The production of new cells in flatworms can be hastened or slowed by weak magnetic fields, depending on their strength, a new study has found. Sadly, the work will probably be adopted by the charlatans who already claim to cure diseases with magnets, but it could eventually lead to genuine therapies, speeding the healing of wounds and slowing the growth of cancers.

Dr Wendy Beane of Western Michigan University led a team that exposed flatworms to magnetic fields not much stronger than those experienced naturally. The Earth's magnetic field, while strong enough to protect the planet from radiation, is a very subtle thing – try using a compass around anything carrying electricity or even slightly magnetic if you don't believe me.

“In many circles, it is assumed that the quantum of energy associated with these weak magnetic fields is too insubstantial to be biologically important,” Beane wrote in Science Advances. However, stronger magnetic fields are known to change the rates of chemical reactions, so it's possible to imagine even weak fields can have an effect. Previous studies done in cell cultures have produced contradictory results.

Beane chose planarian flatworms for their remarkable regeneration powers, as even their central nervous system can be restored thanks to a quarter of their bodies being adult stem cells.

When Beane exposed her worms to 200 microTesla magnetic fields, they produced the mass of cells, known as blastemas (which eventually become regenerated organs) more slowly than worms in natural strength fields. On the other hand, 500 μT fields induced faster blastema production. For comparison, the Earth's field is 25-65 μT.

Beane and co-authors think the fields are having an effect by altering the numbers of reactive oxygen species, a form of free radical molecules that can trigger cell death but also contribute to muscle repair and promote tissue growth in fish. In turn, Beane found the reactive oxygen species affect concentrations of heat shock protein 70, which promotes cell survival.

The potential benefits of a gentle way to encourage cell growth for healing wounds are obvious. However, since cancers are cells that proliferate when they shouldn't, magnetic fields that slow this behavior could buy time for other therapies to work. Although they have yet to demonstrate it in living animals, Beane's team have shown certain magnetic fields can reduce the growth of cancer cell cultures without interfering with non-cancerous cells.

Nevertheless, calibrating fields so they have the desired effect (not the reverse) is likely to prove a challenging process in creatures more complex than flatworms. Steer clear of anyone claiming their magic magnets can do the trick.