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Research: Curbing salt intake could add years to your life

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Potato chips. Pretzels. Pizza. French fries.

Thoughts of these foods can make our tongues dance as we anticipate satisfying our salty cravings.

There's just one problem: The amount of sodium people consume from these and other processed foods is more than what is considered healthy. What's more, cutting back on salt in the processed foods we eat could help us live for many more years -- even if we are healthy.

"The Western diet is way too high in sodium. ... People eat way too much, and it increases your risk for cardiovascular disease, stroke and stomach cancer," said Sonya Angelone, a registered dietitian who specializes in cardiovascular nutrition and is the media spokeswoman for the Academy of Nutrition and Dietetics. Research also suggests that too much salt can negatively affect bone health in young girls and postmenopausal women.

A 'salty' condiment

Angelone, who previously chaired the nutrition committee for the American Heart Association's San Francisco chapter, said that excess salt is harmful to the cardiovascular system in two ways.

For one, though its effects vary among individuals, too much sodium can raise blood pressure. "Some (people) are sodium-sensitive and can't eat more than 1,500 milligrams per day (equivalent to less than three-fourths teaspoon of salt), or their blood pressure will go up," she said.

But even if you are not sensitive to sodium and are generally healthy, you may still be putting your health at risk by consuming excess salt.

"A high sodium intake can damage the natural ability of blood vessels to dilate and increase blood flow to tissues," said Dr. Frank Sacks, professor of cardiovascular disease prevention in the Department of Nutrition at the Harvard T.H. Chan School of Public Health.

"It boils down to having a healthy endothelial lining -- a one-cell-lined-thick layer that lines your arteries," Angelone explained. "Too much sodium stiffens cells that line arteries and keeps them from releasing nitric oxide, which keeps arteries flexible."

In fact, the more sodium we consume, the greater the risk of heart disease. According to one recent study published in the journal Circulation, for every 1,000 milligram increase in sodium intake, the risk of cardiovascular disease increases by 17%.

Some people may experience bloating when consuming too much salt, which can contribute to bags under your eyes, puffiness in your face and swelling in your fingers.

"If you consume a lot of sodium, your rings might get tight," Angelone said. That's because sodium acts like a sponge in the body, absorbing fluid. "The more salt in your diet, the more fluid and the more volume of blood your heart has to pump through your arteries."

Sodium recommendations

According to the American Heart Association, our bodies need only a small amount of sodium -- less than 500 milligrams per day, about the equivalent of the sodium in a half-cup of chicken broth -- in order to function properly. Yet most of us consume about seven times that: more than 3,400 milligrams of daily sodium, the equivalent of more than 1.5 teaspoons of salt per day, or the amount in almost four tablespoons of regular soy sauce.

The most recent US government dietary guidelines recommend that all individuals limit sodium intake to 2,300 milligrams per day, or the amount in about one teaspoon of salt.

A limit of 1,500 milligrams per day is no longer recommended for high-risk groups including those with heart disease, kidney disease and diabetes, according to a recent report from the Institute of Medicine, as "evidence of both benefit and harm is not strong enough to indicate these subgroups be treated differently from the general US population," explained committee chairman Dr. Brian Strom.

Yet the more recently published Circulation study found a progressive decline in cardiovascular disease events among those with lowered sodium levels -- even as low as 1,500 milligrams. In fact, the American Heart Association still recommends a limit of no more than 1,500 milligrams of sodium per day for most adults.

"Several trials clearly demonstrated that lower sodium intake down to 1,500 milligrams decreases blood pressure more than lowering sodium to 2,500 to 3,000 milligrams," said Sacks, who is also on the American Heart Association's sodium reduction task force and is an association spokesman. "This is especially important in people who have higher risk of heart attacks and strokes, those who are over 60 years old and those with hypertension."

Though recent research has suggested that very low levels of sodium might cause harm, "those studies which purport harm at low levels of intake are fundamentally flawed," said Dr. Lawrence J. Appel, who authored the Circulation study and is director of the Welch Center for Prevention, Epidemiology, and Clinical Research at the Johns Hopkins Medical Institutions. "Most of these papers use single 'spot' collections of urine from a single void, which do not represent usual intake over the long-term."

If achieving current recommendations for sodium intake is not enough motivation for the food industry to police itself, the findings of a study published this month in the journal PLOS Medicine might be. The study found that adherence to the FDA's targets "would prevent 450,000 cases of cardiovascular disease and 83,000 deaths over a 20-year period," according to study author Jonathan Pearson-Stuttard of Imperial College London.

That's a lot of sodium to slash.