March 2010

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The Salty Stuff

Salt, Blood Pressure and Your Health

Salt is essential to our body’s fluids. That’s likely why we evolved to enjoy its taste. On the other hand, anyone who’s gotten a mouth full of seawater knows that too much salt tastes terrible. Maybe your body’s trying to tell you something. It turns out that too much salt can lead to a host of health problems.

The chemical name for dietary salt, or table salt, is sodium chloride. Since 90% of the sodium we ingest is from salt, it’s difficult to separate the effects of salt and sodium in many studies. However, it’s the sodium part most doctors focus on.

“The best known effect of sodium on health is the relationship between sodium and blood pressure,” explains Dr. Catherine Loria of NIH’s National Heart, Lung and Blood Institute (NHLBI). Dozens of studies, in both animals and people, have shown that a higher salt intake raises blood pressure. Reducing salt intake, on the other hand, lowers blood pressure.

Blood pressure is the force of blood pushing against the walls of The vessels that carry blood from your heart throughout your body. arteries as the heart pumps out blood. When this pressure rises—a condition called high blood pressure, or hypertension—it can damage the body in many ways over time. High blood pressure has been linked to heart disease, When normal blood flow to the brain is stopped, usually by ruptured or blocked blood vessels. stroke, kidney failure and other health problems.

There are 2 blood pressure numbers, and they’re usually written with one above or before the other. Systolic, the first, is the pressure when the heart beats, pumping blood through the arteries. Diastolic is the pressure when the heart is at rest between beats. The numbers 120/80 mmHg are the ones you should aim to keep your blood pressure below.

Some research also suggests that excessive salt intake might increase the risk of stomach cancer. Scientists continue to investigate this possible connection.

Researchers do know that not everyone is equally sensitive to salt. “From our experiments, we know there’s lots of variation in the blood pressure response,” Loria says. Certain groups of people see greater reductions in blood pressure when they lower their salt intake: African-Americans, older people and people with blood pressure above normal.

“Within those groups, there’s a lot of variation between people.” Loria says. But about 1 in 3 adults nationwide has high blood pressure right now. Another third have “prehypertension,” meaning their blood pressure numbers are high enough to put them at risk to develop high blood pressure. In light of this, she says, “it’s really important for the majority of the population to reduce their blood pressure.”

Experts recommend that people take in less than 2,400 milligrams of sodium a day—that’s what’s in about 6 grams of salt, or about a teaspoon. People with high blood pressure should shoot for 1,500 milligrams or less—about 3.7 grams of salt. But right now, the average man in the United States takes in over 10 grams of salt per day and the average woman over 7.

Dr. Kirsten Bibbins-Domingo at the University of California, San Francisco, recently led an NIH-funded study that used computer modeling to explore the effects of a modest reduction in salt intake in the United States. The researchers found that reducing salt intake by 3 grams per day could cut the number of new cases of heart disease each year by as many as 120,000, stroke by 66,000 and heart attack by nearly 100,000. It could also prevent up to 92,000 deaths each year. All segments of the population would benefit, with African-Americans having the greatest improvements overall. Women would particularly benefit from reductions in stroke, older adults from a decline in heart disease and younger adults from fewer deaths.

Some countries have already begun to tackle this problem using various strategies, such as working with industry to reduce the salt content in processed foods, requiring labels on ready-to-eat foods and educating the public. The UK has achieved a 10% reduction in salt consumption over the past 4 years.

But wouldn’t we all miss the taste? “Several studies have shown that as you gradually reduce sodium intake, you lessen your desire for salty food,” Loria says. And surveys of people across the UK have found that most people didn’t notice any difference in the taste of their food.

“A very modest decrease in the amount of salt, hardly detectable in the taste of food, can have dramatic health benefits for the U.S.,” Bibbins-Domingo stresses.

The salt we sprinkle on our food actually accounts for less than 10% of our salt consumption. Most of the salt we eat salt comes in processed foods from stores, restaurants and dining halls. You may already know that fast food, cold cuts and canned foods tend to have a lot of salt.

“Many people don’t realize that a lot of our salt is from breads and cereals,” Bibbins-Domingo says. Studies have found that over 20% of the salt in the average American’s diet comes from grain products, such as breads, cereals, crackers and chips.

“In terms of advice, I think the best guidance we have is for people to pay attention to nutrition facts on the labels,” Loria says. “The percent daily value is a better guide than the language that’s used on food labels like ‘low-salt.’ These labels can be confusing because they have very defined technical meanings.” Try to select foods, she advises, with less than 5% of the daily value of salt per serving.

Even small reductions can have an effect on your blood pressure. If you can’t find a low-salt alternative to a particular food, it still helps to pick something that’s lower than what you’re already consuming. “You can find remarkable variation in the amount of salt across major brands of food,” Bibbins-Domingo says. “Even without choosing something labeled ‘low sodium,’ you can often find a lower sodium alternative.”

Beyond salt, a healthy eating plan can help keep your blood pressure under control. Check out NHLBI’s Dietary Approaches to Stop Hypertension (DASH) eating plan at Other lifestyle measures can help you keep your blood pressure down, too. Lose weight if you’re overweight or obese. Get regular physical activity. Quit smoking. And manage your stress. The more of these steps you take, the more likely you’ll be to avoid related health problems.

Why not start now? Make small changes at first, and then keep working to gradually lower your family’s salt intake.

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