The Sneaky Side of Salt
University of California Berkeley Wellness Letter
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 (seven percent, 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 percent. 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 those of African decent (who are more prone to hypertension), and for people who already have hypertension. Table salt is actually 40 percent sodium and 60 percent 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.