The Ideal Subjects for a Salt Study? Maybe Prisoners.
Posted June 4, 2018 6:35 p.m. EDT
Suppose you wanted to do a study of diet and nutrition, with thousands of participants randomly assigned to follow one meal plan or another for years as their health was monitored?
In the real world, studies like these are nearly impossible. That is why there remain so many unanswered questions about what is best for people to eat. And one of the biggest of those mysteries concerns salt and its relationship to health.
But now a group of eminent researchers has suggested a way to resolve science’s so-called salt wars. The researchers want to conduct an immense trial of salt intake with inmates, whose diets could be controlled.
The researchers, who recently proposed the idea in the journal Hypertension, say they are optimistic it will happen.
Using inmates as study subjects is controversial, to say the least. History is laden with horror stories. In the 1940s, prisoners were deliberately infected with malaria. In the 1950s, inmates were infected with hepatitis. A decade later, scientists irradiated prisoners’ testicles.
“Prisons are an inherently coercive environment,” said Ruth Macklin, an ethicist and professor of epidemiology and population health at Albert Einstein College of Medicine. But “that doesn’t mean informed consent is impossible.”
The point of the proposed study is to put an end to decades of scientific disagreement over salt and its benefits and hazards.
On one side are researchers who say Americans eat too much sodium and that it is harming their health.
For healthy people, the American Heart Association recommends 2,300 milligrams a day. But for those with high blood pressure, the ideal amount is 1,500 milligrams, or less than half a teaspoon.
The higher one’s blood pressure, the greater the risk of heart attacks and strokes. Low-salt diets lower blood pressure, so a very low-salt diet should result in less cardiovascular disease and fewer deaths.
On the other side are scientific dissenters who say, “Prove it.” They worry that very low sodium levels can make health worse, citing studies that found higher death rates and rates of heart attacks and strokes in people following low-sodium diets. And the stubborn resistance of people told to consume less salt indicates to some experts that humans crave salt for a reason — they need it for their health.
Average sodium consumption in the United States and in many other countries has not budged for decades. It is about 3,200 milligrams a day.
For years, medical experts, including a group that produced a report for the Institute of Medicine on dietary sodium, have called for a randomized clinical trial of sodium in the diet that looked at outcomes like deaths and strokes, not at risk factors like blood pressure.
But there has never been such a trial, and that has made this subject a minefield for scientists and consumers alike.
Dr. Daniel W. Jones, a professor of medicine and physiology at the University of Mississippi School of Medicine and former president of the American Heart Association, was alarmed by the bitter arguments between researchers who disagree about salt. So he invited senior medical scientists on both sides of the debate to meet in Jackson, Mississippi, to figure out how to settle their differences.
“I wanted a balance between different points of view,” said Jones, who believes low-salt diets are healthier. “And I wanted people who had avoided the temptation of disparaging the motives of those who disagreed with them.”
Tellingly, those criteria “got me down to a small list of people to invite,” Jones said.
The six he invited agreed to sit down to hash out their differences. (He later invited two other researchers — Dr. Eric Peterson, a clinical trials expert at Duke University, and Dr. Robert Califf, also at Duke and a former head of the Food and Drug Administration — to weigh in on the final paper.)
Jones and Dr. David McCarron, a nutrition researcher at the University of California, Davis, who worries that low-sodium diets are dangerous to health, led the discussion. They began by putting the Institute of Medicine report before the group and highlighting the recommendation that there be a randomized clinical trial in a population whose diet can be controlled. They asked, “What are we going to do about it?”
“Is it not time for somebody to try to do this?” Jones said, recalling the conversation. “And if the answer is yes, what is the ideal population?”
For two days, the group debated and mulled over various options. Conduct the study among military personnel? Too young. Nursing homes? Too many residents are already prescribed low-sodium diets. The best option seemed to be people who were incarcerated.
So suppose you do the study in prisons, Jones said. Is the research supposed to benefit the prisoners or just the population in general? If the prisoners would not benefit, the study would be unethical.
People who are not incarcerated can choose how much sodium they consume, but prisoners cannot — they eat whatever the facility provides. If there is uncertainty about the ideal amount of sodium, the experts concluded, prisoners would benefit from a study that settled the matter.
The group consulted with Marc Morjé Howard, a professor of government and law at Georgetown University. He also teaches at a nearby maximum security prison.
“It’s a little bit of an ethical minefield,” Howard said in a telephone interview. “My concern would be that it not in any way be detrimental to prisoners’ health and it would be voluntary.”
But, Howard said, “I do think it is possible if it is done very, very carefully with the full cooperation of prison authorities.” He added that many incarcerated people have outgrown their criminal pasts and have a desire to help society. “They want to repent,” he said.
Macklin, in a telephone interview, also said many prisoners would be happy to jump in. She has taught in a maximum security facility and has studied the ethics of doing research in prisons. “They would say they want to give back to society,” Macklin said.
Prison administrators have told Jones they would be willing to consider a proposal for a randomized trial of salt. He will also be speaking to the American Civil Liberties Union, which runs a project on inmate rights, to explain the study and why it addresses important questions for prisoners.
The plan is to start with a pilot project involving prisoners aged 55 and over. That would be followed by a large trial lasting about five years and involving 10,000 to 20,000 prisoners in that age group. The researchers plan to request funding from the National Institutes of Health.
Jones said the trial at this point is just a proposal.
“There are a bunch of steps between here and there,” he said. “But we are a group of serious people, senior people who disagree strongly. We came together to find a solution.”