Furthermore, the worms near the south pole of the horseshoe magnet were fatter and more active than the worms near the north pole of the horseshoe magnet. Another curious incident is that an Alzheimer's patient completely regained his sense a few hours after MRI scan. Dr. Carlos Vallbona conducted the study on fifty post-polio patients using magnets and visually identical sham magnet. He kept the study double blind by not telling which were active magnets and which were sham magnets to both the patients and the staff. If the double blind study was conducted successfully, then we cannot conclude the effect of magnet therapy as a placebo effect.
Blood contains electrically charged ions.
So the magnetic field exerts a force to electrically charged ions in flowing blood. The induced Voltage will in turn will produce heat. However both the force exerted by magnetic field to charged ions and induced Voltage is extremely small compared to the forces already exist in the flowing blood. So it is really unlikely to say that these effects have any biological significance. Following example will illustrate the weakness of the force and Voltage induced by static magnetic field.