I think we can all agree that diarrhea is bad for your body. You can in fact die from it. So why do people insist on using diet products and diet supplements that are known to cause diarrhea? Because they are misinformed, that's why. Diarrhea is NOT a good way to lose weight. Once your body goes into diarrhea mode it often takes days for it to get back to normal and for some people it might not.
Diet products are not the only medical products that can cause diarrhea. One of the major ones on the market today, are colon cleansers. Those things are utterly useless. You can find all kinds of colon cleanse reviews online, most of them written by those very same companies that make the stuff.
The bottom line is, if it has diarrhea as a side effect then don't use it - period.