For many, it's not necessary to know how magnets work - it's enough that they find some relief while using them. Nevertheless, at a time when scientific explanations lend commercial credibility to a product, many theories have been put forward. Some believe that magnets react with iron in the blood to increase blood flow. Others believe that magnets desensitise sensory neurons, reducing pain in the treated area. Also put forward are an increased oxygen content and increased alkalinity of bodily fluids, magnetic forces on moving ions and decreased deposition on blood-vessel walls.
The broadest explanation was offered by Dr Kyochi Nakagawa in 1976, published in the Japan Medical Journal. He claimed that many chronic health conditions arise because of 'magnetic field deficiency syndrome'. Indeed, the earth's magnetic field has decreased by about 6 per cent since 1830, and possibly by as much as 30 per cent over the last millennium. Dr Nakagawa argues that magnetic therapy replaces some of this lost magnetic field.
While our understanding of how magnets work may not have come very far, the technology for producing magnetic material has advanced in leaps and bounds.
Unlike earlier magnetic materials such as steel, which is easily demagnetised, new magnets made from materials such as ferrite (ceramic) or rare-earth materials such as neodymium-iron-boron are much more powerful and harder to demagnetise (early magnets had to be long and thin to avoid being demagnetised by the internal fields produced by their end poles). This allows modern magnets to be used in a variety of thin, flexible products that can be moulded to various areas of the body.
The robustness of modern magnets also means that manufacturers can produce multipolar (or bipolar) devices, which have alternative north and south poles, rather than unipolar devices in which only the north or south pole of the magnet faces the body. Unipolar devices tend to have a stronger surface field while multipolar magnets are thought to be more natural and healthful, though this has not been firmly established.
Pulsed or fixed?
The plethora of research into magnetic therapy is generally divided into two distinct areas: pulsed bioelectric magnetic therapy (PEMF, which uses electromagnetic fields, or EMFs); and fixed magnetic therapy (which uses static magnetic fields). Around 90 per cent of the literature focuses on PEMFs, shown to be effective in healing bone fractures and, to a lesser degree, soft-tissue injures such as sprains and strains. Indeed, the US Food and Drug Administration approves the use of pulsed EMFs for treating non-union bone fractures (those that don 't heal on their own). Other uses for EM devices include wound-healing, osteoarthritis and rheumatoid arthritis (Rheum Dis Clin North Am, 2000; 26: 51-62) as well as heart attack, stroke and diabetes (J Cell Biochem, 1993; 51: 387-93).
The benefits of PEMFs are believed to arise from biological effects of these induced electric fields. Although this is not the case with fixed magnets, many health claims for such magnets are extrapolated from PEMF research.
Success with pain
While proponents of fixed magnetic therapy claim benefits such as increased energy and strength, few studies have focused on these hard-to-quantify effects. Fixed magnets are usually studied for pain relief. The earliest studies found no benefit to neck and shoulder pain from wearing magnetic necklaces (Arch Phys Med Rehab, 1982; 63: 462-6).
This finding was echoed in a more recent study of the effect of bipolar magnets on chronic low back pain. Real (300-G) and sham magnets were applied on alternate weeks for six hours a day, three days a week for one week (with a one-week break between treatments). No immediate or cumulative pain-relief was observed (JAMA, 2000; 283: 1322-5).
Other results have been more positive. In one double-blind randomised study - the 'gold standard' of medical research - of 300 to 500-G magnets on chronic postpolio pain, participants in both groups reported significant pain relief after a single 45-minute treatment, although the real magnets appeared to produce a greater degree of relief (Arch Phys Med Rehab, 1997; 78: 1200-3).
Case reports suggest that magnets (700-800 G) applied to specific acupuncture points on the legs may help relieve migraine (Acupunct Med, 1995; 13: 51-3). Fixed magnets may also help postoperative pain (Plast Reconstr Surg, 1999; 104: 2261- 6), but studies into whether magnets can increase circulation (Bioelectromagnetics, 2001; 22: 494-502) or muscle strength are disappointing.
While there is evidence that magnetic insoles are no better than sham insoles for heel pain (J Am Podiatr Med Assoc, 1997; 87: 11-6), they may benefit those with chronic neuropathological symptoms. In one randomised placebo-controlled trial, patients enduring burning pain, numbness and tingling in the extremities used a 475-G magnetic foot insole on one foot and a sham insole on the other. After 30 days, the insoles were switched, so the other foot was getting the benefit of the magnet. After another month, the participants received two new 475-G insoles.
The insoles were particularly effective for those whose neuropathy was a consequence of diabetes - 90 per cent vs 33 per cent of those with neuropathy due to other problems, such as alcoholism (Am J Pain Manag, 1999; 9: 8-17).
While the accumulated evidence suggests that it may be worth adopting an open mind towards the effects of permanent magnets, the electrochemical processes of the human body are extremely complex and not entirely understood. Some effects may be positive; others may be negative, but this can only be determined by longer-term research - which is not being done.
