Dietary Approaches to Reduce Blood Pressure

Elevated blood pressure remains an extraordinarily common and important risk factor for cardiovascular and renal diseases, including stroke, coronary heart disease, heart failure, and kidney failure. According to the most recent national survey (1999–2000), over 25% of adult Americans have hypertension (a systolic blood pressure ≥ 140 mmHg, a diastolic blood pressure ≥ 90 mmHg, or use of anti-hypertensive medication). Approximately 30% have pre-hypertension (a systolic blood pressure of 120–139 mmHg or diastolic blood pressure of 80–89 mmHg, not on medication). Pre-hypertensive individuals have a high probability of developing hypertension and carry an excess risk of cardiovascular disease compared to those with a normal blood pressure (systolic blood pressure < 120 mmHg and diastolic blood pressure < 90 mmHg). Recent data indicate that the prevalence of hypertension is increasing and that control rates among those with hypertension remain low. As individuals age, systolic blood pressure rises. Among adults over the age of 50, the lifetime risk of developing hypertension approaches 90%. Below the age of 50, hypertension is more common in men than women; the reverse is true above this age. On average, African-Americans tend to have higher blood pressure than non-African-Americans, as well as an increased risk of blood pressure-related complications, particularly strokeand kidney failure. Blood pressure is a strong, consistent, continuous, independent and aetiologically relevant risk factor for cardiovascular-renal disease. Importantly, there is no evidence of a blood pressure threshold, that is, the risk of cardiovascular and renal disease increases progressively throughout the range of blood pressure including the pre-hypertensive range. The greatest risk of blood pressure-related cardiovascular disease occurs in those with highest blood pressure. However, a relatively small fraction of the general population has such extreme levels of blood pressure. Because a much larger fraction of the population has lower levels of blood pressure, albeit still higher then normal, most blood pressure related cardiovascular events occur in those individuals with pre-hypertension or early Stage 1 hypertension. In fact, it has been estimated that almost a third of blood pressure-related deaths from coronary heart disease occur in individuals with blood pressure in the non-hypertensive range. Elevated blood pressure results from environmental factors, genetic factors, and interactions among these factors. Of the environmental factors that affect blood pressure (that is, diet, physical inactivity, toxins, and psychosocial factors), dietary factors have an especially prominent role in blood pressure homeostasis. A substantial body of evidence strongly supports the concept that multiple dietary factors affect blood pressure. Well-established dietary modifications that lower blood pressure are reduced sodium intake, weight loss, and moderation of alcohol consumption (among those who drink). Over the past decade, increased potassium intake and consumption of an overall healthy dietary pattern, termed the ‘DASH diet’, have emerged as effective strategies that also reduce blood pressure. The ‘DASH diet’ emphasizes fruits, vegetables, and low-fat dairy products and is reduced in saturated fat, total fat and cholesterol. A very high intake of omega-3 polyunsaturated fatty acids (fish oil) from pill supplements also lowers blood pressure but at very high doses that are commonly associated with side effects. In view of the continuing epidemic of blood pressure-related cardiovascular disease, efforts to reduce blood pressure in both non-hypertensive and hypertensive individuals are warranted. In non-hypertensive individuals including those with pre-hypertension, dietary changes that lower blood pressure have the potential to prevent hypertension and more broadly to reduce blood pressure and thereby lower the risk of blood pressure-related clinical complications. Indeed, even an apparently small reduction in blood pressure, if applied to a whole population, could have an enormous, beneficial impact. For instance, it has been estimated that a 3 mmHg reduction in systolic blood pressure could lead to an 8% reduction in stroke mortality and a 5% reduction in mortality from coronary heart disease. In uncomplicated stage I hypertension (systolic blood pressure 140–159 mmHg or diastolic blood pressure 90–99 mmHg), dietary changes can serve as initial treatment before the start of drug therapy. Among hypertensive individuals on drug therapy, dietary changes can further lower blood pressure and facilitate medication step down. Reference Appel, L. J., 2000 The role of diet in the prevention and treatment of hypertension. Current Atherosclerosis Reports 2, 521–528.