image Long popular in Japan, magnet therapy has recently entered public awareness in the United States, stimulated by golfers and tennis players extolling the virtues of magnets in the treatment of sports-related injuries. Magnetic knee, shoulder, and ankle pads, as well as insoles and mattress pads, are widely available and are touted as providing myriad healing benefits.

However, despite this enthusiasm, there is not much in the way of reliable scientific evidence to support the use of magnets for these conditions.

Types of Magnet Therapy and Their Uses

The term "]]>magnet therapy]]>" refers to the use of static magnets placed directly on the body, generally over regions of pain. (A static magnet is an ordinary permanent magnet, as opposed to an electromagnetic coil.) Static magnets are either attached to the body by tape or encapsulated in specially designed products such as belts, wraps, or mattress pads.

Static magnets come in various strengths. The units for measuring magnet strength are gauss and tesla. One tesla equals 10,000 gauss. A refrigerator magnet, for example, is around 200 gauss. Therapeutic magnets measure anywhere from 200 to 10,000 gauss, but the most commonly used measure 400 to 800 gauss.

Therapeutic magnets come in two different types of polarity arrangements: unipolar magnets and alternating-pole devices. Magnets that have north on one side and south on the other are known, rather confusingly, as unipolar magnets. Bipolar or alternating-pole magnets are made from a sheet of magnetic material with north and south magnets arranged in an alternating pattern, so that both north and south face the skin. This type of magnet exerts a weaker magnetic field because the alternating magnets tend to oppose each other. There are many heated opinions—with no supporting evidence—on which one is better.

How Does Magnet Therapy Work?

A commonly held misconception is that magnets attract the iron in the blood, thus moving the blood and stimulating circulation. However, because iron in the blood is bound to hemoglobin, it is not free to respond to a magnetic field. Static magnets could affect charged particles in the blood, nerves, and cell membranes or subtly alter biochemical reactions; however, biophysicists are skeptical that commercially available static magnets are strong enough to significantly affect the body. (The moving magnetic fields of electromagnets exert a different kind of effect, and there is little doubt that they can affect nerve tissue and possibly other parts of the body as well.) One rigorously designed double-blind trial found that commercially available static magnets have no effect on blood flow. Another found hints that static magnets might affect muscle metabolism, but further research will be necessary to sort out this possibility.

What Is the Scientific Evidence for Magnet Therapy?

In double-blind, placebo-controlled trials, static magnets have shown promise for a number of conditions, but for no condition is the evidence conclusive.

For example, a six-month, double-blind, placebo-controlled trial of 119 people with ]]>fibromyalgia]]> compared two commercially available magnetic mattress pads against sham treatment and no treatment. Group 1 used a mattress pad designed to create a uniform magnetic field of negative polarity. Group 2 used a mattress pad that varied in polarity. In both groups, manufacturer’s instructions were followed. Groups 3 and 4 used sham treatments designed to match in appearance the magnets used in Groups 1 and 2. Group 5 received no treatment. On average, participants in all groups showed improvement over the 6 months of the study. Participants in the treatment groups, especially Group 1, showed a hint of greater improvement; however, the differences between real treatment and sham or no treatment generally failed to reach statistical significance. This outcome means that the benefits seen could have been due to chance.

Other small studies have evaluated magnet therapy for the treatment of ]]>peripheral neuropathy]]> , ]]>rheumatoid arthritis]]> , healing after liposuction, ]]>post polio syndrome]]> , knee or back pain, chronic pelvic pain, and ]]>carpal tunnel syndrome]]> , but the results could not reliably show benefit.

One study shows the general difficulties to be met in determining the benefits of treatments for pain conditions. This double-blind, placebo-controlled study of 30 people with carpal tunnel syndrome found that a single treatment with a static magnet produced dramatic and long-lasting benefits. However, identical dramatic benefits were seen in the placebo group. Thus, this study supports other trials that found placebo treatment quite effective for the treatment of pain, but provides no evidence for the effectiveness of magnets per se.

The Bottom Line

So, are magnets really so attractive when it comes to alleviating pain? Given the current evidence, it’s difficult to say. You may experience some benefit, but it is not clear whether the treatment will cause any improvement above and beyond what a placebo could do. Only further scientific study can answer this question.

Additionally, patients with a pacemaker or other implantable medical device such as a defibrillator, insulin pump, intrathecal pump, or a chemotherapy infusion pump should avoid using magnets as they may interfere with the function of these devices.