different sodium levels.
DASH-Sodium shows the importance of lowering sodium intake -whatever your eating plan. But for a true winning combination, follow the DASH diet and lower your intake of salt.
How do I make the DASH?
The DASH diet used in the studies calls for a certain number of servings daily from various food groups. The number of servings you require may vary, depending on your caloric need. You should be aware that the DASH diet has more daily servings of fruits, vegetables, and whole grain foods than you may be used to eating. This makes it high in fiber, which can cause bloating and diarrhea in some persons. To avoid these problems, gradually increase your intake of fruit, vegetables, and whole grain foods.
Twenty-four hundred milligrams of sodium equals about 6 grams, or 1 teaspoon, of table salt (sodium chloride); 1,500 milligrams of sodium equals about 4 grams, or 2/3 teaspoon, of table salt. These amounts include all salt consumed-that in food products, used in cooking, and added at the table. Only small amounts of sodium occur naturally in food. Processed foods account for most of the salt and sodium Americans consume. So, be sure to read food labels to choose products lower in sodium.
You may be surprised at many of the foods that have sodium. They include soy sauce, seasoned salts, monosodium glutamate (MSG), baking soda, and some antacids-the range is wide.
Since it is rich in fruits and vegetables, which are naturally lower in sodium than many other foods, the DASH diet makes it easier to consume less salt and sodium. Still, you may want to begin by adopting the DASH diet at the level of 2,400 milligrams of sodium per day and then further lower your sodium intake to 1,500 milligrams per day.
How can you get started on the DASH diet?
It's easy. The DASH diet requires no special foods and has no hard-to-follow recipes.
Remember that some days the foods you eat may add up to more than the recommended servings from one food group and less from another. Similarly, you may have too much sodium on a particular day. But don't worry. Just be sure that the average of several days or a week comes close to what's recommended for the food groups and for your chosen daily sodium level.
One note: If you take medication to control high blood pressure, you should not stop using it. Follow the DASH diet and talk with your doctor about your drug treatment.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 6/6/2006
