I would be quite surprised if you had any ill effects unless you have a medical condition for which you require a special diet. I don't know what you usually eat but I eat mildly healthy meals usually (no excess sugar, carbs, sodium, fat or cholesterol) and based on the igedients list on my Mainstay rations I'd say they are about the healthiest thing I eat. Granted they are designed for survival and specifically short term survival, which is why they contain little fiber and almost no protein. I have never gone for more than a few days on Mainstay and water alone, but I think with a protein supplement like whey and a good source of fiber like spinach to keep the plumbing functioning well (a diet of mainstay and water makes for a lot fewer BMs than a normal diet), I could probably go a lot longer. Don't know that I'm gonna try it but if I did you fine folks would be the first to know.