Magnetic Attraction

by Robert L. Park

Professor of Physics, University of Maryland
Director, APS Public Information Office, Washington, DC.

Paul doesn't let anything get in the way of golf. At 79, he plays almost every day, and he doesn't hold back a thing on his swing. So when Paul got a pain in his shoulder he took the advice of other golfers and bought a magnet therapy kit for $49.95. The current popularity of magnet therapy, like copper bracelets 20 years ago, seems to have started on the golf course. At first, golf pro shops were about the only place you could buy them. Now you can find therapy magnets in department stores, pharmacies and even my local Safeway.

Paul's handicap dropped from 20 to 17, and the pain in his shoulder went away. He's sure the magnets had something to do with it. His wife thinks so too. Since she began putting magnets in her shoes, she says she doesn't get as tired. Paul says he would recommend magnets for anyone.

But Paul admits he hasn't always followed his own advice. When he got a sore knee he didn't try magnets, he went straight to his doctor. A lot of friends his age have been diagnosed with osteoarthritis. That's really serious; not only will it mess up your golf game, it's not reversible. Fortunately, x rays showed no sign of osteoarthritis and the pain seemed to go away without any treatment.

Paul's knee got better by itself -- and I'd bet his sore shoulder would have too. Most of the things that afflict us get better by themselves. Our bodies have a very sophisticated repair kit for dealing with injury or disease: bones knit, blood clots, antibodies seek out infectious organisms, etc. That can make it pretty hard to tell whether the remedies we take actually help. Whatever we happen to be taking when we get better usually gets the credit.

Paul asked his doctor about magnets, but the doctor advised him that magnet therapy is not scientifically proven. 'That didn't surprise me,' Paul snorted, 'doctors always want to give you a pill. They think everything is internal. I don't know how magnets work, but they were using them in China thousands of years ago.' That's true, but the Chinese were also using powdered rhinoceros horn to restore virility. Unfortunately, they still do, with the result that the world is running out of rhinos. Rhinocerous horn and magnets are traditional treatments.

By contrast, the great medical advances today emerge from a detailed scientific understanding of how the body works. One new wonder drug, Viagra, may yet save the rhino from extinction. The road to modern medicine is littered with the bones of traditional treatments that millions of people once swore by - and are now known to be worthless or even harmful. Treatments such as purges and leeches were finally abandoned only when they were objectively compared to simply allowing the illness to take its course. Magnet therapy, it seems, has been abandoned several times over the centuries - only to be revived.

Animal Magnetism

In the early 16th century, the power of lodestone (magnetite) to attract iron filings without touching them suggested great power. Paracelsus, the famous Swiss alchemist and physician began using powdered lodestone in salves to promote healing. William Gilbert, however, physician to Queen Elizabeth I, and father of the scientific study of magnetism, pointed out that the process of grinding the lodestone into powder destroyed the magnetism. Nevertheless, a century later, magnetic cures were introduced into England by Robert Fludd as a remedy for all disease. The patient was placed in the 'boreal position' with the head north and the feet south during the treatment.

By far the most famous of the magnetizers was Franz Mesmer (1734-1815), who carried the technique from Vienna to Paris in 1778 and soon became the rage of Parisian society. Dressed in colorful robes, he would seat patients in a circle around a vat of 'magnetized water.' While Mesmer waved magnetic wands over them, the patients held iron rods protruding from the vat. He would later discover that the cure was just as effective if he left the magnets out and merely waved his hand. He called this 'animal magnetism.'

Benjamin Franklin, in Paris on a diplomatic assignment, suspected that Mesmer's patients did indeed benefit from the strange ritual because it kept them away from the bloodletting and purges of other Paris physicians. Those physicians bitterly resented Mesmer, an outsider who was attracting their most affluent patients. At the urging of the medical establishment, King Louis XVI appointed a royal commission to investigate his claims. This remarkable group included Franklin, then the worlds greatest authority on electricity; Antoine Lavoisier, the founder of modern chemistry; and Joseph Guillotine, the physician whose famous invention would one day be used to sever the head of his friend Lavoisier.

The commissioners designed a series of ingenious tests in which some subjects were deceived into thinking they were receiving Mesmer's treatment when they were not, and others received the treatment but were led to believe they had not. The results established beyond any doubt that the effects were due solely to the power of suggestion. Their report, never surpassed for clarity or reason, destroyed Mesmer's reputation in France, and he returned to Vienna.

Nevertheless, magnetic therapy eventually crossed the Atlantic. Its most famous practitioner in the United States was Daniel Palmer, who in 1890 opened Palmer's School of Magnetic Cure in Davenport, Iowa. Like Mesmer, Palmer soon discovered that his patients recovered just as quickly if he omitted the magnets and merely 'laid on hands.' Thus was founded 'chiropractic therapy,' and the school became Palmer's College of Chiropractic.

New Age Magnetizers

In recent years, an enormous amount of research has been done on the effect of magnetic fields on the human body, driven not by magnetic therapy, but by safety considerations associated with the phenomenal growth in the use of magnetic resonance imaging (MRI) for medical diagnoses and research. MRI subjects the whole body to a magnetic field about a hundred times stronger than the localized field of even the most powerful therapy magnet. Happily, no ill-effects been found from exposure to MRI fields. Indeed, there are almost no effects at all -- just a few reports of faint sensory responses, such as a slight metallic taste and visual sensations of flashing lights if patients move their eyes too rapidly. The fact is that the stuff we're made of just isn't very magnetic.

