According to the American Heart Association (AHA), nearly half of Americans have high blood pressure. Many of them are not aware that they have high blood pressure because they have no symptoms. The Centers for Disease Control and Prevention estimate that 32% of American adults have high blood pressure. Another third have elevated blood pressure that is not quite in the hypertension range. High blood pressure was a contributing factor in more than 410,000 deaths in 2014. In the United States, hypertension rates are highest in the Southeast.
Blood pressure is measured as it pushes against the inside of artery walls. The low blood pressure point, when the heart is at rest (between beats, when the heart is refilling with blood), is called diastolic pressure; the high blood pressure point, when the heart beats (contracts), is called systolic pressure. The number for the systolic pressure is larger than the number for the diastolic pressure. Blood pressure is measured in millimeters of mercury (mmHg). The systolic reading is read and recorded first, and the diastolic pressure is read next. For example, if a person's high, or systolic, pressure is 118 and his or her low, or diastolic, pressure is 70, the blood pressure would be announced and recorded as 118/70 mm Hg, or 118 over 70. This falls into the normal range, according to the AHA. The AHA's recommended blood pressure levels are less than 120 mm Hg for systolic pressure and less than 80 mm Hg for diastolic pressure.
Blood pressure is considered elevated if the systolic pressure is 120–129 mm Hg with a diastolic pressure less than 80. Stage 1 hypertension is defined as having a systolic pressure of 130–139 mm Hg or a diastolic pressure of 80–89 mm Hg. Stage 2 is defined as having a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher. If the systolic pressure rises above 180 mm Hg or the diastolic pressure goes above 120, the person is considered to be in hypertensive crisis, and emergency care is needed. High blood pressure can have serious health consequences and is a major risk factor for stroke and heart attack.
There is not a known primary cause of hypertension, and in many cases the underlying cause cannot be determined. This is referred to as essential hypertension. If a specific cause has been found—usually kidney disease—the condition is referred to as secondary hypertension.
Several factors may be involved in the development of hypertension, including:
The AHA notes that high blood pressure is linked with metabolic syndrome, or insulin resistance syndrome. Metabolic syndrome is diagnosed when a patient has any three of these risk factors:
Symptoms are normally not present when blood pressure is high. Because of this, hypertension is often called the “silent killer.” When symptoms do occur, they usually include:
Hypertension is usually diagnosed by taking a person's blood pressure with a blood pressure cuff, known as a sphygmomanometer. Machines are also available that take it automatically, including home units. A regular annual physical examination is a good way to track blood pressure levels and overall health. The exam generally include taking the patient's pulse rate, respiratory rate, body temperature, and weight. During the exam, the medical professional inquires about past medical history, family medical conditions, medicine use, and other information helpful in diagnosing hypertension, including smoking habit, alcohol consumption, lifestyle, exercise, drug use, and food consumption. Other checks performed during the exam include feeling for pulses on the extremities, such as ankles; touching the abdomen, especially the aorta; and examining the eyes.
A hallmark of diets typically recommended to control high blood pressure is to eat foods rich in potassium and avoid foods high in sodium. Although some research in the 2010s suggested that sodium did not in fact raise blood pressure, the general consensus, which is reflected in dietary guidelines around the world, is that sodium restriction can help to reduce blood pressure, particularly in people who are more sensitive to its blood-pressure-raising effects. The AHA concluded that the DASH diet is effective. Diets like the DASH diet encourage eating more servings of fresh fruits and vegetables, which are naturally low in sodium. They also encourage keeping a check on total calories, fat, and refined carbohydrates. These diet strategies encourage a healthy weight and help balance levels of sodium and other dietary minerals.
Though a low-fat diet is recommended as part of a healthy lifestyle, there is no direct link between fat, particularly saturated fat, and development of hypertension. Omega-3 fatty acids may offer slight protective benefits; studies have shown minor reductions in blood pressure levels in people taking higher doses (more than 3 grams) of omega-3 fatty acids. Other studies have found conflicting results, so further research is needed. Vitamins B6, C, D, and E may all also play roles in the prevention and treatment of hypertension, but studies are ongoing and patients should consult their physicians before taking any vitamins or other dietary supplements.
