Nearly half of all adults in the U.S. have high blood pressure. If not controlled, this generally symptomless “silent killer” can lead to se-rious consequences, including stroke, kidney disease, heart attack, and blindness. Fortunately, high blood pressure can be prevent-ed—and controlled—through healthy lifestyle choices. Engaging in regular physical activity, managing stress, limiting alcohol, quitting smoking, regularly taking blood pressure medications as prescribed, and achieving and maintaining a healthy weight are all important, and eating a healthy diet that’s low in salt and rich in vegetables and fruits is essential.
Extensive research has provided a pretty clear picture of how high blood pressure can be prevented and lowered through diet.
DASH: In 1997, a group of researchers
published the results of a clinical trial of the effects of dietary patterns on blood pressure. Called the DASH trial (Dietary Approaches to Stop Hypertension), this
11-week controlled feeding trial studied three diet patterns. One diet pattern in particular (now known as the DASH diet) substantially lowered blood pressure compare to the typical American diet. It also lowered total and LDL (bad) cholesterol levels without raising blood triglyceride levels (although it lowered HDL cholesterol levels as well). This heart-heathy diet was rich in fruits, vegetables, and low-fat dairy products, and reduced in total fat and saturated fat compared to a typical American diet. Since that time, many additional studies have confirmed the impact of a DASH-style diet on blood pressure and other markers of cardiovascular health.
Healthy fats and proteins: While the effectiveness of the DASH diet for lowering blood pressure has been convincingly prov-en, there is more that can be done within this overall pattern to boost heart health even more. To further refine the make-up of a heart-healthy dietary pattern, the Optimal Macronutrient Intake Trial to Prevent Heart Disease (OmniHeart) tested the effects of three variations of the DASH diet pattern:
- a low-fat, carbohydrate-rich diet similar to the DASH diet (where 58 percent of calories came from carbohydrate, 15 percent from protein, and 27 percent from fat);
- a pattern that replaced 10 percent of the carbohydrate with plant-based unsaturated fats (from olive oil, canola oil, and olive oil spread); and
- a pattern that replaced 10 percent of the carbohydrate with plant-based protein (mostly from sources like beans, legumes, nuts, and seeds).
In the latter two diets, the 10 percent reduction in carbohydrate was achieved by reducing grains and replacing some fruits with beans, legumes, nuts, or seeds to increase plant protein or unsaturated fats. Saturated fat was low (six percent of calories) in all diets. All three diets dramatically reduced blood pressure, total and LDL cholesterol levels, and estimated coronary heart disease risk (by 16 to 21 percent). But the best effects were seen when some carbohydrate was replaced with either protein or unsaturated fat. “This landmark trial showed that people shouldn’t fear healthy fats or protein,” said Dariush Mozaffarian, MD, DrPH, dean of the Friedman School and editor-in-chief of Tufts Health & Nutrition Letter. “But, regardless of carbohydrate, fat, or protein content, any of these diets were far better than a typical American diet for improving blood pressure and other cardiovascular risk factors. Choosing healthy foods matters.”
Salt and Other Minerals: A separate study published in 2001, the DASH-Sodium trial, found that eating healthier foods (like fruits, vegetables, and low- or nonfat dairy products) and lowering salt had separate, synergistic effects on blood pressure. High in-takes of sodium cause water retention—which means more blood volume, and therefore more pressure on the blood vessels (higher blood pressure).
Foods in the DASH diet are rich in micronutrients that lower blood pressure—like potassium and magnesium. Potassium (found in plant foods like sweet potatoes, bananas, oranges, leafy greens, and broccoli) counters the blood-pressure raising effect of sodium 
by helping the kidneys remove water from the body as urine. Magnesium (found in dark, leafy greens, whole grains, and legumes) helps the blood vessels relax, allowing them to stretch, which reduces blood pressure. Calcium (found naturally in many foods including dairy products, almonds, and dark, leafy greens) is also involved in the health of blood vessel walls. To help keep your blood pressure in a healthy range, focus on eating plenty of vegetables, fruits, nuts, legumes, and whole grains; healthy plant oils like olive, canola, and soybean oils; and dairy products and fish. “Limit intake of added sodium and sugar, red and processed meats, and refined carbo-hydrate,” says Alice H. Lichtenstein, DSc, director of the Cardiovascular Nutrition Laboratory at the Human Nutrition Research Center on Aging and executive editor of Tufts Health & Nutrition Letter. While potassium and magnesium supplements have been shown to modestly lower blood pressure, too much can be dangerous. “The best approach is to stick to healthy food choices,” says Lichtenstein.
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