High Blood Pressure: Nutritional Considerations
Nutritional factors play a large role not only in reducing the risk that hypertension will occur, but also in managing the condition after it has been diagnosed. The Dietary Approaches to Stop Hypertension (DASH) study showed that diets rich in fruits and vegetables and reduced in saturated fat can lower both the risk for high blood pressure and assist with blood pressure control in hypertensive persons. The DASH study was based on the observation that vegetarian diets are associated with significantly reduced risk of hypertension.
Some investigators have carried these observations a step further. Vegetarian and vegan diets reduce blood pressure in both normal and hypertensive individuals and have the potential to reduce or eliminate medication use in some patients. The benefits of a vegetarian diet are probably the combined result of several factors, in addition to lower body weight in vegetarians. These include lower saturated fat and cholesterol intakes; greater amounts of potassium, folate, vitamin C, and flavonoids; and, possibly, a greater presence of L-arginine, an amino acid involved in blood vessel functioning.
Possible mechanisms underlying these results may include a combination of the following:
- Reducing or eliminating meat may influence blood viscosity. Numerous studies have linked beef, veal, lamb, poultry, and animal fat to high blood pressure. Saturated fat appears to increase the viscosity (or thickness) of the blood. A higher proportional intake of fatty acids from polyunsaturated sources, compared with saturated fats, is associated with a lower risk for developing hypertension.
- Vegetables and fruits are rich in potassium, which influences blood pressure. Potassium, from either food or supplements, reduces blood pressure and stroke risk. Fruits and vegetables are rich potassium sources. Some evidence also suggests that fruits and vegetables may lower blood pressure by providing antioxidants.
- Sodium intake above the normal daily need is related to the development of hypertension. Hypertension is rare in societies whose dietary sodium intake is very low. A study determined that 9 to 17 percent of the risk for hypertension in Western countries was attributable to dietary sodium alone. The principal sources of sodium are canned foods, snack foods, discretionary use of salt in food preparation or consumption, and dairy products. In their natural state, vegetables, fruits, grains, and legumes are very low in sodium.
- Limiting alcohol: Excessive alcohol consumption (more than one to two drinks per day) raises the risk for developing hypertension. The relationship between moderate alcohol intake and hypertension is complicated, and studies have found a lower risk for hypertension-related death in moderate drinkers, even in those with hypertension, compared with persons who rarely or never drink alcohol.
- Folic acid: The Nurses' Health Study found that women consuming the highest amounts of folate from diet and supplements (less than or equal to 1,000 µg per day) had only one-third the risk for developing hypertension than did women consuming less than 200 µg per day.
- Vitamin C: Dietary reference intakes of vitamin C may not be adequate in persons at risk for hypertension. Studies show that blood pressure rises as vitamin C deficiency occurs in humans, and higher vitamin C intakes are associated with lower blood pressure. However, there do not appear to be any additional blood pressure-lowering effects of vitamin C over an intake of 500 milligrams per day.
- A healthy body weight: The Nurses' Health Study and the Health Professionals Follow-Up Study found that the higher a person's weight above normal, the higher the risk for hypertension. The same diet changes used for blood pressure regulation diets rich in vegetables and fruits and low in meat, particularly vegetarian diets, also help reduce body weight. See Obesity.
- Regular physical activity: Researchers have estimated that physical inactivity contributes 5 to 13 percent of the risk for hypertension. Energy expenditure in the form of vigorous activity, or even walking and leisure-time physical activity, lowers the risk for developing hypertension.