Like any other therapy, positive results may depend on accurate, individual diagnosis and appropriate application rather than a magic-bullet approach.
Magnetic insoles are not as popular as they once were, but are still very much in evidence in catalogues and on the Net. While some manufacturers declined our offer to participate in our road test, we did manage to obtain products from four leading manufacturers; these were passed on to 10 volunteers in the PROOF! Panel. Each Panel member has a chronic fatigue syndrome. We reasoned that, if magnetic insoles really do bolster physical energy, then these testers are more likely to notice such increases. Indeed, we are indebted to our Panel for testing these products, and providing such comprehensive and cogent comments on their use.
The evaluations are based on several points, including how much information there was on the packaging, whether the insoles were easy to fit into regular shoes, whether they were comfortable, and whether there were any adverse and/or positive effects such as increased energy. Each tester wore the insoles for five days, followed by a two-day break, before moving on to the next product. This may seem a very short time, but proponents of magnetic insoles strongly believe that any benefit should be felt immediately - which, in some cases, they were.
This could be interpreted both positively and negatively. As several of our testers noted, chronic fatigue leaves you with unpredictable energy levels. Nevertheless, some reported increased energy that was virtually immediate (other improvements included a decreased tendency toward restless legs and, in one diabetic woman, less numbness of the toes). However, for every action, there is a reaction. As one tester put it, ''By the end of the week, I could only sit immobile for two days.'' Another said, ''I had more mental energy than was good for my physical capacity.''
Two of our Panel felt that the higher gauss rating of the HoMedics and Norstar insoles may have been too much for them. But apart from a kind of rebound exhaustion, negative effects from the insoles were infrequent, and included symptoms like headache, sore feet and a feeling of having a raised blood pressure.
The information supplied with each product varied enormously. MagneCare's insoles came with no information and no instructions, which many found frustrating. AcuMedics ' MagSoles included a useful reflexology map of the foot and a clear list of precautions (not found with all the other products), but failed to tell users much about the insoles themselves (for instance, the gauss rating).
In contrast, Norstar's Powerstrides and HoMedics' Thera-Ps provided copious information, though several users pointed out that this bumpf often amounted to sales pitches rather than useful information. As one panellist commented, Norstar promised ''deeper relief - but from what?!'' Likewise, most consisted of largely unproven claims such as ''improves blood flow'', ''stronger circulation'' and ''heals your body naturally''.
Most of these products had to be trimmed to fit, and instructions on how to do this varied. The Thera-P insoles ' instructions were almost incomprehensible to our Panel (and to us). While most products supplied templates, it 's better to stand on the insole and have someone trace your foot. This method results in the best fit.
One problem unmentioned by all manufacturers was that the thickness of the insole can make your shoes feel too tight. While not a problem if you wear loose trainers all day long, it may make wearing more formal shoes impossible.
Distributor: Norstar Biomagnetics
Of all the products tested, this inspired the greatest confidence and had the most noticeable effects on our users. Of heavy, sturdy construction (so much so that trimming was a problem for some) and likely to last well - and good thing, too, since they 're the most expensive in our survey - each insole has a core-magnet rating of 2500 G and a surface rating of 150-200 G. Norstar claims that the magnetic field will penetrate up to three inches into the body. Included was a template for trimming the insoles and a FAQs booklet about magnetic therapy and other Norstar magnetic products. The suggestion that users drink three glasses of water a day to aid detox was unique and was viewed by most as positive. Two panellists continued using these insoles after the test, but two others complained that they produced foot pain.
Thera-P Magnetic Insoles
The most user-friendly of the insoles tested, HoMedics covers these with a soft reassuring blue fabric. They were perceived as easy to trim - as long as you completely ignored the unnecessarily complex instructions provided by the manufacturer.
The insoles feature a pattern of alternating north and south poles of 400-plus-G strength at the core (the surface gauss rating would be much less, and is not stated on either the packaging or in the advertising material). Included, however, was a useful foot reflexology chart and the promise that you could ''energise your body through your feet!''
This is a daunting pair of insoles at first glance, with raised metal studs protruding from the practical rubbery material. In the end, opinion was clearly divided as to the benefits of this type of insole.
''Wearing them without socks was like walking on a bed of nails,'' commented one tester. Even with socks, many still found them difficult to wear. Two of our panel complained that they developed blisters within a couple of days of use. Another stopped using them altogether after two days because of the discomfort.
While reasonably priced and helpful to some, they are evidently not for everyone.
First impressions are important, and none of our panel was impressed by the uninformative packaging and ''bumpy'', ''rubbery'' feel of these insoles. However, all is not lost. The bumps on these were less pronounced than on the AcuMedic insoles and some panellists found them to be more comfortable than expected, at least at first. But, as the day wore on, several found the bumpy surfaces uncomfortable.
The general consensus was that, although these were durable and provided some acupressure-type stimulation of the feet, they did not appear to produce any detectable change in energy levels.