Meal Replacement Powerful Side Effect

I have been using a PGX meal replacement called No NonSense. I only use it on occasion and not daily. I have noticed that the day I take a shake I have some... let's politely say loose movements. Reading the instructions I did note that initially my body may experience this side effect but I would have expected that I would grow accustomed to it. However, since I do not take a PGX Meal replacement everyday perhaps it is what I should expect.

I suppose I have two choice: a) scrap the No Nonsense Meal Replacements b) use it more often so my body is more used to it.