Patients with stage 1 hypertension may be advised to take antihypertensive medication. Numerous drugs are available, and the choice of medication depends on the stage of hypertension, side effects, other medical conditions the patient may have, and other medicines the patient is taking. If treatment with a single medication fails to lower blood pressure to the desired level, a different drug may be tried or added to the first. Patients with more severe hypertension may initially be given a combination of drugs. Patients should never stop taking any medication without checking with their physician.
Potassium does the opposite of sodium and helps to lower blood pressure. Potassium is best obtained from foods rather than supplements, although supplements have been shown to be helpful. Foods rich in potassium include apricots, avocados, bananas, melons, kiwis, lima beans, oranges, prunes, dates, spinach, tomatoes, squash, potatoes, and whole grains. Fresh fruits and vegetables are low in sodium and rich in potassium and fiber as well as other vitamins and minerals.
Plant proteins also may help lower blood pressure. Examples of plant proteins include soy, beans, peas, lentils, and nuts. Fresh produce is recommended rather than canned because manufacturers may add sodium to help preserve canned products; the same is true for fish and poultry.
Research in the 2010s pointed to a link between insulin resistance and hypertension. Insulin resistance tends to increase as the population becomes more overweight by eating a modern Western diet high in refined carbohydrates, and people with high insulin levels tend to have multiple symptoms of metabolic syndrome. This has led some experts to posit a link between high sugar consumption and hypertension. Eating sugar and carbohydrates raises insulin, and raised insulin levels appear to lead to the accumulation of salt and fluid in the body, which leads to high blood pressure. Low-carbohydrate diets have been shown to decrease insulin levels and also lower blood pressure.
In the 1990s, scientists from the National Heart, Lung, and Blood Institute (NHLBI) conducted key studies to look at the effects of diet on blood pressure. These trials, called DASH (Dietary Approaches to Stop Hypertension), showed that an eating plan low in saturated fat, cholesterol, and total fat and high in fruits, vegetables, whole grains, lean meats/fish/poultry, and low-fat dairy foods helped to lower blood pressure. DASH trials also followed the effects of a reduced-sodium diet on blood pressure. As a result, a comprehensive eating plan (the DASH diet) was developed with specific suggestions for each food group. As of 2018, the AHA still recommended the DASH diet and had published research indicating that this diet could dramatically lower blood pressure in hypertensive patients.
Vegetarian diets also may help keep blood pressure low, as may eating more fiber and monounsaturated fats. The OmniHeart diet is similar to DASH but emphasizes a particular food group, such as protein. Other lifestyle changes, such as quitting cigarette smoking and increasing physical activity, are also recommended.
It is important to involve a physician or registered dietitian in diet planning. Credible organizations, such as the American Heart Association, the Academy of Nutrition and Dietetics, or the National Heart, Lung, and Blood Institute, may also offer information on antihypertensive diets. People with high blood pressure should not rely on fad diets for quick weight loss or blood pressure fixes.
Though hypertension can be managed, it cannot be cured, and people with hypertension must work to control their blood pressure levels and keep them within normal ranges. The preferred way to do so is with careful monitoring of blood pressure and a combination of lifestyle and diet changes, as well as possible use of medications.
Though excessive salt intake may be a trigger for high blood pressure, not everyone is sensitive to salt. Some people have high blood pressure for other reasons, such as heredity. Nevertheless, about one-half of people with high blood pressure are thought to be “salt sensitive,” with high sodium intake resulting in raised blood pressure levels. Being overweight or obese are other factors affecting blood pressure, so developing dietary and lifestyle habits aimed at maintaining or losing weight are encouraged. Closely following a diet, such as DASH or one prescribed by a physician, to keep weight in the normal range helps control blood pressure. Many patients have successfully lowered their blood pressure by reducing the carbohydrate content of their diets.
See also Alcohol consumption ; Coronary heart disease ; DASH diet ; Diuretics and diets ; Low-fat diet ; Obesity ; Sodium ; Stroke .
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Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, firstname.lastname@example.org, http://www.eatright.org .
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Teresa G. Odle
Revised by Amy Hackney Blackwell, PhD