By Peggy J. Noonan
Adjust font size:
Doctors call it "the white-coat effect:" the natural rise in blood pressure that comes with exam-room anxiety. But a simple case of nerves couldn't explain the numbers that Roger Moeller, a 60-year-old editor and publisher in Bethlehem, Connecticut, was hearing during an annual physical.
Since his last visit, his systolic blood pressure -- the force exerted on artery walls with each heartbeat -- had jumped from 130 to 200, while his diastolic pressure -- the force between heartbeats -- rose from 90 to 100, placing him at serious risk for cardiovascular disease.
When his doctor advised exercise and a low-sodium diet in addition to blood pressure -- managing medication, Moeller "heeded the warning," he says. He began walking more than a mile per day and tried to remove excess sodium from his diet. "There are packaged foods you would never think have a lot of sodium in them," he says.
After three months, Moeller's blood pressure reached 150 systolic/90 diastolic an improvement, but still above the 120 systolic/80 diastolic that the National Heart, Lung, and Blood Institute recommends. He learned that he needed to remove even more sodium from his diet.
Grains of Truth
Ironically, sodium plays a vital role in our health. Although no one knows for certain, scientists estimate the body requires 250 to 500 milligrams (mg) each day for basic physiologic functions. "We need salt to transport nutrients, transmit nerve impulses, and contract muscles, including your heart," says Anna Di Rienzo, Ph.D., associate professor of human genetics at the University of Chicago. But when sodium levels are too high, the kidneys release more water, increasing blood volume. With more blood flowing through the body, pressure increases. Over time, a sustained pressure increase causes the heart to work harder to pump blood and threatens the stability of blood vessels, which raises the risk of heart disease and stroke.
This physiological chain of events prompted the experts behind the revised Dietary Guidelines for Americans to reduce the recommendations for sodium intake from 2,400mg per day to an upper limit of 2,300mg for adults. "These recommendations are immensely important for everyone, but especially for those predisposed to develop hypertension [high blood pressure], especially African-Americans, obese people, and those with a family history of hypertension, stroke, or heart disease," says Julius Linn, M.D., member of the Cooking Light advisory board and executive director of medical publications at the University of Alabama at Birmingham. Yet the recommended figure is nearly half what the average American consumes daily, according to the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey.
Though we tend to swap "salt" and "sodium" as if the two words were interchangeable, there is a difference. Table salt is actually sodium chloride, explains Ilene Smith, R.D., M.S., associate director of Ketchum's Food and Nutrition Group. It's 40 percent sodium and 60 percent chloride.
Very little of the sodium we consume arrives in our diets via saltshakers. The majority -- 75 percent -- comes from processed foods, where it enhances flavor, stabilizes, or preserves, Smith says. There are the usual high-sodium sources: bacon, ham, sausage and other cured meats; frozen or boxed entrées; frozen and canned vegetables; fast foods; and sauces and salad dressings. But sodium also hides in unexpected places. For example, cottage cheese can contain almost 1,000 mg per cup. Read labels to find good choices.
The easiest way to avoid consuming too much sodium is to choose fresh, whole foods that are as close to their natural state as possible, says Steve G. Aldana, Ph.D., who is professor of health and human performance at Brigham Young University in Provo, Utah. The reason: Although small amounts of sodium are naturally found in whole foods, they are infinitesimal compared with the amounts found in many processed foods. That doesn't mean you have to forgo convenience in the kitchen, however. Many canned vegetables are available in sodium-free or reduced-sodium versions. Independent of sodium intake, fruit and vegetable consumption also has a positive effect on blood pressure. A diet that is rich in whole, unprocessed foods provides a healthy balance of fiber, vitamins, minerals, and antioxidants. "The closer we get to foods in their natural forms, the better," Aldana says.
One proven eating plan, known as the DASH diet (short for Dietary Approach to Solving Hypertension), leverages the blood pressure-reducing power of whole foods. DASH emphasizes fruits, vegetables, whole grains, and low-fat dairy foods, and limits saturated fat, cholesterol, and sodium. It is the result of a partnership between the National Institutes of Health and the American Heart Association.
When lead researchers from Johns Hopkins University tested the ability of diet to lower blood pressure in 459 people, they found that those who followed the DASH diet for eight weeks reduced their systolic blood pressure by an average of 5.5 points and diastolic pressure by an average of 3 points. Among subjects with diagnosed hypertension, the effects were even more dramatic -- DASH lowered systolic pressure by 11.4 points and diastolic by 5.5 points. (Learn more about DASH and recipes that put its principles into practice) One mineral that plays a key role in the DASH diet is potassium. Found in substantial levels in root vegetables, leafy greens, and fruits, potassium helps balance the effects of sodium in the body. In fact, when the USDA loweredthe dietary guidelines for sodium, it raised the recommendations for potassium from 3,500 to 4,700 mg per day, a figure most of us miss. (Average potassium intakes for women hover between 2,100 to 2,300 mg, while men consume between 2,900 and 3,200 mg.) In a review of 33 clinical trials, researchers from Tulane University Health Science Center in New Orleans, Louisiana, found that increasing intake of potassium-rich foods may lower systolic blood pressure by an average of 3 points and diastolic by 2 points.
