Don't have high blood pressure?
Don't assume you never will.
One out of four American adults does. Among people 60 or over, it's one out of two (see "Older
and Higher").
But that doesn't mean everyone else is in the clear.
Say your doctor says that your blood pressure is "high normal," or even "normal." Sounds good,
huh?
Not so good.
Even so-called normal blood pressure raises the risk of heart disease and stroke. What you want
is "optimal" blood pressure (see "What's Your Risk?"). Less than half of all Americans have it ...
and most of them are young.
How can you keep your blood pressure from creeping up from optimal to normal to high?
For years, experts have recommended four proven strategies. The Big Four: cut back on salt; lose
excess weight; exercise; and, if you drink, limit alcoholic beverages to two drinks a day.
Now we can make it the Big Five. A landmark study called DASH -- Dietary Approaches to Stop
Hypertension -- shows that eating the right foods also works. It can lower blood pressure as
much as taking a drug.
Better yet: It's the same diet that may help cut your risk of cancer, heart disease, osteoporosis,
and diabetes.
Designing DASH
For years, researchers were stumped.
"In the 1970s, we found that blood pressures were lower in vegetarians, who eat little or no fat
and cholesterol and lots of fruits, vegetables, and grains rich in potassium, magnesium, and fiber,"
says Frank Sacks, a researcher at Harvard Medical School who helped create the DASH study.
Other studies showed that people who ate more protein also had lower blood pressure. And some
scientists argued that calcium played a role as well.
But when researchers gave people calcium or magnesium supplements, blood pressures barely
budged.
"In the Trials of Hypertension Prevention, the only thing that lowered blood pressure was cutting
back on salt and reducing overweight," says Jeremiah Stamler, professor emeritus at
Northwestern University Medical School in Chicago, who also helped design DASH.
"The scientific literature was confusing," says Lawrence J. Appel, a DASH researcher at Johns
Hopkins University in Baltimore. So they constructed a diet to provide all of the promising
nutrients.
"We decided to test the whole diet, not supplements," says Sacks.
Researchers enrolled 459 adults at four centers around the country. Less than a third already had
hypertension. The rest had normal or high-normal blood pressure -- that is, diastolic pressure
between 80 and 89. ("Diastolic" is the lower of the two blood pressure numbers.)
For eight weeks, people were randomly assigned to one of three diets:
- The "control" diet had levels of fat and cholesterol that matched the average American's diet,
and lower-than-average levels of potassium, magnesium, and calcium.
- The "fruit and vegetable" diet matched the control diet in fat, saturated fat, cholesterol, and
protein. The only difference: Potassium, magnesium, and fiber got a boost when fruits and
vegetables replaced some snacks and sweets.
- The "combination" diet had less total fat, saturated fat, and cholesterol than the fruit and
vegetable diet or the control diet (see "Count the Nutrients"). It was rich in fruits, vegetables,
and low-fat dairy products (which upped the potassium, magnesium, calcium, fiber, and
protein).
"We kept the salt constant in all three diets at 3,000 mg a day," says Appel. (That's slightly less
than the average American's 3,600 to 4,000 mg a day, but more than the 2,400 mg health experts
recommend.) Ditto for other things known to influence blood pressure: Calories were the same
for all three diets (so no one would gain or lose weight) and alcohol was limited to a drink or two
a week.
The researchers didn't have to wait long.
The Winner
"Blood pressure fell within days," says Appel. The fruit and vegetable diet lowered pressure
significantly. But the combination diet won hands down. It lowered average pressures by:
- 3.5 points (systolic) over 2.1 points (diastolic) in those with normal or high-normal blood
pressure, and
- 11.4 points over 5.5 points in those with high blood pressure.
"That's about what you'd get in people given a drug," says Appel.
Why such success when supplements of calcium, magnesium, and other individual nutrients
flopped in earlier studies?
"Maybe you need to eat the nutrients together because the effect of each one is small," says Eva
Obarzanek, a DASH co-author at the National Heart, Lung and Blood Institute in Bethesda,
Maryland. "Or maybe the foods improve the absorption of the nutrients."
It's also possible that something else in fruits, vegetables, and low-fat dairy products lowers blood
pressure. The DASH can't say. Nor can it say which nutrients made the difference.
But it said enough.
"Now we have everything we need to know to end the epidemic rise in blood pressure with age --
and high blood pressure -- in this country," says Jeremiah Stamler.
"We've known how to lower blood cholesterol since 1960. Now we know the same about blood
pressure. So we can prevent both major diet-related risk factors for heart disease and stroke."
DASH-2 is already under way. It will test the combination diet at three levels of sodium intake:
3,450 mg, 2,300 mg, and 1,650 mg a day. "We want to see what bang you get for your buck
when you combine the DASH diet with less salt," says Appel.
And who knows? Maybe someday, someone will compare the DASH diet to those recommended
by Nathan Pritikin and Dean Ornish to see if their advice -- to cut fats and cholesterol even
further, use only whole grains, and add little or no sugar -- yields even greater benefits.
But you needn't wait. Adding the DASH diet to the Big Four (see "The Bottom Line") is easy to
follow, inexpensive, and not too strict.
"The beauty of DASH is that it doesn't take a genius to follow," says Norman Kaplan, a
hypertension expert at the University of Texas Health Sciences Center in Dallas. "You just cut
the fat, double your fruits and vegetables, and use low-fat dairy products."
What's more, the DASH has everything: fruits and vegetables to cut your risk of cancer, calcium
to lower your risk of osteoporosis, and limits on saturated fat and cholesterol to cut your risk of
heart disease.
"It's not a diet for one disease," says Appel. "It's a diet for all diseases."
The DASH "Combination Diet" is low in cholesterol, high in fiber, potassium, calcium, and
magnesium, and moderately high in protein. Here's how it compares with the DASH "Control
Diet," which is closer to what the typical American eats. (Both diets supply 2,000 calories a day.)
