If you are trying to maintain optimal health or trying to recover from and illness (long or short-term), then there is one key things to consider; stay away from corn (unless it's organic) & soy and corn/soy by-products. By-products of corn and soy are known to come from GMO crops and cause digestion and other health issues.
Always check the label and see what is in the list of ingredients.
The following list are extensive and some of the by-products, if organic, my be okay to consume.
List of corn by-product: http://www.cornallergens.com/list/corn-allergen-list.php