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The Ups and Downs of Hypertension

What's the most important number to know? Not your net worth, your age, or even the PIN number for your ATM card. It's your blood pressure. You should know this number and what it means. Nearly one-third of people with high blood pressure don't know they have it.

Why is blood pressure important? Because high blood pressure, also called hypertension, affects millions of people in the U.S. and Canada. It is the major treatable risk factor for heart disease and stroke. Yet only half of those with hypertension are being treated for it, and only half of those being treated have the disorder under control. In the past 20 years, deaths from coronary artery disease in the U.S. have fallen by 53%, and from stroke by nearly 60%—in large part because of better detection of and treatments for hypertension and heart disease. But recently the rate of improvement has slowed. Compared with 1991, a smaller percentage of people are aware of the dangers of hypertension and are taking steps to prevent and control it. Here is what everybody should know about hypertension, including the latest findings and recommendations from the Sixth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure.

Note: Medications for hypertension are beyond the scope of this article and—if you need them—should be discussed with your doctor.

How blood pressure turns into hypertension

Blood pressure is created by the pumping of your heart—a variable force that moves blood through the circulatory system. When your heart contracts, blood flows into the arteries, and at the end of the contraction the pressure exerted on the walls of the vessels is at its highest. Then as the heart relaxes, blood flows from the veins into the heart, and the pressure falls to its lowest level. Thus blood pressure is expressed as two numbers: systolic (high point, during a contraction) and diastolic (low point, between heart beats). A complex bodily system regulates blood pressure, which fluctuates normally according to your activity level and many other factors. The main regulators of blood pressure are small blood vessels called arterioles, which widen and constrict, causing pressure to fall and rise.

But when the regulatory system goes awry—for instance, if the arterioles stay constricted—blood pressure stays chronically high. In most cases the cause of this condition is unknown—this is called "essential" hypertension. Untreated hypertension can damage the arteries, resulting in damage to the brain, heart, and kidneys. The major risk factors are advancing age, a high sodium and/or alcohol intake, being overweight, being sedentary, and a family history of hypertension. For reasons that remain unclear, the incidence is also higher among black people, poor people, and those with lower educational levels. But anybody in any walk of life can develop hypertension.

Everybody, at any age, should have a blood pressure check every two years. If you have elevated pressure, a family history of heart disease, or other risk factors, you may need more frequent monitoring.

How can I prevent hypertension? Besides taking drugs, if that becomes necessary, how can I control it if I have it?

It's not certain that you can prevent it, but it's reasonable to think that the same practices that help control it might also prevent or postpone it. Here's what to do:

• Maintain a healthy weight. Losing even a few pounds if you're overweight can reduce blood pressure. Weight loss (achieved through diet and exercise) can sometimes bring hypertension under control without the need for drugs, or with lower doses of drugs.

• Don't smoke. A person with high blood pressure who smokes is at serious risk. Every cigarette raises blood pressure. Quitting lowers it.

• Exercise regularly. Exercise is useful in both preventing and treating hypertension. For one thing, it can help you lose weight. It can also lower your blood pressure somewhat, though it's not understood exactly how this happens. There are other benefits beyond blood pressure reduction: for instance, regular aerobic exercise reduces your risk of heart attack. If you are sedentary and just beginning an exercise program to combat hypertension, remember that you may not see the effects for months. But just 30 minutes of brisk walking four or five times a week can eventually make a difference.

If you already have high blood pressure and plan to exercise intensely, you should first discuss your program with your doctor. Neither exercise nor any other life-style modification is a panacea, however, or a substitute for antihypertensive drugs if these are needed.

• Eat a diet rich in fruits, grains, vegetables, and low-fat dairy products. For details the "DASH" diet.

• Keep your sodium intake low (below 2,400 milligrams daily). There's bitter dispute among scientists and others about this recommendation, but we think it's a good one. There's plenty of evidence that a high sodium intake drives up blood pressure in some people. A high-sodium diet has no advantages and many disadvantages. For instance, the typical salty diet is likely to contain lots of processed foods, be low in vitamins and minerals, and be high in fat. Reducing sodium intake is often an important step in treating high blood pressure.

• If you drink alcohol, do so in moderation: no more than one drink daily for a woman, or two for a man. (A drink is defined as 1.5 ounces of 80-proof spirits, 5 ounces of wine, or 12 ounces of beer, all of which contain the same amount of alcohol.)

What about vitamin supplements?

Researchers at the National Institutes of Health are currently studying the overall effects of diet on hypertension. It's difficult to isolate one nutrient from another and assess the effects that each may have on hypertension. You can't go wrong by increasing your intake of fruits, grains, and vegetables—these may have beneficial effects on blood pressure. Recent studies have shown that as produce intake rises, stroke risk drops.

We recommend vitamin C and vitamin E supplements for their antioxidant potential. It's not clear that they help prevent high blood pressure.

What about calcium, potassium, magnesium supplements?

These three minerals are important in blood pressure regulation. But there's no evidence that high doses of them from supplements will lower blood pressure and help prevent hypertension. Calcium supplements are a good idea for postmenopausal women, but we strongly suggest that you get some calcium and all your potassium and magnesium from foods, which also contain other nutrients you need. Nonfat or low-fat dairy products are the best sources of calcium, though some leafy greens are good, too. You need at least 800 to 1,000 milligrams of calcium daily; women over 50 and men over 65 should get 1,500 milligrams daily. Potassium is plentiful in most foods. Magnesium is plentiful in whole grains, leafy greens, meats, milk, beans, bananas, and nuts.

We've recommended a multivitamin/mineral supplement for many older people (see WELLNESS LETTER, February 1998, or our online Guide to Supplements). If you're on hypertensive medication, your doctor may recommend potassium supplements.

Will taking fish-oil capsules decrease blood pressure?

High doses of fish oil (which contains omega-3 fatty acids) may lower blood pressure on a short-term basis in some people, but are not recommended for preventing or treating high blood pressure. High doses have potential adverse effects, including an increased risk for one type of stroke (see WELLNESS LETTER, March 1999). Moderate doses have no effect on blood pressure.

Can coffee cause high blood pressure?

Any caffeine-containing beverage (tea, cola, or coffee) can temporarily raise blood pressure, especially if you are not used to caffeine. But caffeine is not known to cause hypertension.

How blood pressure is defined

CATEGORY	SYSTOLIC/DIASTOLIC*	RECOMMENDATIONS
Optimal	leass than 120/80	Recheck in 2 years
Normal	less than 130/85	Recheck in 2 years
High-Normal	130-139/85-8	130-139/85-89 Recheck in 1 year; begin life-style modifications; if no change, consider therapy
Hypertension
Stage 1	140-159/90-99	Confirm in 2 months; begin life-style modifications
Stage 2	160-179/100-109	Medical evaluation; begin treatment within one month
Stage 3	180/110 or higher	Medical evaluation; begin treatment within one week

* When systolic and diastolic readings fall into different categories, the higher one is used to classify your blood pressure.

An eating plan to lower blood pressure—the "DASH" diet