Dietary Tack Can Help Dash Hypertension

If you have high blood pressure--and you’re tired of hearing messages about what you shouldn’t eat (such as salt)--you’ll like the DASH diet.

The Dietary Approaches to Stop Hypertension diet emphasizes a variety of healthful foods--grains and grain products, fruits, vegetables and low-fat dairy foods. In a recent study involving more than 450 men and women (some with hypertension and some with normal blood pressure), the diet was found to significantly reduce blood pressure, even when participants didn’t decrease salt intake.

In the study, researchers compared the diet with two other eating plans--the “typical” American diet and the typical American diet with added fruits and vegetables. All three diets contained about the same amount of sodium and a similar number of calories. Within two weeks, the average systolic blood pressure dropped among participants who followed the diet enriched with fruits and vegetables. But it fell even further in those who followed the DASH diet.

Researchers are still not sure why the DASH diet works, but blood pressure experts suspect it’s related to the high levels of certain minerals, such as potassium, magnesium and calcium, in the grains, fruits and vegetables, and dairy products. The diet contains up to two times as much of these nutrients as are typically consumed by the average American. (For example, a person eating 2,000 calories per day on the DASH diet consumes about 4,700 milligrams of potassium per day; at that caloric level, the typical American diet contains only about 2,600 milligrams.) The diet is also rich in vitamin C, a nutrient that has been shown to help lower blood pressure in numerous studies.

This is not to suggest that the DASH diet should be used as an alternative to cutting back on salt. Ideally, it should be used in addition to it.

Researchers proved the value of this combination approach with a second study that is often referred to as DASH-Sodium. For three months, study participants ate either a typical American diet or the DASH eating plan. Each month, the amount of sodium in both diets was changed, and blood pressures were measured. The results: The lower the sodium (salt) intake--on either diet--the lower the average blood pressure. But the greatest lowering of pressure was seen when the DASH diet was combined with strict sodium restriction. In men and women with hypertension, this combination produced an average drop in systolic blood pressure (the top number) of almost 12 points.

The benefits of the DASH diet aren’t limited to people with high blood pressure. It also lowers blood pressure in those with supposedly “normal” levels and could help prevent hypertension from developing. Given the fact that Americans age 55 and over have a 90% likelihood of developing hypertension during their lifetime, more people should consider starting the DASH diet before they develop high blood pressure.

In fact, the benefits of the diet don’t even appear to be limited to its effect on blood pressure. In addition to lowering blood pressure, the diet can also help reduce blood cholesterol levels (which is not surprising, considering that the diet is low in fat--particularly saturated fat--and cholesterol, and rich in fiber). Compared with people eating a typical American diet, those on the DASH diet have lower total and LDL (or “bad”) cholesterol levels. In one study, total cholesterol levels were reduced by about 7% and LDL cholesterol levels by about 9%. And although HDL (or “good”) cholesterol levels also dropped, the overall effect on blood lipids was thought to be beneficial.

Men and women following the DASH diet also had lower levels of homocysteine in their blood, which may reduce their risk of cardiovascular disease. (High levels of this amino acid have been linked to an increased risk of heart attack and stroke.) The lower levels of homocysteine are probably related to the fact that the DASH diet is rich in folic acid, which--along with some other B vitamins--can have this effect.

Unfortunately, as with any diet, the DASH diet is difficult for many people. Even when it is strictly adhered to, its effect--though helpful--is frequently not enough. That’s why other methods of controlling blood pressure, such as weight loss and exercise, should be used in conjunction with the diet, and why many people (particularly those with moderate or severe hypertension) still require medications.

For more information about the DASH diet (as well as sample daily menus and simple recipes), contact the National Heart, Lung, and Blood Institute at (301) 592-8573 or visit its Web site at www.nhlbi.nih.gov.

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Snapshot of a Daily Diet That Aims to Reduce Elevated Blood Pressure

Recommended intake of the various food groups is based on a 2,000-calorie daily diet; the number of servings will change depending on the number of calories eaten.

Grains and grain products: 7-8 servings a day (1 serving is, for example, 1 slice of bread or 1/2 cup cooked rice or pasta)

Vegetables: 4-5 servings a day (1 serving is, for example, 1/2 cup cooked vegetables or 6 ounces of vegetable juice)

Fruits: 4-5 servings a day (1 serving is, for example, 1 medium fruit or 6 ounces of fruit juice)

Low-fat dairy foods: 2-3 servings a day (1 serving is, for example, 8 ounces of milk, 1 cup of yogurt or 1 1/2 ounces of cheese)

Meats, poultry and fish: No more than 2 servings a day (1 serving is, for example, 3 ounces of cooked meat, poultry or fish)

Nuts, seeds and dry beans: 4-5 servings a week (1 serving is, for example, 1 1/2 ounces of nuts, 1 1/2 ounces of seeds or 1/2 cup cooked beans)

Fats and oils: 2-3 servings a day (1 serving is, for example, 1 teaspoon of oil)

Sweets: 5 servings a week (1 serving is, for example, 1 tablespoon of jelly or jam or 1 tablespoon of sugar)

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Dr. Jonathan Fielding is the director of public health and the health officer for the Los Angeles County Department of Health Services. Dr. Valerie Ulene is a board-certified specialist in preventive medicine practicing in Los Angeles. Their column appears the second and fourth Mondays of the month. Send questions by e-mail to ourhealth@dhs.co.la.ca.us. They cannot respond to every query.