Doctors and public health officials have been telling us for years that eating too much sodium can increase the risk of heart attack or stroke by raising blood pressure to unsafe levels. So how to explain a new study that suggests low salt intake actually increases the risk of dying from those causes?
The study, which followed 3,681 healthy European men and women age 60 or younger for about eight years, also found that above-average sodium intake did not appear to up the risk of developing high blood pressure (hypertension) or dying of a heart attack or stroke.
The findings, reported in the May 4 issue of the Journal of the American Medical Association, certainly seem counterintuitive, especially in light of the ongoing public health campaign to lower sodium consumption across the U.S. by urging restaurants and food manufacturers to curtail their use of the ingredient.
In fact, says Jan A. Staessen, M.D., the senior author of the study and the head of the hypertension laboratory at the University of Leuven, in Belgium, the findings “do not support the current recommendations of a generalized and indiscriminate reduction of [sodium] intake at the population level.”
Salt lovers shouldn’t break out their shakers just yet, though. A closer look at the findings shows that they’re not as out of line with the low-sodium mantra as they might seem.
For starters, the participants’ sodium consumption was gauged by measuring the sodium content of their urine over just one 24-hour period at the beginning of the study. Although this method is considered the gold standard for estimating sodium intake, that lone urine test may not provide an accurate snapshot of the participants’ everyday intake over the full eight-year study, as the researchers themselves note.
Even more important, the participants had blood pressure in the normal range at the beginning of the study and were white, relatively young, and slimmer on average than the typical American. Past research has shown, however, that people with hypertension, blacks, older people, and heavier people tend to react more negatively to sodium.
“Maybe it would be better to pinpoint specific subgroups,” says Jerome Fleg, M.D., a medical officer in the division of cardiovascular sciences at the National Heart, Lung and Blood Institute, in Bethesda, Md. “This is probably not the group that would get the biggest bang for the buck in terms of restricting sodium intake.”
Staessen and his colleagues divided the study participants into thirds according to their estimated sodium intake. Although higher salt intake was not linked to an increased risk of hypertension, it was associated with very small increases in systolic blood pressure (the top number).
Slightly more than 6 percent of the participants had a heart attack, stroke, or other cardiovascular emergency during the study, roughly one-third of which were fatal. Those who consumed the least salt had a 56 percent higher risk of death from a heart attack or stroke compared with those who had the highest consumption, even after controlling for obesity, cholesterol, smoking, diabetes, and other risk factors.
The researchers don’t have a firm explanation for this finding, but they speculate that sodium intake low enough to decrease blood pressure may also decrease sensitivity to insulin, encourage a stress response in the nervous system, and affect hormones that regulate blood pressure and sodium absorption. “Each of these effects might have unfavorable impact on cardiovascular mortality,” Staessen says.
He and his coauthors emphasize, however, that people with hypertension-who were not included in the study-will still benefit from a low-salt diet.
Most Americans consume more sodium per day than is considered healthy. Federal guidelines recommend limiting consumption to 2,300 milligrams per day, or 1,500 milligrams for blacks and people with hypertension. Some health organizations have been lobbying the federal government to drop the goal for everyone to 1,500 milligrams a day, Fleg says. First, you need to become aware of the many types of sodium (more on that later) and then rid your shelves of foods that are not healthy for you. Everyone knows ballpark favorites like potato chips and hot dogs are off limits, same with other highly processed foods. However, nutritious foods like cottage cheese, peanut butter and canned green beans are teeming with sodium. Olives, salad dressings, anchovies and artificial seafood can turn a well-intended salad bowl into a sodium dumpsite.
Craving the zing of sodium is an acquired preference that can be unlearned. The National Institutes of Health and the American Heart Association recommend no more than 2,400 milligrams of sodium, or one teaspoon of salt, per day. As a person with hypertension, you must learn how to use herbs and spices, create your own low sodium flavor blends and develop some sodium smarts. Practice at least one of these tactics each week and watch your taste buds change:
- Read labels: Disodium phosphate, monosodium glutamate (MSG), sodium benzoate, sodium hydroxide, sodium nitrite, sodium propionate, sodium bicarbonate (baking soda) and sodium sulfite are all forms of sodium that have as much effect as table salt (sodium chloride), so limit foods that contain them.
- Don’t use raw salt: Adding salt at the table is a no-no, as is salting water for cooking rice and pasta.
- Limit sauces and soups: Soy sauce, teriyaki sauce, prepared mustard, canned vegetables and canned soups are brimming with sodium and should be replaced with their reduced sodium alternatives (watch them too as reduced sodium does not mean low sodium).
- Know your frozen foods: Microwavable foods are often full of sodium. Instead opt for plain frozen fruits and vegetables that are packaged as is.
- Read menus with care: Be aware that pickled, smoked and au jus are all chef-speak for sodium, just like anything “in broth.”
- Be mindful of sodium substitutes: Watch out for sodium substitutes as they are high in potassium and can mean trouble if you have kidney problems. Beware of garlic salt, onion salt and even lemon pepper as they can all have high amounts of sodium.
- Marinate meats: Use lime and lemon juice to flavor meats and get a mouth-watering effect similar to sodium.
The Dietary Approaches to Stop Hypertension Eating Plan is an excellent map to get you on the right road. The DASH Eating Plan is high in potassium, calcium and magnesium, nutrients that counteract the impact of sodium in your body and help reduce your blood pressure. (They can also prevent you from developing hypertension if you don’t have it.) The DASH plan focuses on eating more fruits, vegetables, whole grains as well as low-fat dairy-all foods that have low amounts of added sodium. It also keeps your intake of lean beef, pork, poultry and fish to only two servings a day.
Be sure to include more physical activity in your routine, too. If you have hypertension, limit your intake of alcohol to one drink per day. And when you eat an occasional high sodium food, it is even more important to DASH to low sodium fruits, vegetables and whole grains for the rest of the day.
Don’t let high blood pressure take years off your life. Restrict processed and other high-sodium foods to a tiny corner of your pantry, and use the new wide open space to stock up on food that’s good for you. Your taste buds will perk up, and your health risks will go down.