The logistics of a large-scale, randomized nutrition study are challenging. Ensuring people rigidly follow their meal plans and participate in the requisite check-ups is nearly impossible in a real-world setting.

To help define ideal dietary sodium levels, researchers have proposed turning to a truly captive population: prisoners. In this tightly controlled environment, it would be feasible to collect data that could finally help resolve the debate about whether low-sodium diets are preventive against hard outcomes like stroke and death.

According to the New York Times, there has never been a randomized clinical trial evaluating sodium’s impact on those hard endpoints. Some scientists have pointed to other studies that suggest low-sodium diets don’t reduce those events at all, saying perhaps human craving of salt indicates a need for it to properly function.

But studying inmates comes with its own ethical hurdles, Marc Morjé Howard, PhD, JD, told the Times.

“My concern would be that it not in any way be detrimental to prisoners’ health and it would be voluntary,” said Howard, a professor of government and law at Georgetown University who teaches at a maximum security prison. “I do think it is possible if it is done very, very carefully with the full cooperation of prison authorities.”