Look, we have energy flowing through our body and flowing around us. and it's actually proven by science and it can be measured by meters. When you suffer from trauma, for example, an accident, that part of your body creates a block in that energy flow.
When the block is there, vitamins and essential nutrients are blocked as well. So, if this area doesn't get the necessary nutrients, it wont heal. Simple as that.
As a Reiki practitioner, you can "unlock" those blocks. You don't make nutrients flow to that location. You just destroy the block.
According to genetic researchers, your body has a wired-in "code" which automatically send nutrients there so that it can mend itself.
And the same goes for colds, wounds, arthritis and bunch of other diseases. The only reason they are there is because there is a block.
With Reiki, you learn how to exploit the life-force-energy that is all around us and direct it to the area and 'burn' away the blockage.