What are the side effects of digestive enzymes?

Don't know of any. Digestive enzymes are vital in the digestion (breaking down) of the large food molecules we eat so that they can be small enough to pass through the GI lining into our blood stream. There are enzymes to break down sugars, proteins and fats primarily. When taken as instructed, there should not be any side-effects to mention. Make sure the ones you are takng do not have allergens such as gluten.