Is Salt Bad? A Prison Study May Hold the Answer

There is a lot to fight over in the vagaries of dietary science, but possibly nothing has been as contentious or as longstanding as the salt wars. For decades, public-health officials have pushed people to eat less salt, which is linked to lower blood pressure, which in turn is linked to less heart disease. And for the same decades, a vocal opposition has challenged the guidelines as unscientific: No solid evidence directly links salt intake to heart disease over the long term.

In May 2017, Daniel Jones, an obesity researcher at the University of Mississippi Medical Center, convened a group on both sides of the salt debate to explore the feasibility of a randomized controlled trial. “Over the last few years in the medical literature,” he said, “there has been … ” He paused to look for the right words. “I’ll say, a more contentious spirit. It was bothersome to me to see people disagreeing in a disagreeable way.” Jones himself believes current data sufficiently supports a link between salt and heart disease, but he thinks stronger evidence in the form a randomized controlled trial could provide the push for policies that limit salt in processed foods.

The groups ran through their research options. The best evidence linking salt intake and high-blood pressure comes from short-term feeding studies, where researchers prepare the meals for participants over several weeks. But it is far too expensive to feed participants for the years it takes for heart disease to show up. And frankly, how many volunteers would follow a bland diet for years?

So they considered people already on controlled diets. Nursing homes, they ruled out because many of the elderly have medical conditions that already require eating a certain amount of salt. The military they ruled out because the population is so young and fit that it would take too long for heart disease to show up. That left prisons.

A Prison Study

The Department of Health and Human Services currently restricts federally funded research in prisons to five categories: 1) studying incarceration or criminal behavior itself, 2) studying prisons as institutions, 3) studying conditions that disproportionately affect prisoners like drug addiction or hepatitis, 4) epidemiology research on prevalence and risk factors of disease, and 5) research that can help the prisoners being studied.

The pilot study will be privately funded, he says, but they hope to seek federal funding for a larger study at several different prison sites, ideally federal prisons for the sake of standardization. Each site will be randomly assigned to feed inmates either their current diet or a low-sodium diet of less than 2,300 milligrams per day, as recommended by the American Heart Association. Individual prisoners will not choose the menu they’re offered—the rationale being they already do not have control over prison menus, says Jones—but they can decide whether they want their health data to be collected for the study.

But is it, in fact, okay to take salt away from an entire prison and serve food that most people would think is bland, if healthy? (The average American eats 3,400 milligrams of sodium per day.) Unappetizing food—like the nutritionally complete but tasteless nutraloaf—has been used as a form of punishment in prisons. Howard suggested the prisoners who object to a low-sodium diet, either because of health or matters of taste, be given a way to opt out.

But that could cause logistical complications. There is no way to monitor exactly what prisoners are eating, only what they are being offered. “People share their food. They dump their food trays,” says Aaron Littman, a lawyer at the Southern Center of Human Rights. “It’s not like somebody is watching your intake.” Prison food is also notoriously bad, and many prisoners supplement their diets with food bought from the commissary—most of it high-sodium snack foods like ramen or chips. Jones says one goal of the pilot study is to figure out how much of the prisoners’ diets is coming from the commissary, and they may work with vendors to restrict the sale of high-sodium foods.

Reiter notes that even the best-run studies in prison rest on a fundamental premise: “Scientists need some kind of controlled environment and population. They’re partly exploiting the institutional circumstances.” Federally funded biomedical research in prisons is now rare because of the HHS restrictions. But pharmaceutical companies can also run privately funded trials in prisons—as they have done on HIV drugs in Florida, Texas, and Rhode Island—and they are not legally bound by the same regulations. “I think it’s a Pandora’s box,” says Reiter, and the opaqueness of the prison system makes it hard for abuses to come to light.

Prisoners are also not entirely representative of the general population, which could make it harder to generalize from their data. They are disproportionately male and people of color. They have higher rates of drug use, HIV, and hepatitis C. They are not an ideal population for a health study, but they may be the only one available—that is, if they should be available for research at all.

Jones says he’s been getting feedback from the scientific community—most of it encouraging—since publishing the proposal. He’s also hoping to engage more ethicists and prisoners’-rights advocates. “Broadly, we’re looking for advice on whether this is an insane idea,” he says. “Or whether it’s something that experienced people think might be achievable.”


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