This is what I pulled out of the internet on all enteral nutrition formulae, not Ensure or Ultracal in particular:
"Side Effects of This Enteral Nutrition Formula
Some problems may result from improper use of an enteral formula or use of the incorrect formula in your condition. Check with your doctor if any of the following problems occur:
Confusion, convulsions (seizures), decrease in urine volume, dryness of mouth, frequent urination, increased thirst, irregular heartbeat, mood or mental changes, muscle cramps or pain, numbness or tingling in hands, feet, or lips, respiratory distress, shortness of breath or difficulty breathing, unexplained nervousness, unusual tiredness or weakness, weakness or heaviness of legs, weak pulse"
On Ultracal I had the confusion, frequent urination, dry mouth, mood changes, constipation, and numbness. Of course, it could have been from the radiation, but I did start feeling a lot better when I got off the Ultracal and started surviving on yogurt smoothies, milk shakes, spam, etc.