Reducers turn the ionic silver (silver oxide dissolved in water) you create with the electrolysis cell into colloidal form. They're reducing sugars (glucose, maltodextrin,...) though there are some others like cinnamon tincture...
The reducing sugar rips the oxygen off the silver oxide which leaves nothing but pure nanoscopic silver particles - a.k.a colloidal silver.
The amount of reducing sugar you need amounts to maybe 1 calorie, if even that. Thats NOT going to raise your blood sugar.
To make a liter of 20PPM, you need about 1 drop of Karo to reduce it all.
Karo isn't a great stabilizer though so you can't use it over 20PPM. For higher PPMs, maltodextrin is the reducer of choice. If you're gel capping any reducer is fine because the gelatine becomes the stabilizer.
The amount of glucose you need to reduce a liter of 20PPM is microscopic.