Irritable Bowel Syndrome (IBS) affects 10-20% of the U.S. population... and about 80% of my clinical practice's patient population. For the better part of the past decade, I've basically been living and breathing IBS in all of its forms vicariously through my patients. I know all about the incessant morning trips to the bathroom with IBS-D... the days without any activity in the bathroom with IBS-C... and the IBS-M cycles of not being able to go for days, followed by an entire day spent running to the bathroom once the "dam breaks."
There are many approaches to managing these symptoms of IBS-- from elimination diets to probiotics to other supplements to prescription medications to hypnotherapy. At one time or another, I've recommended all of these in my practice, tailoring my advice to a patient's individual pattern of symptoms.
But there are two remedies that have been the most effective for the largest number of my patients over the years: soluble fiber supplements for IBS-D and magnesium supplements for IBS-C. They're cheap, over the counter, sold everywhere, and in my humble opinion, should be the first thing you try before diving deep into the rabbit hole of expensive, extensive treatment protocols.
Citrucel and Benefiber are my soluble fiber products of choice. Taken every evening at the recommended 2g dose, they are often remarkable effective at normalizing the morning routine among people with IBS-D-- consolidating those multiple, urgent trips to the bathroom to just one or two efficient visits and forming those loose and crampy stools into bulky, complete and easy-to-pass alternatives. A full dose of Citrucel is 4 pills or 1 TBSP (orange flavored) powder. A full dose of Benefiber (unflavored) is 2 tsp. Both are equally effective. The most common way my patients describe soluble fiber therapy is "life changing."
For constipation predominant IBS, magnesium supplements at a dose of 400-800mg, also taken in the evening, can be remarkably effective in softening stools and increasing their frequency. Any old form will do, though magnesium oxide is the one you'll encounter most often. I'll usually have my patients start at 400mg and work their way up-- 200mg at a time-- if needed. Take the full dose all at once. Assuming you've got functioning kidneys, the only real side effect you need to worry about at this dose is diarrhea. If that happens, pull back on the dose to find that happy middle ground.