The worst damage may actually occur after treatment (Image: Robert Daly/Getty)

A common dietary supplement can massively reduce damage to the heart after a heart attack. The effect was seen in mice but if the same is true for humans, it has the potential to transform treatments for the developed world’s biggest killer.

Heart attacks generally occur because of a blockage in the arteries that prevents blood from getting to the heart. This can sometimes be fatal, but the worst damage may actually occur after treatment. When the blockage is removed, the sudden rush of oxygen-rich blood overwhelms cardiac cells and damages the tissue. This can cause death if enough cells are damaged and the heart stops beating.

Now it seems that a dose of iodide, a chemical with a long history of safe use in people, might prevent the worst of the damage.


“Iodide shows extraordinary benefit to the heart, I really think this has the potential to transform heart medicine,” says Mark Roth at the Fred Hutchinson Cancer Research Center in Seattle, Washington.

Metabolic overdose

When the heart is deprived of oxygen during an attack, the rate of oxygen consumption in the heart cells plummets. The cells slow down their metabolic activity by reducing the chemical reactions going on inside them, to make the most of the little oxygen available.

For reasons not yet completely understood, when blood flow is restored, metabolic activity and associated oxygen consumption in the cells leaps up to several times higher than it was before the attack. This results in the production of abnormal molecules, or metabolites, that aren’t recognised by the immune system. The immune system attacks these cells, causing what’s known as a reperfusion injury.

It is such an important problem that recently the US National Institutes of Health stated that a primary goal of heart medicine should be to prevent the heart from “metabolising itself to death”.

“We’re trying to hold back the horses,” says Roth, referring to his team’s attempt to prevent the sudden increase in metabolic reactions after treatment.

To do so, the team replicated a heart attack in mice by tying a thread around a main artery. They then either gave the rodents an injection of iodide or a saline placebo 5 minutes before removing the string – the equivalent of doctors using a small balloon to widen blocked arteries in people. Dissection of the mouse hearts showed that rodents that received iodide had 75 per cent less dead tissue than those that were given the saline.

Roth thinks the iodide might decrease the production or secretion of hormones by the thyroid, among other things. These hormones normally stimulate metabolic reactions, so depressing them may reduce cardiac metabolism.

Hearty benefits

Malcolm Bell at the Mayo Clinic College of Medicine in Rochester, Minnesota, warns that reperfusion has historically been a difficult nut to crack. “The whole reperfusion injury field is filled with failed therapies despite promising animal work,” he says.

Graham Nichol at the University of Washington in Seattle agrees that most therapies that help limit reperfusion injuries in animals have not been beneficial in humans, bar one or two exceptions. However, he says that he is very impressed by the size of the benefits in Roth’s study. “If it does work in humans, I think that will be because it works via multiple pathways, as opposed to previous failed therapies, which work on very specific pathways,” he says.

He says that a 75 per cent reduction in tissue damage would result in better heart function, so that people who survive heart attacks would be less likely to have heart problems in the future, and much less likely to die of heart failure. “I can’t give you a magic number of lives saved,” he says, “but it’s significant”.

Roth remains positive about iodide’s potential. He says it has been intensively studied for hundreds of years and is considered very safe for human consumption. Adults consume iodide every day, mainly by eating cereals and fish, and he points out that you can ingest 10,000 times the recommended daily allowance without experiencing any toxic effects.

“The safety and efficacy of iodine is hard to overstate,” he says. That means clinical trials could be approved relatively quickly – perhaps in the next year or two.

In the meantime, it is not known whether taking an iodide pill every day would help stave off heart attacks, but Roth says it’s unlikely, since the body would probably adapt to continuously high levels of the chemical. “Maybe eating a couple of pills before a cardiac bypass surgery might help you out,” he says, “it’s all worth us investigating”.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0112458