The Salt Institute has long extolled "performance-based" policies. For roadways, "performance management" means policy driven by outcomes measured in terms of safety and reliability in moving people and goods from point A to point B. For dietary salt, we've called for "performance-based" policies driven by health outcomes: a person's salt intake should be driven by the health consequences of that person's dietary salt intake. The goal is safe, reliable and efficient roads and longer, healthier lives.

University of California-Berkeley law professor Stephen D. Sugarman authored an op ed piece in today's San Francisco Chronicle urging what he termed "performance-based regulation" of dietary salt intake. He called for a "cap and trade" system as has been widely debated as a means of curbing America's carbon emissions.

Sugarman should stick with law. He clearly doesn't understand physiology, economics or history.

His argument goes off-track early when he posits that consumers are helpless victims of food processors. To him, consumers are unable to determine how much salt they're eating despite widespread use of nutrition labels. Since a major portion of the salt Americans ingest comes from processed foods, the clear answer for Sugarman is to regulate salt consumption by "imposing financial penalties" on food manufacturers. Specifically, "we could demand that large retailers cut the total amount of salt in food they sell." Retailers like Wal-Mart would then demand "its food providers to reduce the salt they add to their products, reducing the volume of salty products it sells (by raising the price, providing smaller or less attractive shelf space), introducing and promoting less-salty or salt-free alternatives, given Wal-Mart customers more information about the salt they're consuming, and more." Trouble is: that's hardly creative. That's what's happening now here in North America and in the UK. And it's not working.

Food procesors have used a "stealth" approach to paring back the salt content of food products. They put their salt alternative products at eye level on grocery shelves and relegate "round cans" to shoetop shelves. They've introduced an enormous array of "low-salt" or "salt free" products. They've provided consumer education materials going far beyond federally-mandated nutrition labels. And they've watched as salt intake continues unabated.

The problem lies not with the food manufacturers, but with the customers. And customers "know" they want to cut back on salt. Some assiduously count milligrams of sodium towards a target based on a "daily reference value." To no avail. Why not? Physiology. Economics. History.

Human salt intakes are unchanged over the past century. When humans have access to salt, they consume it in a predictable and fairly narrow range of about 2,300 - 4,600 milligrams sodium a day. We know this because for many years medical scientists have studied various health concerns and routinely extracted 24-hour urine specimens. Those numbers and unchanged over many decades. Nor are humans unique: livestock and poultry, like humans, need salt to live and each species has developed its own predictable, narrow range of intakes -- the phenomenon is well understood by animal nutritionists.

Why it should be so has been more elusive, but even that conundrum is yielding to scientific assault. A February 2008 Experimental Physiology article on "Central regulation of sodium appetite " explains how our brains control salt intake. Appetite is what counts. Not taste. Not politically-correct menu choices. Not even the cost or quantity of the food. Americans eat a diet far less dense in sodium compared to calories than they used to -- perhaps because consumers have the tools and the motivation to try to reduce salt. They just cannot behaviorally control a hard-wired, neurally-mediated appetite. Sugarman suggests food manufacturers and retailers can "reduce the flow of slat in ways that best satisfy consumer preferences." But all "preferences" are not conscious choices. Salt appetite is not a conscious consumer choice.

Thus, the economics is all wrong. "Demand" is not elastic at all. It's fixed. You can reduce the amount of salt per serving and all that you'll produce is consumption of more servings. Taxing Wal-Mart for the amount of salt it sells would be impossible to control; would you have Wal-Mart tell its customers to buy their food elsewhere because they had used up their allotment?

And history gives no comfort either. Recognizing this inelasticity of demand -- the physiologic requirement expressed as salt appetite -- many countries throughout history have monopolized the salt trade and taxed it heavily. The French gabelle triggered the bloody French Revolution. China's imperial salt tax funded much of the country's rule, from dynasty to dynasty. India won independence in no small part based on Gandhi's adroit exploitation of indefensible British "protection" of salt production.

Sugarman admits he has no idea how much cutting salt would lower blood pressure. Of course, that's the wrong question. If he's interested in "performance" it's not blood pressure by health outcomes he should be championing. He says he seeks "a big step in a healthier direction, and performance-based regulation is the most promising way to get there."

We agree, Mr. Sugarman, but you need to learn a bit more about what performance really means. A performance-based intervention would improve health. Salt reduction won't.