August 10, 2007
A relatively simple and inexpensive measurement, blood pressure (BP) tells much about a person’s current health and risk for future problems. Sustained high BP, or hypertension, represents a risk for both cardiovascular disease and stroke, and frequently appears as a manifestation of other medical conditions. According to the American Heart Association, one in three U.S. adults has high BP, but 30% of them don’t know it.
Regulation of BP involves a complex interaction of multiple hormones and organ systems. While genetics play a major role in chronic high BP, research implicates weight, exercise and diet as key factors in the equation for keeping a lid on BP.
Decades ago, the medical community recognized salt and sodium restriction as the primary dietary intervention for hypertension. However, in recent years, rigorous studies on the effect of dietary patterns on BP highlight a number of food groups and other nutrients that play a role in BP control. U.S. Department of Health and Human Services and USDA’s Dietary Guidelines for Americans 2005 and the Seventh Report of the Joint National Committee on the Prevention, Detection, Evaluation and Treatment of High Blood Pressure, Bethesda, MD, cite the Dietary Approaches To Stop Hypertension, the DASH eating plan, as a preferred lifestyle modification, along with reduced sodium intake, maintenance of normal weight and regular physical activity for managing hypertension.
The DASH eating plan consists of a diet rich in fruits, vegetables and lowfat dairy products. Overall, the diet provides ample potassium, calcium and fiber—nutrients often lacking in the typical American diet—which appear to influence BP. One study in the May 2003 issue of Hypertension, Journal of the American Heart Association examined the data from the DASH-sodium Trial (and found that the DASH diet acted like a natural diuretic, making it valuable for individuals with high sodium sensitivity, a group that responds best to diuretic medications.
Research on another similar healthy eating pattern, the Mediterranean diet, demonstrates an inverse relationship with both systolic and diastolic BP in non-hypertensive individuals (American Journal of Clinical Nutrition, 2004; 80:1012-18). A statistical analysis on various dietary components associates vegetables, fruits and olive oil with lower BP, and cereals, meats and meat products, and ethanol with higher BP. The higher consumption of olive oil (with its monounsaturated fats) in the Mediterranean diet represents its major difference from the DASH diet and might offer an additional benefit in a healthy eating pattern for BP control.
Numerous studies document the relationship between sodium and BP, and subgroups in the general population with sodium sensitivity, generally blacks and those over 50. Health authorities worldwide recommend a dietary intake of no more than 2,300 to 2,400 mg of sodium per day for the general population, a significantly lower level than most people consume, naming processed foods as the main culprit for the excess dietary sodium. However, some question the cost-benefit ratio of limiting sodium for all when only the salt-sensitive individuals need to do so. Despite the controversy and the challenges of taste, safety and convenience in reduced-sodium foods, regulatory agencies and advocacy groups in most developed countries pressure the food industry to reduce salt and sodium-containing ingredients.
Other minerals play a role in managing BP. Potassium works with sodium to maintain water balance, regulate muscle contractions and other functions. Epidemiological studies indicate that a high potassium intake results in lower BP levels. Nutrition experts agree that fruits and vegetables can easily supply the necessary levels of potassium. In fact, several observational and DASH diet studies show high consumption of fruits and vegetables results in higher potassium intake and a hypotensive effect. However, economic and taste barriers make achieving the efficacious level of fruit and vegetable intake difficult for many. Potassium-fortified foods might offer a solution. A clinical trial using a slow-release potassium chloride supplement shows that a modest dose, equivalent to five servings of fruits and vegetables, reduces BP in healthy volunteers without side effects usually associated with higher therapeutic levels of potassium supplementation.
Adding value with dairy
Calcium also plays a role in lowering BP. Some epidemiological studies associate a high dietary calcium intake with lower BP and risk for stroke. Several studies illustrate a positive relationship between high milk and/or dairy intake and decreased risk for heart disease and stroke. In the DASH diet, the addition of low-fat dairy along with the high consumption of fruits and vegetables results in a greater reduction of BP, thereby making it a key element in this eating plan.
Dairy might offer more benefit beyond its important mineral content. Peter Huth, director of regulatory and research transfer, Dairy Management, Inc™, Rosemont, IL, says that research on hydrolyzed whey protein isolate (WPI) in animals and humans demonstrates a reduction in systolic and diastolic BP from peptides that inhibit angiotensin-converting enzyme (ACE), but without the side effects of a prescription drug. “While no long-term studies have been done on this natural component,” he says, “an unpublished clinical study conducted at the University of Minnesota on a hydrolyzed WPI from Davisco Foods (Eden Prairie, MN) showed that 20 grams is as effective as the DASH diet in lowering BP. This ingredient may be an effective adjunct to conventional dietary and medical interventions for high BP.” He also points out that, in Europe and Japan, patented versions of hydrolyzed fluid milk that exhibit ACE-inhibiting action have been available for years.
Several other dietary components and ingredients might also influence BP. A recent mega-analysis of 25 studies on dietary fiber found an increased intake by subjects with hypertension resulted in lower BP in 8 week or longer interventions. Research on garlic, omega-3 fatty acids, dark chocolate, oats and soy protein point to potential benefits, but still need further study.
Angela M. Miraglio, M.S., R.D., is a Fellow of the American Dietetic Association from Des Plaines, IL. Her firm, AMM Food & Nutrition Consulting, provides communications and technical support to the food and beverage industry. She can be reached at [email protected].
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