Hypertension: 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.^8,9 The DASH study was predicated on the observation that vegetarian diets are associated with markedly reduced risk of hypertension.

Some investigators have carried these observations a step further. Vegetarian and vegan diets reduce blood pressure in both normotensive and hypertensive individuals, and have the potential to reduce or eliminate medication use in some patients.¹⁰ 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 production of nitric oxide, an important vasodilator.

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.^11-14 Saturated fat appears to influence blood viscosity.¹⁵ A higher proportional intake of fatty acids from polyunsaturated sources (linoleic acid and alpha-linolenic acids), compared with saturated fats, is associated with a lower risk for developing hypertension.¹⁶

Vegetables and fruits are rich in potassium, which influences blood pressure. Potassium, from either food or supplements, reduces blood pressure and stroke risk.¹⁷ Fruits and vegetables are rich potassium sources. Some evidence also suggests that fruits and vegetables may lower blood pressure by providing antioxidant flavonoids that up-regulate endothelial nitric oxide production,^18,19 and suppressing enzymes involved in the generation of superoxide radicals²⁰ that are known to reduce nitric oxide availability.

Sodium intake above physiologic need is related to the development of hypertension.²¹ Hypertension is rare in societies whose dietary sodium intake is very low.²² A study determined that 9% to 17% of the risk for hypertension in Western countries was attributable to dietary sodium alone.²³ 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

Additional considerations include:

• Limiting alcohol. In excess of moderate consumption (1-2 drinks/day), alcohol intake raises the risk for developing hypertension.²⁴ The relationship between moderate alcohol intake and hypertension is complicated, and studies have found a lower risk for hypertension-related mortality in moderate drinkers, even in those with hypertension, compared with persons who rarely or never drink alcohol.^25,26
• Folic acid. The Nurses' Health Study found that women consuming the highest amounts of folate from diet and supplements (> 1000 µg per day) had only one third the risk for developing hypertension than did women consuming less than 200 µg per day.²⁷ One possible explanation is that folate is an important cofactor for nitric oxide synthase and subsequent nitric oxide generation.
• Vitamin C. Dietary reference intakes (DRI) of vitamin C may not be adequate in persons at risk for hypertension. Studies show that blood pressure rises as vitamin C depletion occurs in humans,²⁸ and higher vitamin C intakes are associated with lower blood pressure.²⁹ However, there do not appear to be any additional blood pressure-lowering effects of vitamin C over an intake of 500 mg per day.³⁰
• Healthy body weight. The Nurses' Health Study and the Health Professionals Follow-Up Study found a dose-response relationship between weight and risk for hypertension, and this risk included persons in the upper range for "normal" body weight.³¹ 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 Chapter.
• Regular physical activity. Researchers have estimated that physical inactivity contributes 5% to13% of the risk for hypertension.²³ Energy expenditure in the form of vigorous activity,³² or even walking and leisure-time physical activity, lowers the risk for developing hypertension.³³

Orders

Vegetarian diet, low fat. Foods rich in vitamin C and potassium should be encouraged.

Sodium less than 2 g daily.

See Basic Diet Orders.

Smoking cessation and alcohol restriction, if applicable.

Individualized exercise prescription to increase physical activity, as appropriate. Consultation with physical therapist or exercise physiologist as needed.

What to Tell the Family

Hypertension usually has no symptoms, but can be deadly. It is important for the patient and the family to have their blood pressure checked regularly and to adhere to the prescribed treatment plan. A good-quality home blood pressure monitor makes tracking and treating hypertension much easier.

Hypertension is not treated with medication alone. Dietary and lifestyle changes can help reduce blood pressure and decrease, sometimes even eliminate, the need for medication. The family can support and enhance the patient's adherence to the recommended diet. Because overweight and hypertension sometimes run in families, it is important for the entire family to shift to healthier eating and exercise patterns. Smoking cessation and alcohol restriction should be encouraged.