Some of us are physiologically sensitive to salt, and thus respond better and faster to a reduction in sodium intake. "Salt-sensitive people will experience a greater reduction in blood pressure than salt-resistant people," Linn says.
Researchers estimate that 10 to 25 percent of the population may be salt-sensitive. Among those with diagnosed hypertension, the number rises to 60 percent.
For now, there's no way to test for salt sensitivity; the best indication may be heredity. To learn more about a possible genetic connection to salt sensitivity, Di Rienzo tested more than 1,000 people from 52 ethnic groups and discovered a variation in a salt-regulating gene called CYP3A5. The gene was most common in natives of sub-Saharan Africa. As the distance from the equator increased, so did subjects' likelihood of a mutation in the gene that causes salt to be retained.
However, experts warn this discovery shouldn't provide license to load up on salt if you aren't sodium sensitive. "While certain traits may tip us off as to who faces the greatest risk from too much dietary sodium, it's difficult to predict who can get away with excess consumption," says Tedd Mitchell, M.D., medical director for the Cooper Wellness Program at the Aerobics Center in Dallas, Texas.
Other factors, such as age, also play a role. Systolic blood pressure rises an average of four points per decade of life naturally, so all adults should reduce the amount of sodium they consume as they age -- regardless of sensitivity levels, Linn says. For people over 50, the 2005 Dietary Guidelines recommend an upper limit of 1,500mg sodium per day. For those over 70, the daily limit drops to 1,200 mg. Simply controlling for the natural rise in blood pressure that occurs over a lifetime could have far-reaching effects.
In a review of data from the INTERSALT study, a research project begun in 1984 to compare sodium intake to rates of blood pressure in more than 10,000 people from around the world, scientists from Northwestern University in Chicago estimated that lowering the average person's sodium intake by a third would cause systolic pressure to drop by an average of five points, and that would correspond to a nine percent lower risk of coronary death and a 14 percent lower risk of stroke death. In a more recent study, the numbers proved even more impressive; when lead researchers from Harvard Medical School limited the sodium intake of more than 4,500 hypertensive men and women to roughly 1,600 mg per day, subjects registered a 26 percent reduction of cardiovascular disease risk after nine to 14 years.
After one year of carefully avoiding excess sodium, Moeller's intake settled to about 1,000 mg per day -- well under the Dietary Guidelines -- and his blood pressure reached the safe zone: 120 systolic/80 diastolic. His skills as a home cook proved invaluable to reaching that figure. In fact, preparing food at home is often the first piece of advice that doctors and nutritionists give patients with high blood pressure. "As head chef in your own kitchen, you can check the nutrition content of foods and choose fresh ingredients," Smith says.
Moeller found that substituting one taste for another -- spicy or sweet instead of salty, for example -- helped him adjust to the change in flavor. He also turned to his spice cabinet for salt substitutes, for example, seasoning cooked vegetables with mint or baked chicken with curry. And instead of toast, eggs, and sausage for breakfast, he ate oatmeal, sweetened with honey or jam.
Walking also helped reduce Moeller's risk. Earlier this year, the American Heart Association moved exercise to the top of its list of lifestyle modifications that can help lower blood pressure; sodium reduction is second. Thanks to the exercise routine, Moeller lost 20 pounds, helping him dodge a second potential diagnosis of prediabetes.
Does Moeller miss the extra sodium? No. "Giving up potato chips was tough, but now I shy away from those kinds of foods automatically," he says. In fact, changing his eating habits has had an unforeseen -- and flavorful -- benefit that has nothing to do with blood pressure: "My diet is much more diverse now," he says. "I look forward to eating."
Peggy J. Noonan is a health and nutrition writer in Denver, Colorado.
The 2005 Dietary Guidelines for Americans recommends a sodium intake of no greater than 2,300mg for adults and 1,200mg for seniors.
BP INCREASES WITH AGE
Did you know?
HOW MUCH IS TOO MUCH?
How Your Daily Sodium Intake Measures Up
SOURCES: USDA Dietary Guidelines for Americans 2005; U.S. Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey
SODIUM LOWDOWNFour easy ways to lower your sodium intake
"Slowly reducing the amount of salt you use will help your taste buds compensate by identifying the other flavors in foods," says Cooking Light's Senior Food Editor, Alison Ashton. We polled the Cooking Light food editors and Test Kitchens professionals for ways to reduce sodium in home cooking without sacrificing flavor. Here are their suggestions:
1. Switch to kosher salt. Because of its larger crystal size, a teaspoon of kosher salt contains almost 25 percent less sodium than ordinary table salt.
2. Subdivide the amount of salt called for in a recipe, then add small portions as you cook and taste as you go. You may need less salt than you think.
3. Minimize the sodium from common pantry staples. Shop for no-salt-added products and read labels to compare sodium levels in processed foods.
4. Use salt where you want the biggest flavor punch. For example, sprinkling salt on top of home-baked bread provides a burst of salty flavor that isn't lost as it would be if incorporated with other components.