1999 Science in Society Journalism Awards

Magazine

Gary Taubes

“The (Political) Science of Salt”

Science

Part Six: Picking your battles

In 1976, when the salt controversy was new, Jean Mayer, then president of Tufts University, called salt "the most dangerous food additive of all." Today the debate has devolved into an argument over whether extreme reductions in salt intake, perhaps impossible to achieve in the general population, can drop blood pressure by as much as 1 or 2 millimeters of mercury, and if so, whether anyone should do anything about it. For people with normal blood pressure, such a benefit is meaningless; for hypertensives, clinicians say that medications have a much greater effect at a cost of a few cents a day. But what works for the individual and what works for public health are still two different things. To Stamler, for instance, or Cutler, there is no question that a population that avoids salt will have less heart disease and strokes. And salt intake, they argue, is far easier to change than, say, smoking or inactivity, because much can be accomplished by convincing industry to put less salt in processed foods.

"As long as there are things in the media that say the salt controversy continues, the [salt interests] win."

— Jeff Cutler

Whether it’s worth it is the question. For the agencies involved to induce the public to avoid salt, they must convince individuals that it’s bad for their individual health, which, for those with normal blood pressure, it almost assuredly isn’t. Although this explains the single-mindedness of the promotional message out of the NHLBI and NHBPEP, it can also make the agencies and administrators look disingenuous. Moreover, public health experts firmly believe that the public can only be sold so many health recommendations. "How much of the government’s moral weight do you expend on this particular issue?" says University of Toronto epidemiologist David Naylor. "You have to pick your battles. Is this a battle worth fighting?" Hammering on the benefits of salt reduction, say Naylor, Hennekens, and others, may come at the expense of advocating weight loss, healthy diets in general, and other steps that are significantly more beneficial.

The argument that salt reduction is a painless route to lower blood pressure also assumes that there is no downside to this kind of social engineering. Social interventions can have unintended consequences, notes NIH’s Harlan, which seemed to be the case, for instance, with the recommendation that the public consume less dietary fat. "It was a startling change to a lot of us," Harlan says, "to see the proportion of fat in the diet go down and weight go up. Obviously it’s not as simple as it once seemed."

The last 5 years have also seen two studies published — the latest this past March in The Lancet — suggesting that low-salt diets can increase mortality. Both studies were done by Michael Alderman, a hypertension specialist at New York City’s Albert Einstein College of Medicine and president of the American Society of Hypertension. Epidemiologists — and Alderman himself — caution against putting too much stock in the studies. "They are yet more association studies," says Swales. "Any insult you make of Intersalt you can make of those as well." But Alderman also notes that only a handful of such studies comparing salt intake to mortality have ever been done, and none have come out definitively negative. "People just rely upon statements that [salt reduction] can’t really do any harm," says Swales. "It may or may not be true. Individual harmful effects can be as small as beneficial effects, and you can’t detect those in clinical trials either."

After publication of his second study, Alderman recruited past and present presidents of hypertension societies and the American Heart Association and wrote to Lenfant at the NHLBI "urging prompt appointment of an independent panel of qualified medical and public health scientists to review existing recommendations [on salt consumption] in light of all available data." In April Lenfant told Science that he had agreed to proceed with the review. If such a panel should convene, Hennekens has one observation worth keeping in mind: "The problem with this field is that people have chosen sides," he says. "What we ought to do is let the science drive the system rather than the opinions."

• Part One: The salt controversy
• Part Two: Crystallizing a debate
• Part Three: Intersalt tries again
• Part Four: Trials and tribulations
• Part Five: Poles apart
• Part Six: Picking your battles
• Part Seven: Touchstones of the salt debate

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