This is meant to be simple, from a diabetic, not a doctor.
Diabetics do not make (type 1), or do make enough (type 2) insulin. Insulin is a hormone that takes the sugar, starches, and other food, and converts it to energy. Without insulin, a type one diabetic would starve, even if eating. The sugar is trapped in the blood, and unusable.
Because it takes time for the insulin we take as diabetics to work, sugar stays in the blood longer. Sugar feeds yeast.
In my opinion as a diabetic, eliminating as much sugar, and starch as possible, and adding Probiotics (friendly bacteria) are the best defense.