How does salt affect blood pressure?

DEAR DOCTOR K:

I have high blood pressure, and my doctor advised me to cut back on salt. Can you explain how salt affects blood pressure?

DEAR READER:

Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps blood. High blood pressure, also known as hypertension, is blood pressure greater than 140/90 mm Hg. High blood pressure increases your risk of stroke, heart attack, kidney damage, loss of vision and other health problems. Many studies show that blood pressure rises with higher levels of sodium in the diet.

Salt — sodium chloride — is essential for survival. But when you take in more sodium than your body needs, your body holds on to water to dilute the sodium. As a result, the amount of fluid in your blood vessels increases. That raises the pressure inside your blood vessels, and it makes the heart work harder.

Research has shown that higher salt intake is linked to increased risk of strokes and heart disease. And the landmark DASH-Sodium trial showed that cutting back on salt lowers blood pressure. (The DASH diet was developed by nutritionists to lower blood pressure. Key features include plenty of fruits, vegetables and whole grains; several servings daily of low-fat dairy products; some fish, poultry, dried beans, nuts and seeds; and minimal red meat, sweets and sugar-laden beverages.)

But does cutting back on salt save lives? Yes, it does. Several studies have shown that lowering dietary sodium leads to fewer deaths from heart attacks, strokes and other cardiovascular events.

So what should you do? If you’re the “average person” in the United States, you should reduce your daily sodium intake. The U.S. Centers for Disease Control and Prevention (CDC) reports that the average person consumes 3,436 milligrams of sodium each day. In contrast, the CDC recommends that no one consume more than 2,300 milligrams (about a teaspoon of salt) per day.

However, if you are 51 years of age or older, or if you are an African-American of any age, or if you have high blood pressure or diabetes or kidney disease, you should consume no more than 1,500 milligrams of sodium per day. That covers the majority of adults in the U.S.

Start by paying attention to how much sodium is in the foods you eat. You can find this information on food labels. (I’ve put a table showing the top 10 food sources of sodium in the American diet below. Avoid these foods, or at least go light on them.)

Watch out for hidden sodium, too. Some foods that are high in sodium may not taste especially salty. Examples include breakfast cereals, bakery muffins, energy and sports drinks.

Also pay attention to potassium. In contrast to sodium, more potassium in your diet helps keep blood pressure in check. Many fruits and vegetables, like bananas, oranges and grapefruit, are naturally low in sodium and are good sources of potassium. The CDC recommends that people consume 4,700 milligrams of potassium each day from food (not supplements).

Where’s the salt?

Salt plays many roles in food, from acting as a preservative or a binder to helping yeast rise. It is also a cheap way to make food tastier. Here are the top 10 food sources of sodium in the American diet, based both on sodium content and how often people eat these foods. Cutting 25% of the sodium from these 10 food categories would lower the average American’s sodium intake by 360 mg. That decrease could prevent nearly 28,000 deaths and save $7 billion in health care costs each year, according to estimates from the Centers for Disease Control and Prevention.

  1. Breads and rolls
  2. Cold cuts /cured meats
  3. Pizza
  4. Poultry (fresh and processed)
  5. Soups
  6. 6. Sandwiches (including burgers)
  7. Cheese
  8. Pasta mixed dishes (e.g., spaghetti with meat sauce)
  9. Meat mixed dishes (e.g., meat loaf with tomato sauce)
  10. Savory snacks (e.g., chips and pretzels)

Source: Centers for Disease Control and Prevention.