A belief in the healing power of magnets has been around since ancient Greece, leading to a $5 billion a year worldwide industry that supplies millions of believers with magnets for everything from arthritis to cancer to depression.
That's despite the fact that numerous scientific studies have been either inconclusive or unable to find evidence to support the claims of their healing power.
New research at the University of Virginia shows that there is at least some truth to the oft-cited claim that magnets can increase the flow of blood, thus providing more oxygen and nutrients to injured tissue. Researchers have shown that a mild magnetic field can cause the smallest blood vessels in the body to dilate or constrict, thus increasing the blood flow and suppressing inflammation, a critical factor in the healing process.
So far, the findings are based on experiments with rats, but the researchers hope to begin human clinical trials in the near future, although that could prove to be a major challenge.
What sets this work apart from most research into the so-called healing effects of magnets is the fact that the researchers were able to quantify their results by measuring the changes in the blood vessels to determine the impact on inflammation.
"It's the first direct measurements that show the reduction in swelling," said Thomas Skalak, chairman of biomedical engineering at the university, who reported on his work in the American Journal of Physiology. Skalak and a former student, Cassandra Morris, have been trying to nail down the effects of magnetism for several years now.
Their findings do not lend credence to the wild claims of many manufacturers of magnetic cure-alls. Instead, their work was very precisely focused on the claim that magnets can increase the flow of blood.
"We wanted to find out if that was true," Skalak said in an interview.
The researchers used anesthetized rats for their work. The rats' paws were treated with inflammatory agents to simulate tissue damage, and a small magnet, about 10 times more powerful than a basic refrigerator magnet, was attached to their paws. The swelling was reduced by about 50 percent, apparently because the magnetic field changed the diameter of the blood vessels. The magnet only had to remain in place for 15 to 30 minutes. If the researchers waited until after the paw was fully inflamed, the magnet had no effect.
If magnets work that well in human trials, the impact could be dramatic, because in many cases reducing inflammation is essential to a speedy recovery.
"Let's say it takes you four or five days to recover from a given injury and get back to work, or back on the athletic field," Skalak said. "If by preventing the swelling you recover after two days, you've cut the healing time by a factor of two. That's tremendous savings worldwide in worker productivity and the quality of life."
Of course, similar results can also be achieved by applying an ice pack and compression, but that's not always convenient. A magnet, of just the right power, could be carried in a school nurse's packet, or in an athletic trainer's bag, and always be available within seconds of an injury. But at this point no one knows just the right dosage, or in this case the necessary magnetic strength, to match up with which injury.
One size won't fit all. Skalak said it would take a much stronger magnet, for example, to treat a thigh muscle than a sprain in the small finger. And, as he pointed out often during the interview, no one knows yet if it will work at all in humans.
But Skalak sounds optimistic, based on many years of experience in a relatively narrow field. He is an expert on the smallest blood vessels in the body, ranging from five to 200 microns in diameter, or about one fifth of a millimeter.
"These are very small blood vessels, and they are in all the tissues in your body," he said. "We like to think that's where the action is. That's where oxygen gets delivered, and it's where waste products get removed from your tissues.
"These small arterials can open and close because they have a layer of smooth muscle wrapped around them," he added. "They can increase their diameter, thus delivering more flow to a given tissue, and they can decrease the diameter, just like opening and closing a garden hose changes the flow of water."
When a magnetic field was applied to the paws of the lab rats, the vessels that had been dilated constricted, and the constricted vessels dilated, suggesting that the magnetic field "induced vessel relaxation in tissues with constrained blood supply, ultimately increasing blood flow."
The mechanism is not fully understood, he added, but he suspects the magnetic field alters the flow of positively charged calcium ions that interact with the muscles around the small blood vessels, causing them to dilate or constrict.
Skalak worries that his study will be taken out of context and used to boost sales of magnetic gizmos that are not supported by medical evidence. He's probably right.
Magnets are attractive to many, and their use has been widespread for several centuries. Early believers thought magnets might pull diseases and pain from the body, a belief that persists to this day, despite the lack of evidence.
However, magnets have proved to be a valuable tool in medicine for a wide variety of uses. A number of researchers are developing techniques to use small magnets to draw chemotherapy-carrying magnetic particles into tumors and hold them there, thus killing cancerous cells while sparing nearby healthy cells.
And magnets are at the heart of one of modern medicine's most useful techniques, magnetic resonance imaging. This device gives doctors precise images of the entire human body in amazing detail.
But it's no simple contraption, and it's not your ordinary magnet. The strength of a magnetic field is measured in gauss. Earth's magnetic field, measured at the equator, is .2 gauss. An MRI is up to 30,000 gauss.
So magnets, like human injuries, come in many complex forms. Skalak hopes his work will lead to magnets that can be used on a very personal level, proving the ancients got it at least partly right.