That lovin' spoonful
Salt is poison
Salty history
Intersalt assault
Big study. Big problems?
Millimeters of megadeath
Finding common ground

By one count, 35 percent of the American population should control salt

DATA: courtesy Dr. Clarence Grim, Medical College of Wisconsin

Crystal death?
A low-salt diet is a key to better health, and salt -- mainly from processed foods, helped by the old salt shaker -- is killing us, says the NHLBI and an influential wing of scientists who study hypertension, or high blood pressure.

"The preponderance of the evidence indicates that there's a relationship between salt and blood pressure," says Edward Rocella, coordinator of the National Blood Pressure Education Program at the NHLBI. That was the message from a January, 1999 meeting sponsored by NIHLB and published in LINK April 2000 Hypertension.

Who should restrict salt intake?
-60 percent of hypertensives = 36 million

-children of hypertensives = 36 million

-patients with heart failure = 6 million

-kidney disease = 6 million

-diabetics = 10 million

-TOTAL = 94 million

The meeting was called to respond to some of the criticism we'll be covering. [Following three sentences updated Dec. 27, 2005]. Our bodies need about 500 milligrams of sodium per day, Rocella says, equivalent to 1250 milligrams of salt, yet Americans average 3,375 milligrams , according to the 1999-2000 National Health and Nutrition Examination Survey. In 2004, the U.S. National Academies issued a report calling for maximum sodium intake of 2,300 milligrams, which comes to 5.8 grams of salt per day. 95 percent of American men, and 75 percent of women, take in more than that each day.

By cutting down on salt, according to this argument, millions of Americans would live longer, healthier lives. Heart attacks would decline, likewise strokes. We'd even see a reduction in deadly kidney diseases, since the delicate blood vessels in the kidney are damaged by high pressure, leading the blood to fill with junk chemicals.

Blood pressure is measured by two numbers: The first, called "systolic," measures pressure in the artery while the heart pumps. The second, or "diastolic," measures pressure between beats. The numbers are listed as "systolic/diastolic," pronounced, "120 over 65." Hypertension is usually defined as a sustained pressure above 140/90.

More evidence for a relationship between salt and hypertension comes from research by Denton, who fed chimpanzees a low-salt diet for a year, then raised the salt level in half of them for another year, until they were getting 12 grams of salt per day, as much as a human salt freak. Systolic blood pressure rose 33 millimeters, he says, and diastolic, about 10. Once the salt was withdrawn, the pressures moderated into the normal range. "It was quite a striking indication of a specific role for salt in blood pressure in these animals," says Denton, who observes that chimps are our closest relatives.

High-pressure headaches
Continuous high blood pressure causes disease by stressing the entire cardiovascular system:

The heart must work too hard, causing its muscle to expand and eventually get weak and flabby.

High pressure causes tiny breaks in arteries, and the natural repair process accelerates hardening of the arteries, which can impair blood circulation or cause strokes, complete blockages that starve the brain of oxygen.

Poor blood circulation can damage the eye, kidney, brain and other critical tissues.

Obese people are particularly likely to have hypertension, because each pound of fat must be served by miles of tiny arteries, all of which increases the pressure by raising resistance to the heart's pumping. Ditto for the elderly, whose arteries are already damaged by other effects of aging.

Despite the public-health obsession with sodium, the system that regulates blood pressure depends on many other factors, including other nutrients, genetics, hormones and the environment. Curiously enough, while high sodium concentrations do raise blood pressure in many people, they can also have the opposite effect. And that's only one reason salt studies are repeatedly shaken up by new interpretations of the data.

How long has this been going on?