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What Should You Believe About Salt?

A high salt intake and high blood pressure (hypertension) have been linked for many years, not only by scientific research but in the minds of many health-conscious people. However, the furor about trans fat and carbs has moved salt way down on the list of our dietary villains. Only a few people (7%, according to one survey) ever bother to check labels for salt anymore.

As concern has faded, people have been eating more salt. Since the early 1980s, U.S. per capita salt intake has risen by about 50%. In large part, this is because Americans have turned increasingly toward takeout and restaurant meals, fast foods, prepared foods, and snacking. Low-sodium foods don’t sell well. Most packaged foods and restaurant meals are salty—not just at McDonald’s, but also elegant meals on white tablecloths. Portion sizes have increased dramatically, along with the prevalence of obesity and high blood pressure. No connection with salt intake, says the Salt Institute, which looks after the interests of this billion-dollar industry. But we think there is.

The U.S. Dietary Guidelines recommend an upper limit of 2,300 milligrams of sodium daily for young people, and no more than 1,500 milligrams for the middle-aged and older, for blacks (who are more prone to hypertension), and for people who already have hypertension. Table salt is actually 40% sodium and 60% chlorine. A teaspoon of salt contains about 2,300 milligrams of sodium, so 1,500 milligrams is only about two-thirds of a teaspoon. However, Americans consume, on average, about 3,400 milligrams of sodium a day, and many eat much more. Health Canada (the Canadian equivalent of the U.S. FDA) is in favor of limiting salt, too; its upper daily limit is also 2,300 milligrams.

The American Medical Association is campaigning to lower Americans’ salt intake; for example, it wants restaurants and food manufacturers to reduce salt levels voluntarily. It also wants the government to reclassify salt as a food additive so it can be regulated. The Salt Institute is fighting this, claiming health authorities are acting without solid evidence.

One thing is clear: A low-salt diet benefits many people with hypertension. But do other people need to cut back on salt?

What the studies show

Many large observational studies over the years have linked a high sodium intake to high blood pressure and increased deaths from heart attacks and strokes. For example, the Intersalt study looked at 10,000 people in 32 countries and concluded that high salt intake was directly related to hypertension and deaths from stroke. But according to critics, these big population studies do not prove much. Most relied on personal recall—people reported what they thought they ate, which may have been different from what they did eat.

It is much harder to dismiss the research on the DASH (Dietary Approaches to Stop Hypertension) diet, which consists of fruits, vegetables, and whole grains, plus small servings of meat and dairy. It also provides a lot of potassium, magnesium, and other minerals that help control blood pressure. DASH comes in two versions—one with 2,300 milligrams of sodium a day, the other with 1,500. Both diets lower blood pressure in healthy people, but most dramatically in those with hypertension. The lower-sodium version lowers blood pressure even more. If your blood pressure is normal, and you keep your sodium intake moderate, will that prevent hypertension? We have to admit that nobody knows for sure.

But think of this: A new study in Progress in Cardiovascular Diseases from researchers at the University of Helsinki reports that thanks to consistent efforts in Finland, salt consumption has fallen by one-third in thirty years—accompanied by a large de-crease in average blood pressure and a 75 to 80% decrease in deaths from strokes and heart disease. Is the salt decrease responsible? The pro-salt faction would say no, but we think it played a role. If you want to avoid cardiovascular disease, salt reduction is a very good bet.

Advice, and more advice

Here’s what the salt industry advises: There’s no ironclad evidence a high salt intake is bad, so don’t worry. Eat what you want, and enjoy yourself. Help us make a lot of money out of salt.

Here’s our advice: Hypertension and heart disease are highly complex disorders. Nobody has yet pinned down a high salt intake as the chief or only villain. It may turn out that salt is just some kind of fellow-traveler. That is, salty foods like French fries, fast-food sandwiches, pizza, TV dinners, and canned soups are usually also high in calories and "bad" fats and low in nutrients. You get a lot of salt, but not much potassium, magnesium, or other nutrients that help keep blood pressure normal and that constitute healthy eating. What you can achieve by cutting down on salt is a better diet.

Bottom line: Everyone should try to consume no more than 2,300 milligrams of sodium a day. However, if you’re middle-aged or older, black, or have hypertension (blood pressure readings of 140/90 and above), 1,500 milligrams is a better goal. In addition, if you have pre-hypertension (120/80 to 139/89), you should also aim for a maximum of 1,500 milligrams a day. If you don’t know your blood pressure, get it checked.

Fresh fruits, vegetables, whole grains, fish, and meats are naturally low in sodium. You don’t need to add lots of salt. But your salt shaker is the least of your worries. To really cut down on sodium, you’ll need to limit or avoid most processed foods and restaurant meals, or at least choose carefully among them, since they provide about 80% of the sodium consumed in this country. Most people can quickly get used to a lower-sodium diet by using pepper, herbs, spices, lemon juice, garlic, vinegar, and other flavoring agents. After a short time, you’ll begin to appreciate the flavors of foods, and salty things won’t taste as good.

A few tips

• Always read labels. Buy reduced-sodium products.

• Avoid highly processed foods. Pick a plain turkey breast or pork tenderloin rather than one packaged with a marinade or sauce.

• Beware of canned or packaged soups, broths, and stocks.

• Soy sauce, tamari sauce, and most sauces used in Asian cooking are salt bombs.

• Watch out for canned vegetable juices, usually very salty.

• Drain and rinse canned goods, such as beans, to remove most salt.

• If your food is being prepared to order, ask the server to ask the cook not to add salt.

• Reducing portion sizes also reduces sodium intake.

UC Berkeley Wellness Letter, March 2007