That's why scientists were surprised two years ago when Dr. Carlos Vallbona at the Baylor College of Medicine in Houston reported results of a double-blind trial of magnets in the treatment of 50 patients suffering post-polio pain. Some of the patients were treated with commercial therapy magnets, others were treated with sham magnets. Seventy-six percent of those treated with real magnets reported a decrease in pain, while only 19 percent receiving the placebo felt an improvement.

But there have been no confirming studies by other researchers, and Leonard Finegold, a biophysicist at Drexel University, found problems in the protocol used in the Baylor trial. Physicists might be more inclined to take the Baylor results seriously if there were some plausible explanation of how the magnets work. The most frequent claim, which Vallbona supports, is that magnets promote the flow of blood to the treated area.

It's easy to check. An excess of blood shows up as a flushing or reddening of the skin. That's why the skin turns red when you apply heat; blood is being diverted to the heated area to serve as a coolant. But you will discover that placing a magnet of any strength against your skin produces no reddening at all. There is no indication that Vallbona tried this.

The argument is that blood, because it contains iron, should be attracted by the magnets. The iron in hemoglobin, however, is not ferromagnetic. The hemoglobin molecule itself is very weakly paramagnetic, but the fluid that carries the red cells, consisting mostly of water, is diamagnetic - it is weakly repelled. Indeed, small animals have even been levitated in powerful magnetic fields.

It has also been suggested that a magnetic field aligns water molecules in the blood, somehow improving circulation. But in fact, no alignment of water molecules is observed even at the field strength of MRI magnets. At the temperature of blood, water molecules are jostling each other so violently that their orientation is randomized. To align them, a magnetic field would have to be strong enough to overcome the thermal energy. Dr. John Schenck, at General Electric's R&D Laboratory, the leading authority on the effect of MRI fields on the body, calculates that fields thousands of times stronger than any that have ever been generated on Earth would be needed to align even one percent of the water molecules.

So how strong are the fields of therapy magnets? In a kit like the one Paul bought, the gold-plated neodymium alloy magnets are rated at 800 gauss, measured at the surface of the magnet. That's not much compared to the 30,000-40,000 gauss electromagnets used in modern MRI, but it's a lot for a small permanent magnet.

The current revival of magnetic therapy is, in fact, due almost entirely to remarkable advances in materials science. New permanent magnet materials based on ferrites and rare-earth alloys are one of the un-sung triumphs of modern materials science. These new magnets are essential to high-tech products ranging from miniature walk-man headphones to laptop computers. They can be fabricated into all sorts of shapes, even thin and flexible, allowing them to be inserted into shoes or sewn into mattresses. No one was going to put lodestones in their shoes, or be seen on the golf course wearing old fashioned horseshoe magnets.

The makers of therapy magnets warn against using them 'around credit cards or during pregnancy.' The instructions with Paul's kit, however, showed a magnet being worn on the wrist. Now your wrist normally passes within an inch or so of your hip pocket when you walk. That's where most men keep their credit cards - and 800 gauss is certainly enough to wipe out the magnetically-coded information on the cards.

Since the people who make these magnets are often paid with credit cards, they presumably have an interest in seeing to it that your cards stay in good working order. Could it be that they make therapy magnets the way refrigerator magnets are made? Since refrigerator magnets are only meant to hold phone messages and Dilbert cartoons, they are designed to have a very short range field. This is done by making them in the form of narrow strips of alternating north and south poles. You can test this. Take two identical refrigerator magnets (the thin flexible kind, not the molded ceramic ones that look like a piece of fruit). Slide one across the other. You can feel them click into place each time the poles line up. Right at its surface, such a magnet may be quite strong, but a very short distance away, depending on the width of the strips, the north and south poles will effectively cancel.

The magnets in Paul's kit were disks about the size of a quarter. They were in little Velcro pouches that can be attached to blue velvet bands that are wrapped around the injured area. They must look dashing in the fitness center. I removed two of the magnets from their pouches and slid one across the other. I could feel them clicking into place - they were just like refrigerator magnets.

To get an idea of how quickly the field falls off, I stuck one of the magnets on a file cabinet. I then held sheets of paper between the magnet and the cabinet until the magnet could no longer support itself. Ten sheets! That's just one millimeter. The field of these magnets would hardly reach through the skin, much less into muscles and joints. Indeed, there was essentially no field extending through the velvet bands. Not only do these magnets have no power to heal, their fields don't even reach the injury. So much for the Baylor study which used commercial alternating-pole magnets. You might characterize them as 'homeopathic' magnets.

As medical scams go, magnet therapy may not seem like a big deal. Magnets generally cost less than a visit to the doctor and they certainly do no harm. But magnet therapy can be dangerous if it leads people to forego needed medical treatment. Worse, it tends to reinforce a sort of upside-down view of how the world works, leaving people vulnerable to predatory quacks if they become seriously ill. It's like trying to find your way around San Francisco with a map of New York. That could be dangerous for someone who is really sick - or really lost.

Robert L. Park
Professor of Physics, University of Maryland
Director, APS Public Information Office, Washington, DC.
(author of Voodoo Science: the Road from Foolishness to Fraud)

Note: Part of this essay was originally published in the 'Physics & Society' Newsletter. sincerely thanks the editors of this publication and the author, Prof. Robert L. Park, for giving us the permission to publish this essay on