Salt: coincidence or conspiracy?

"The past few months have provided an especially rick flow of confusing--and often contradictory--discoveries," said the New York Times last March. An example:

"Earlier this month, a study said low-salt diets might be dangerous. Five days later, another said they're great, lowering high blood pressure enough to help elderly people get off medication." It was confusing, all right...because neither the Times nor most other media outlets bothered to look closely at the studies. One was flawless. The other was junk science.

But confusion may be part of someone's game plan. This isn't the first time a shoddy study on salt and hypertension hit the press the same week as a major well-designed study.

Coincidence?

Flawless

Older than 60? Chances are you have high blood pressure. And chances are it's not under control ... which means a higher risk of heart disease, stroke, and kidney failure.

Cutting salt and excess weight can lower your pressure, says a new study called the Trial of Nonpharmacologic Interventions in the Elderly (TONE).

For roughly three years, researchers studied 875 men and women aged 60 to 80 whose blood pressures were lower than 145 (systolic) over 85 (diastolic) while taking a drug that lowers blood pressure.

Each person was randomly assigned to one of four groups. Three of the four attended meetings where they learned to cut sodium intake to no more than 1,800 mg a day, to lose at least ten pounds (if obese), or to do both. People in the fourth group were told to follow their doctors' advice on lowering blood pressure ("usual care").

After three months, the researchers were able to take most of the participants off their bloodpressure-lowering drugs. Then they kept track of how many had a relapse--that is, high blood pressure in a follow-up visit, a return to medication, or a cardiovascular "event" like a heart attack, stroke, coronary bypass surgery, or angioplasty.

People who cut sodium were 31 percent less likely to relapse than those who didn't. And compared to obese people who got usual care, the likelihood of a relapse was:

* 40 percent lower in obese people who cut sodium,

* 36 percent lower in obese people who lost weight, and

* 53 percent lower in obese people who did both.

"The study shows that if older people cut back on sodium and lose excess weight, they may be able to stay off blood-pressure-lowering drugs," says co-author Paul Whelton of Tulane University in New Orleans.

Junk Science

Researchers at the Albert Einstein College of Medicine in New York--including Michael Alderman, a former consultant to the industry's Salt Institute--studied the diets that 11,346 people reported eating during a 24-hour period in the early 1970s.

Then they compared the sodium intakes of the 3,923 participants who died over the next two decades with the intakes of the survivors.

The death rate was slightly higher among people who reported eating the least sodium. But the study was riddled with flaws:

* The low-sodium-eaters were more likely to have high blood pressure, which would have raised their risk of dying (and might explain why they ate less salt).

* The low-sodium-eaters also reported eating an implausibly low number of calories--fewer than 1,000 a day for the average woman--but they weighed no less. That means the group was "contaminated" with people who didn't--or couldn't--comply with instructions to report everything they ate. Non-compliers typically have a higher risk of dying.

* When the researchers "adjusted" for the low calorie intake by looking at how much salt people were eating for each 1,000 calories, heavy sodium users had a higher risk of dying (as one would expect).

"No good researcher would even publish the unadjusted data," says Lawrence Appel of Johns Hopkins University in Baltimore.

"I don't know how this study got published. It's outrageous."

Lancet 357: 781, 1998.