Magnet Therapy - how does it work?

There is a sort of rationale to thinking that magnets might have some curative properties. After all, blood contains haemoglobin which is a molecule in blood cells that contains iron, and we know that iron is magnetic. We also see magnets used in hospitals for use in scanning people. So it's a small step to thinking that magnets might have a more general healing application.

We can now buy a wide range of magnets, in all shapes and sizes, for wearing around the wrist or neck, or even for fitting in our shoes. Marketers of these devices are keen on generating sales and so typically there is very little in the way of explanation of how they might work. As a result, many people buy one to see what happens.

There is a large number of anecdotal accounts from people claiming they have spent their money well. Although that is only to be expected, we should not discount what they say simply because they paid for magnets. We should also expect it to be trialled and tested. To evaluate the claims, we need trials which are controlled, double-blind and randomised so that the bias is systematically eliminated. But first we need to think about what effects are claimed for magnets.

What's the theory behind magnet therapy?

There are two main theories which make therapeutic claims for magnets. One of them stresses the connection between magnetism and electricity. It is a well-known physical phenomenon that moving electrical fields produce magnetic effects and vice versa. The fundamental physics relating electricity and magnetism was carried out during the nineteenth century so it is reasonable to expect magnets to have some electrical effect. It is claimed that the electrical effect, has an impact on the functioning of human tissue.

The second theory is typically some variation on the idea that magnetic forces pull the blood because blood contains iron. Sometimes it is claimed that the blood circulation is increased, with a consequent increase in oxygen, and ion exchange. These things in themselves are seen as curative. And at first sight, it seems plausible.

Problems with the theory

The devices sold in shops are what are called static magnets, because they produce a constant magnetic field. These magnets do not produce any electrical voltage in nearby tissue because that only happens when the magnets are vibrated. So magnets in the form of bracelets, earings, pendants, shoe inserts, and so on, cannot have any electrical effect on tissues. This connection between electricity and magnetism has been known as long ago as the 1800s when Michael Faraday carried out his experiments, but the manufacturers either don't realise, or don't want to publicise it.

If the static magnets can't have the electrical effect claimed of them, perhaps then they work on the principle of attracting blood and increasing circulation. But here again, we have a problem. If blood was magnetic, we could draw it in a particular direction. In fact, this would be rather dangerous if anything because if we left a magnet on our skin, the blood would tend to accumulate there and produce a bruise. The fact that this doesn't happen is easily explained - blood is not magnetic. Even though it contains iron, that iron is not in the same form as a for example an iron nail, but it is distributed chemically combined to a protein, globin to form haemoglobin.

So that pretty much rules out the two usual explanation offered but there might be another one, based on the known physical effects of moving magnets. If we managed to make the magnetic field pulsate, then this could induce an electric current, and we might be back in business. Indeed this idea was so appealing that medical researchers have investigated it thoroughly. Healing rates for fractures and other tissue damage have been compared with and without the use of pulsating magnets but the well-designed studies involving control groups showed no evidence of magnets having any effect.

It has also been suggested that because magnetic fields also affect ions in the blood, that this effect can induce heat. It is called the Hall effect and it is a genuine scientifically established but infinitesimally small effect. And that's the problem. Even with a powerful pulsating electromagnetic field, the actual effect on the tissue is barely detectable, and has no physiological effect.

When hospitals use scanning equipment using MRI (magnetic resonance imaging), they are using very powerful electromagnetic fields to very slightly affect hydrogen atoms inside the water in the body, a tiny change which enable the detection of the difference between hard and soft tissue. Just to be able to produce an image, a massive magnet is required and all it produces in the tissue is a tiny transient effect with no physiological consequence. That should make us understand a little about the strength of magnetic fields required to affect human tissue.

Even if such fields were directly alongside the tissue, the effect could not be detected. But in practice, the magnetic field has to penetrate tissue, which reduces its strength. The fall-off in strength of the field is actually an inverse square law: double the distance, half the effect. So if you can detect a small field at 1mm, by the time you get to 16mm, it is less than 1/250 of the effect. At 32mm it's less than 1/1000th. So any device trying to use the effect for therapeutic purposes needs to be impossibly close to the tissue to have any effect at all.

The bottom line?

Although it seems appealing as a theory, both because it talks about scientific phenomena and to the lay person seems plausible, unfortunately it doesn't work. The effects claimed can't work for sound physical reasons. Electricity and magnetism just don't work the way it is claimed by people who sell these devices. Even if we stretch credibility a little and talk about very strong pulsating magnets, we can still detect no physiological effect.

There are good obvious objections to the theories as well. If we held a magnet and they attracted blood, we'd end up with bruises just by carrying one. We don't.

We'd all like to be able to take advantage of some simple yet effective method of treating illnesses but unfortunately, we can't dictate how physics and the human body works. Therapeutic magnets are based on wishful thinking and less than honest marketing. It is shame that something that sounds plausible and potentially very useful, fails to deliver because the world just doesn't work that way. But understanding a little about the physics could save us a lot of money.